Transcript XML Schemas - Free University of Bozen

1
XML Schemas
Modified version of:
Roger L. Costello
XML Technologies Course (Part 1)
http://www.w3.org/TR/xmlschema-1/ (Structures)
2
Lab Exercises
• Periodically there appears an icon at the bottom, right
of the slide indicating that it is time to do a lab
exercise.
• The corresponding exercises can be found on the
website of Roger L. Costello at
http://www.w3.org/TR/xmlschema-1/
3
XML Schema Overview
• On the next few slides is a very quick, high-level
introduction to XML Schema.
• The purpose is to give the "big picture" before
jumping into all the nitty-gritty details
of creating XML schemas.
4
What is XML Schema?
An XML vocabulary
for expressing
the business rules of one’s data
5
Example
<location>
<latitude>32.904237</latitude>
<longitude>73.620290</longitude>
<uncertainty units="meters">2</uncertainty>
</location>
To be valid, this data element must meet constraints (data business rules):
1. The location must comprise a latitude,
followed by a longitude,
followed by an indication of the uncertainty of the lat/lon measurements.
2. The latitude must be a decimal with a value between -90 to +90
3. The longitude must be a decimal with a value between -180 to +180
4. For both latitude and longitude the number of digits to the right
of the decimal point must be exactly six digits.
5. The value of uncertainty must be a non-negative integer
6. The uncertainty units must be either meters or feet.
We can express all these data constraints using XML Schemas
6
Validating your data
<location>
<latitude>32.904237</latitude>
<longitude>73.620290</longitude>
<uncertainty units="meters">2</uncertainty>
</location>
XML
Declare a location element.
Require that its content be latitude, longitude, and uncertainty.
Declare a latitude element.
Require that its value be between -90 and +90.
Declare a longitude element.
Require that its value be between -180 and +180.
Declare a uncertainty element with a units attribute.
Require that the element's value be between 0 and 10.
Require that the attribute's value be either feet or meters.
XML Schema
XML Schema
validator
Data is ok!
7
What Does an XML Schema
Accomplish?
Declare a location element.
Require that its content be latitude, longitude, and
uncertainty.
Declare a latitude element.
Require that its value be between -90 and +90.
Declare a longitude element.
Require that its value be between -180 and +180.
Declare a uncertainty element with a units attribute.
Require that the element's value be between 0 and 10.
Require that the attribute's value be either feet or meters.
XML Schema
Answer:
It creates an XML vocabulary:
<location>, <latitude>, <longitude>, <uncertainty>
It specifies the contents of each element, and the restrictions
on the content.
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It Does One More Thing ...
Namespace = http://www.example.org/target
Declare a location element.
Require that its content be latitude, longitude, and uncertainty.
Declare a latitude element.
Require that its value be between -90 and +90.
Declare a longitude element.
Require that its value be between -180 and +180.
Declare a uncertainty element with a units attribute.
Require that the element's value be between 0 and 10.
Require that the attribute's value be either feet or meters.
XML Schema
An XML Schema specifies that the XML vocabulary
that is being created shall be in a "namespace"
9
http://www.example.org/target
Namespace
http://www.example.org/target
<location>
<longitude>
<latitude>
<uncertainty>
10
Constraints: in a Document
or in Middleware (code)?
• An XML Schema is an XML document.
The constraints on the data are expressed in a document.
• All of the constraints could be expressed in a programming
language (e.g., Java), in your system's middleware.
• Why express data constraints in a document?
• Answer: by expressing the data constraints in a document
(and using XML to express the constraints),
the schema itself becomes information!
Not only is the XML instance data being checked information,
but the schema itself is information.
Thus, just like the XML instance document, the schema can be
shipped around, mined, morphed, searched, etc.
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Time to Start!
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Purpose of XML Schemas
(… and DTDs)
Specify
• the structure of instance documents
“this element contains these elements, which
contains these other elements, etc.”
• the data type of each element/attribute
"this element shall hold an integer
with the range 0 to 12,000”
(DTDs don't do too well
with specifying data types like this)
13
Motivation for XML Schemas
People were dissatisfied with DTDs
• It's a different syntax
– You write your XML (instance) document using one syntax
and the DTD using another syntax
 bad, inconsistent
• Limited data type capability
– DTDs have very limited capability for specifying data types.
You can't, for example, express
"I want the <elevation> element to hold
an integer with a range of 0 to 12,000"
– Better a set of data types compatible with those in databases
• DTD supports 10 data types;
• XML Schemas supports 44+ data types
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Highlights of XML Schema
XML Schemas are an advancement over DTDs:
• Enhanced data types
– 44+ versus 10
– User-defined data types
Example: "This is a new type based on the string type and
elements of this type must follow this pattern: ddd-dddd,
where 'd' represents a digit".
• Written in the same syntax as instance documents
– less syntax to remember (although cumbersome syntax)
• Object-oriented'ish
– Can extend or restrict a type
(derive new type definitions on the basis of old ones)
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Example
We convert the BookStore.dtd (next page)
to the XML Schema syntax
• Straight, one-to-one conversion, i.e.,
Title, Author, Date, ISBN, and Publisher
will hold strings, just like is done in the DTD
• We will gradually modify the XML Schema
to use stronger types
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BookStore.dtd
<!ELEMENT BookStore (Book+)>
<!ELEMENT Book (Title, Author, Date, ISBN, Publisher)>
<!ELEMENT Title (#PCDATA)>
<!ELEMENT Author (#PCDATA)>
<!ELEMENT Date (#PCDATA)>
<!ELEMENT ISBN (#PCDATA)>
<!ELEMENT Publisher (#PCDATA)>
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ELEMENT
ATTLIST
#PCDATA
ID
NMTOKEN CDATA
ENTITY
This is the vocabulary that
DTDs provide to define your
new vocabulary
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ELEMENT
ATTLIST
#PCDATA
ID
NMTOKEN CDATA
ENTITY
This is the vocabulary that
DTDs provide to define your
new vocabulary
BookStore
Author
Book
Title
Publisher
Date
ISBN
This is the new vocabulary
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ELEMENT
ATTLIST
#PCDATA
ID
NMTOKEN CDATA
ENTITY
This is the vocabulary that
DTDs provide to define your
new vocabulary
BookStore
Author
Book
Title
Publisher
Date
ISBN
This is the new vocabulary
A difference between XML Schemas and DTDs is that the XML Schema vocabulary
is associated with a name (namespace).
Likewise, the new vocabulary that you define must be associated
with a name (namespace).
With DTDs neither set of vocabulary is associated with a name (namespace)
[because DTDs pre-dated namespaces].
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<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
(explanations on
</xsd:sequence>
succeeding pages)
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
xsd =
<xsd:element name="Publisher" type="xsd:string"/>
Xml-Schema Definition
</xsd:schema>
BookStore.xsd (see example01)
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<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<!ELEMENT BookStore
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
(Book+)>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<!ELEMENT Book
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
(Title, Author, Date,
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
ISBN, Publisher)>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<!ELEMENT Title (#PCDATA)>
<xsd:element name="Author" type="xsd:string"/>
<!ELEMENT Author (#PCDATA)>
<xsd:element name="Date" type="xsd:string"/>
<!ELEMENT Date (#PCDATA)>
<xsd:element name="ISBN" type="xsd:string"/>
<!ELEMENT ISBN (#PCDATA)>
<xsd:element name="Publisher" type="xsd:string"/>
<!ELEMENT Publisher (#PCDATA)>
</xsd:schema>
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<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:schema>
All XML schemas
have “schema”
as the root element.
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<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:schema>
The elements and
data types that
are used
to construct
schemas
- schema
- element
- complexType
- sequence
- string
come from the
namespace
http://…/XMLSchema
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XMLSchema Namespace
http://www.w3.org/2001/XMLSchema
complexType
element
sequence
schema
boolean
string
integer
25
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:schema>
Indicates that the
elements defined
by this schema
- BookStore
- Book
- Title
- Author
- Date
- ISBN
- Publisher
are to go in the
namespace
http://www.books.org
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Book Namespace (targetNamespace)
http://www.books.org (targetNamespace)
BookStore
Author
Book
Title
Publisher
Date ISBN
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<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:schema>
The default
namespace is
http://www.books.org
which is the
targetNamespace!
This is referencing a
Book element
declaration. The Book
in what namespace?
Since there is no
namespace qualifier
it is referencing the
Book element in the
default namespace,
which is the
targetNamespace!
Thus, this is a
reference to the
Book element
declaration
in this schema.
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<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="1" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Author" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Date" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="ISBN" minOccurs="1" maxOccurs="1"/>
<xsd:element ref="Publisher" minOccurs="1" maxOccurs="1"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:schema>
This is a directive to
any instance
documents
which conform
to this schema:
Any elements used
by the instance
document which
were declared in this
schema must be
namespace
qualified.
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Referencing a schema
<?xml version="1.0"?>
1
<BookStore xmlns ="http://www.books.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3
xsi:schemaLocation="http://www.books.org
BookStore.xsd">
2
<Book>
<Title>My Life and Times</Title>
<Author>Paul McCartney</Author>
<Date>July, 1998</Date>
<ISBN>94303-12021-43892</ISBN>
<Publisher>McMillin Publishing</Publisher>
</Book>
...
</BookStore>
1. The default namespace declaration tells the schemavalidator that all of the elements used in this instance
document come from the
http://www.books.org
namespace.
30
Referencing a schema
<?xml version="1.0"?>
1
<BookStore xmlns ="http://www.books.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3
xsi:schemaLocation="http://www.books.org
BookStore.xsd">
2
<Book>
<Title>My Life and Times</Title>
<Author>Paul McCartney</Author>
<Date>July, 1998</Date>
<ISBN>94303-12021-43892</ISBN>
<Publisher>McMillin Publishing</Publisher>
</Book>
...
</BookStore>
2. Attribute schemaLocation says that the
http://www.books.org
namespace is defined by BookStore.xsd
(i.e., schemaLocation contains a pair of values).
31
Referencing a schema
<?xml version="1.0"?>
1
<BookStore xmlns ="http://www.books.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3
xsi:schemaLocation="http://www.books.org
BookStore.xsd">
2
<Book>
<Title>My Life and Times</Title>
<Author>Paul McCartney</Author>
<Date>July, 1998</Date>
<ISBN>94303-12021-43892</ISBN>
<Publisher>McMillin Publishing</Publisher>
</Book>
...
</BookStore>
3. The schemaLocation attribute we are using is the one
in the XMLSchema-instance namespace.
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XMLSchema-instance Namespace
http://www.w3.org/2001/XMLSchema-instance
schemaLocation
type
noNamespaceSchemaLocation
nil
33
Referencing a schema in an
XML instance document
schemaLocation="http://www.books.org
BookStore.xsd"
BookStore.xml
- uses elements from
namespace http://www.books.org
targetNamespace="http://www.books.org"
BookStore.xsd
- defines elements in
namespace http://www.books.org
A schema defines a new vocabulary.
Instance documents use that new vocabulary.
34
Two levels of checking
BookStore.xml
BookStore.xsd
Validate that the xml document
conforms to the rules described
in BookStore.xsd
XMLSchema.xsd
(schema-for-schemas)
Validate that BookStore.xsd is a valid
schema document, i.e., it conforms
to the rules described in the
schema-for-schemas
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Default Value for
minOccurs and maxOccurs
• The default value for minOccurs is "1"
• The default value for maxOccurs is "1"
<xsd:element ref="Title" minOccurs="1" maxOccurs="1"/>
Equivalent!
<xsd:element ref="Title"/>
Do Lab1
36
Qualify XMLSchema,
Default targetNamespace
In the first example, we explicitly qualified all elements
from the XML Schema namespace.
The targetNamespace was the default namespace.
http://www.w3.org/2001/XMLSchema
complexType
http://www.books.org (targetNamespace)
BookStore
element
Author
sequence
schema
Book
Title
string
boolean
Publisher ISBN
Date
integer
37
Default XMLSchema,
Qualify targetNamespace
Alternatively (equivalently), we can design our schema
so that XMLSchema is the default namespace.
http://www.w3.org/2001/XMLSchema
complexType
element
http://www.books.org (targetNamespace)
BookStore
Author
sequence
schema
Book
Title
string
integer
boolean
Publisher ISBN
Date
38
<?xml version="1.0"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns:bk="http://www.books.org"
elementFormDefault="qualified">
<element name="BookStore">
<complexType>
<sequence>
<element ref="bk:Book" maxOccurs="unbounded"/>
</sequence>
</complexType>
</element>
<element name="Book">
<complexType>
<sequence>
<element ref="bk:Title"/>
<element ref="bk:Author"/>
<element ref="bk:Date"/>
<element ref="bk:ISBN"/>
<element ref="bk:Publisher"/>
</sequence>
</complexType>
</element>
<element name="Title" type="string"/>
<element name="Author" type="string"/>
<element name="Date" type="string"/>
<element name="ISBN" type="string"/>
<element name="Publisher" type="string"/>
</schema>
(see example02)
Note that
http://…/XMLSchema
is the
default namespace.
Consequently, there
are no namespace
qualifiers on
- schema
- element
- complexType
- sequence
- string
39
<?xml version="1.0"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns:bk="http://www.books.org"
elementFormDefault="qualified">
<element name="BookStore">
<complexType>
<sequence>
<element ref="bk:Book" maxOccurs="unbounded"/>
</sequence>
</complexType>
</element>
<element name="Book">
<complexType>
<sequence>
<element ref="bk:Title"/>
<element ref="bk:Author"/>
<element ref="bk:Date"/>
<element ref="bk:ISBN"/>
<element ref="bk:Publisher"/>
</sequence>
</complexType>
</element>
<element name="Title" type="string"/>
<element name="Author" type="string"/>
<element name="Date" type="string"/>
<element name="ISBN" type="string"/>
<element name="Publisher" type="string"/>
</schema>
(see example02)
Here we are
referencing a
Book element.
Where is that
Book element
defined?
In what namespace?
The bk: prefix
indicates what
namespace this
element is in.
“bk:” has been set to
be the same as the
targetNamespace.
40
“bk:” References the
targetNamespace
http://www.w3.org/2001/XMLSchema
http://www.books.org
(targetNamespace)
BookStore
complexType
element
Author
Book
sequence
schema
string
Title
boolean
Date
integer
bk
Publisher
ISBN
Do Lab1.1
Consequently, bk:Book refers to the Book element in the targetNamespace.
41
Inlining Element Declarations
• In the previous examples we declared an element
and then we ref ’ed to that element declaration.
Alternatively, we can inline the element declarations.
• On the following slide is an alternate (equivalent) way
of representing the schema shown previously,
using inlined element declarations.
42
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
Note that we have
elementFormDefault="qualified">
moved all the
<xsd:element name="BookStore">
element
<xsd:complexType>
declarations
<xsd:sequence>
inline,
<xsd:element name="Book" maxOccurs="unbounded">
and we are no
<xsd:complexType>
<xsd:sequence>
longer ref'ing to
<xsd:element name="Title" type="xsd:string"/>
the element
<xsd:element name="Author" type="xsd:string"/>
declarations.
<xsd:element name="Date" type="xsd:string"/>
This results in a
<xsd:element name="ISBN" type="xsd:string"/>
much more
<xsd:element name="Publisher" type="xsd:string"/>
compact schema!
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
(see example03)
Designing a schema by inlining everything is called the Russian Doll design.
43
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
Anonymous
</xsd:element>
(no name)
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
(see example03)
types
Do Lab 2
44
Named Types
The following slide shows
an alternate (equivalent) schema
which uses a named complexType.
45
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
The advantage
targetNamespace="http://www.books.org"
of splitting out
xmlns="http://www.books.org"
Book's
elementFormDefault="qualified">
element
<xsd:element name="BookStore">
declarations
<xsd:complexType>
and wrapping
<xsd:sequence>
<xsd:element name="Book" type="BookPublication" them in a
named type is
maxOccurs="unbounded"/>
that now this
</xsd:sequence>
Named type
type can be
</xsd:complexType>
reused by
</xsd:element>
other elements.
<xsd:complexType name="BookPublication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
(see example04)
</xsd:schema>
46
type Attribute or complexType
Child Element, but not both!
An element declaration can have a type attribute,
or a complexType child element,
but it cannot have both
• a type attribute and
• a complexType child element.
<xsd:element name="A" type="foo">
<xsd:complexType>
…
</xsd:complexType>
</xsd:element>
47
Summary of Declaring
Elements (two ways to do it)
1
<xsd:element name="name" type="type"
minOccurs="int"
maxOccurs="int"/>
A simple type
(e.g., xsd:string)
A nonnegative
or the name of
integer
a complexType
(e.g., BookPublication)
A nonnegative
integer
or "unbounded"
Note: minOccurs and maxOccurs can only
be used in nested (local) element declarations.
48
Summary of Declaring
Elements (two ways to do it)
1
<xsd:element name="name" type="type"
minOccurs="int"
maxOccurs="int"/>
2
<xsd:element name="name" minOccurs="int" maxOccurs="int">
<xsd:complexType>
…
</xsd:complexType>
</xsd:element>
49
Problem
• Defining the Date element to be of type string is unsatisfactory
(it allows any string value to be input as the content of the Date
element, including non-date strings).
– Constrain the allowable content that Date can have.
Modify the BookStore schema to restrict the content of the
Date element to just date values
(actually, year values; see next two slides).
• Similarly, constrain the content of the ISBN element to content
of this form:
– d-ddddd-ddd-d or
– d-ddd-ddddd-d or
– d-dd-dddddd-d,
where 'd' stands for 'digit'
50
The date Data Type
• A built-in data type
(i.e., schema validators know about this data type)
• Used to represent a specific day (year-month-day)
• Elements declared to be of type date must follow this form:
CCYY-MM-DD
– range for CC is: 00-99
– range for YY is: 00-99
– range for MM is: 01-12
– range for DD is:
• 01-28 if month is 2
• 01-29 if month is 2 and the gYear is a leap gYear
• 01-30 if month is 4, 6, 9, or 11
• 01-31 if month is 1, 3, 5, 7, 8, 10, or 12
Example: 1999-05-31 represents May 31, 1999
51
The gYear Data Type
• A built-in data type (Gregorian calendar year)
• Elements declared to be of type gYear
must follow this form: CCYY
– range for CC is: 00-99
– range for YY is: 00-99
Example: 1999 indicates the gYear 1999
52
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:simpleType name="ISBNType">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\d{1}-\d{5}-\d{3}-\d{1}"/>
<xsd:pattern value="\d{1}-\d{3}-\d{5}-\d{1}"/>
<xsd:pattern value="\d{1}-\d{2}-\d{6}-\d{1}"/>
</xsd:restriction>
</xsd:simpleType>
Here we are defining a new
(user-defined) data-type, called ISBNType.
(see example05)
53
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:gYear"/>
<xsd:element name="ISBN" type="ISBNType"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Declaring Date to be of type gYear,
and ISBN to be of type ISBNType (defined above)
(see example05)
54
<xsd:simpleType name="ISBNType">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\d{1}-\d{5}-\d{3}-\d{1}"/>
<xsd:pattern value="\d{1}-\d{3}-\d{5}-\d{1}"/>
<xsd:pattern value="\d{1}-\d{2}-\d{6}-\d{1}"/>
</xsd:restriction>
</xsd:simpleType>
"I hereby declare a new type called ISBNType. It is a restricted form of
the string type. Elements declared of this type must conform to one of the following patterns:
- First Pattern: 1 digit followed by a dash followed by 5
digits followed by another dash followed by 3 digits followed by
another dash followed by 1 more digit, or
- Second Pattern: 1 digit followed by a dash followed by 3
digits followed by another dash followed by 5 digits followed by
another dash followed by 1 more digit, or
- Third Pattern: 1 digit followed by a dash followed by 2
digits followed by another dash followed by 6 digits followed by
another dash followed by 1 more digit."
These patterns are specified using Regular Expressions.
In a few slides we will see more of the Regular Expression syntax.
55
Equivalent Expressions
<xsd:simpleType name="ISBNType">
<xsd:restriction base="xsd:string">
<xsd:pattern value=“\d{1}-\d{5}-\d{3}-\d{1}“ />
<xsd:pattern value=“\d{1}-\d{3}-\d{5}-\d{1}“ />
<xsd:pattern value=“\d{1}-\d{2}-\d{6}-\d{1}“ />
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="ISBNType">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\d{1}-\d{5}-\d{3}-\d{1}
|\d{1}-\d{3}-\d{5}-\d{1}
| \d{1}-\d{2}-\d{6}-\d{1}"/>
</xsd:restriction>
</xsd:simpleType>
The vertical bars means "or"
56
<xsd:complexType> or
<xsd:simpleType>?
When do you use the complexType element and when
do you use the simpleType element?
– Use the complexType element when you want to
define child elements and/or attributes of an
element
– Use the simpleType element when you want to
create a new type that is a refinement of a built-in
type (string, date, gYear, etc)
57
Built-in Data Types
Primitive data types
– string
– boolean
– decimal
– float
– double
– duration
– dateTime
– time
– date
– gYearMonth
– gYear
– gMonthDay
Atomic, built-in
– "Hello World"
– {true, false, 1, 0}
– 7.08
– 12.56E3, 12, 12560, 0, -0, INF, -INF, NAN
– 12.56E3, 12, 12560, 0, -0, INF, -INF, NAN
– P1Y2M3DT10H30M12.3S
– format: CCYY-MM-DDThh:mm:ss
– format: hh:mm:ss.sss
– format: CCYY-MM-DD
– format: CCYY-MM
– format: CCYY
– format: --MM-DD
Note: 'T' is the date/time separator
INF = infinity
NAN = not-a-number
58
Built-in Data Types (cont.)
Primitive data types
– gDay
– gMonth
– hexBinary
– base64Binary
– anyURI
– QName
– NOTATION
Atomic, built-in
– format: ---DD (note the 3 dashes)
– format: --MM
– a hex string
– a base64 string
– http://www.xfront.com
– a namespace qualified name
– a NOTATION from the XML spec
59
Built-in Data Types (cont.)
•
Derived types
– normalizedString
– token
– language
– IDREFS
– ENTITIES
– NMTOKEN
– NMTOKENS
– Name
– NCName
– ID
– IDREF
– ENTITY
– integer
– nonPositiveInteger
•
Subtype of primitive data type
– A string without tabs, line feeds, or carriage returns
– String w/o tabs, l/f, leading/trailing spaces
– any valid xml:lang value, e.g., EN, FR, ...
– must be used only with attributes
– must be used only with attributes
– must be used only with attributes
– must be used only with attributes
– XML names
– non-colonized name (no namespace qualifier)
– must be used only with attributes
– must be used only with attributes
– must be used only with attributes
– 456
– negative infinity to 0
60
Built-in Data Types (cont.)
•
Derived types
– negativeInteger
– long
– int
– short
– byte
– nonNegativeInteger
– unsignedLong
– unsignedInt
– unsignedShort
– unsignedByte
– positiveInteger
•
Subtype of primitive data type
–
negative infinity to -1
– -9223372036854775808 to 9223372036854775807
– -2147483648 to 2147483647
– -32768 to 32767
– -127 to 128
– 0 to infinity
– 0 to 18446744073709551615
– 0 to 4294967295
– 0 to 65535
– 0 to 255
– 1 to infinity
Note: the following types can only be used with attributes (which we will discuss later):
ID, IDREF, IDREFS, NMTOKEN, NMTOKENS, ENTITY, and ENTITIES.
Do Lab 3
61
Creating Your Own Data Types
• A new data type can be defined from an existing data type
(called the "base" type) by specifying values for one or more of
the optional facets for the base type.
• Example. The string primitive data type has six optional facets:
– length
– minLength
– maxLength
– pattern
– enumeration
– whitespace (legal values: preserve, replace, collapse)
62
Creating a New Data Type by
Specifying Facet Values
<xsd:simpleType name="TelephoneNumber">
<xsd:restriction base="xsd:string"> 2
<xsd:length value="8"/> 3
<xsd:pattern value="\d{3}-\d{4}"/> 4
</xsd:restriction>
</xsd:simpleType>
1
1. This creates a new data type called 'TelephoneNumber'.
2. Elements of this type can hold string values,
3. But the string length must be exactly 8 characters long and
4. The string must follow the pattern: ddd-dddd, where 'd' represents a 'digit'.
(In this example the regular expression makes the length facet redundant.)
63
Enumeration Types
<xsd:simpleType name="shape">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="circle"/>
<xsd:enumeration value="triangle"/>
<xsd:enumeration value="square"/>
</xsd:restriction>
</xsd:simpleType>
This creates a new type called shape.
An element declared to be of this type
must have either the value circle, or triangle, or square.
64
Facets of the integer Data Type
• The integer data type has 8 optional facets:
– totalDigits
– pattern
– whitespace
– enumeration
– maxInclusive
– maxExclusive
– minInclusive
– minExclusive
65
Example
<xsd:simpleType name= "EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
This creates a new data type called 'EarthSurfaceElevation'.
Elements declared to be of this type can hold an integer.
However, the integer is restricted to have a value between
-1290 and 29035, inclusive.
General Form of Creating a New Data
Type by Specifying Facet Values
<xsd:simpleType name= "name">
<xsd:restriction base= "xsd:source">
<xsd:facet value= "value"/>
<xsd:facet value= "value"/>
…
</xsd:restriction>
</xsd:simpleType>
Facets:
- length
- minlength
- maxlength
- pattern
- enumeration
- minInclusive
- maxInclusive
- minExclusive
- maxExclusive
...
Sources:
- string
- boolean
- number
- float
- double
- duration
- dateTime
- time
...
66
67
Multiple Facets – “and”ed or “or”ed?
<xsd:simpleType name="TelephoneNumber">
<xsd:restriction base="xsd:string">
<xsd:length value="8"/>
<xsd:pattern value="\d{3}-\d{4}"/>
</xsd:restriction>
</xsd:simpleType>
An element declared to be of type TelephoneNumber
must be a string of length=8 and the string must
follow the pattern: 3 digits, dash, 4 digits.
68
Multiple Facets – “and”ed or
“or”ed?
<xsd:simpleType name="shape">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="circle"/>
<xsd:enumeration value="triangle"/>
<xsd:enumeration value="square"/>
</xsd:restriction>
</xsd:simpleType>
An element declared to be of type shape must be a string
with a value of either circle, or triangle, or square.
Patterns, enumerations => "or" them together
All other facets => "and" them together
69
Creating a simpleType from
Another simpleType
• Thus far we have created a simpleType using one of
the built-in data types as our base type.
• However, we can create a simpleType that uses
another simpleType as the base. See next slide.
70
<xsd:simpleType name= "EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name= "BostonAreaSurfaceElevation">
<xsd:restriction base="EarthSurfaceElevation">
<xsd:minInclusive value="0"/>
<xsd:maxInclusive value="120"/>
</xsd:restriction>
</xsd:simpleType>
This simpleType uses EarthSurfaceElevation as its base type.
71
Fixing a Facet Value
Sometimes when defining a simpleType we want to require
that one (or more) facets have an unchanging value.
That is, we want to make the facet a constant.
<xsd:simpleType name= "ClassSize">
<xsd:restriction base="xsd:nonNegativeInteger">
<xsd:minInclusive value="10" fixed="true"/>
<xsd:maxInclusive value="60"/>
simpleTypes which
</xsd:restriction>
derive from this
</xsd:simpleType>
simpleType may
not change this facet.
72
<xsd:simpleType name= "ClassSize">
<xsd:restriction base="xsd:nonNegativeInteger">
<xsd:minInclusive value="10" fixed="true"/>
<xsd:maxInclusive value="60"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name= "BostonIEEEClassSize">
<xsd:restriction base="ClassSize">
<xsd:minInclusive value="15"/>
<xsd:maxInclusive value="60"/>
Error! Cannot
</xsd:restriction>
change the value
</xsd:simpleType>
of a fixed facet!
73
Element Containing a
User-Defined Simple Type
Example. Create a schema element declaration for an elevation element.
Declare the elevation element to be an integer with a range -1290 to 29035
<elevation>5240</elevation>
Here's one way of declaring the elevation element:
<xsd:simpleType name="EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:element name="elevation" type="EarthSurfaceElevation"/>
74
Element Containing a
User-Defined Simple Type (cont.)
Here's an alternative method for declaring elevation:
<xsd:element name="elevation">
<xsd:simpleType>
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
The simpleType definition is
defined inline, it is an
anonymous
simpleType definition.
The disadvantage of this
approach is that this
simpleType may not be
reused by other elements.
75
Summary of Declaring
Elements (three ways to do it)
1
<xsd:element name="name" type="type"
minOccurs="int"
maxOccurs="int"/>
2
<xsd:element name="name" minOccurs="int" maxOccurs="int">
<xsd:complexType>
…
</xsd:complexType>
</xsd:element>
76
Summary of Declaring
Elements (three ways to do it)
3
<xsd:element name="name" minOccurs="int" maxOccurs="int">
<xsd:simpleType>
<xsd:restriction base="type">
…
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
77
Annotating Schemas
• The <annotation> element is used for documenting the schema,
both for humans and for machines.
– Use <documentation> for providing a comment to humans
– Use <appinfo> for providing a comment to machines
• The content is any well-formed XML
• Note that annotations have no effect on schema validation
<xsd:annotation>
<xsd:documentation>
The following constraint is not expressible with XML Schema:
The value of element A should be greater
than the value of element B.
We will express this constraint in the appinfo section (below).
</xsd:documentation>
<xsd:appinfo>
<assert test="A &gt; B">A should be greater than B</assert>
</xsd:appinfo>
<xsd:/annotation>
78
Where Can You Put
Annotations?
• You cannot put annotations at just any random
location in the schema.
• Here are the rules for where an annotation element
can go:
– annotations may occur
before and after any global component
– annotations may occur
only at the beginning of non-global components
79
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Suppose that you want to annotate, say, the Date element
declaration. What do we do? See next page ...
Can put
annotations
only at
these
locations
80
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string">
<xsd:annotation>
<xsd:documentation>This is how to annotate the Date element!
</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Inline the annotation within the Date element declaration.
81
Two Optional Attributes for the
documentation Element
In the previous example we showed
<xsd:documentation>
with no attributes. Actually, it can have two attributes:
• source: this attribute contains a URL to a file which
contains supplemental information
• xml:lang: this attribute specifies the language that the
documentation was written in
<xsd:documentation
source="http://www.xfront.com/BookReview.txt"
xml:lang="FR"/>
82
One Optional Attribute for the
appinfo Element
In the previous example we showed
<xsd:appinfo>
with no attributes.
Actually, it can have one attribute:
source: this attribute contains a URL to a file which
contains supplemental information
<xsd:appinfo source="http://www.xfront.com/Assertions.xml"/>
83
The Big Picture
• Let's back up for a moment and look at XML
Schemas from a "big picture" point of view.
84
Saving Code Using XML Schemas
Code to actually
do the work
Code to check the
structure and content
(data type) of the data
"In a typical program, up to 60% of the code is spent checking the data!"
- source unknown
Continued -->
85
Saving Code Using XML Schemas
(cont.)
Code to actually
do the work
Code to check the
structure and content
of the data
If your data is structured as
XML, and there is a schema,
then you can hand the
data-checking task off to a
schema validator.
Thus, your code is reduced
by up to 60%!!!
86
Classic Use of XML Schemas
(Trading Partners - B2B)
Software
to process
P.O.
"P.O. is
okay"
P.O.
P.O.
Consumer
Supplier
Schema
Validator
P.O = Purchase Order
P.O.
Schema
(Schema at third-party, neutral web site)
87
What are XML Schemas?
Data Model
• With XML Schemas you specify how your XML data
will be organized, and the data types of your data.
That is, with XML Schemas you model how your data
is to be represented in an instance document.
A Contract
• Organizations agree to structure their XML
documents in conformance with an XML Schema.
Thus, the XML Schema acts as a contract between
the organizations.
88
XML Schemas Contain Metadata
An XML Schema document contains lots of data about
the data in the XML instance documents, such as
• the data type of the data,
• the data's range of values,
• how the data is related to another piece of data
(parent/child, sibling relationship)
89
XML Schema  GUI
P.O.
Schema
GUI
Builder
P.O.
HTML
Supplier
Web
Server
90
XML Schema  API
P.O.
Schema
API
Builder
P.O.
API
91
XML Schema  Smart Editor
P.O.
Schema
Smart Editor
(e.g.,
XML Spy)
Helps you build your
instance documents.
For example, it pops
up a menu showing
you what is valid next.
It knows this by looking
at the XML Schema!
92
Automatic
API generation
Validate
XML
documents
XML Schema
Smart Editor
Automatic
GUI generation
Semantic Web???
Do Lab 4
93
Regular Expressions
Recall that the string data type has a pattern facet.
The value of a pattern facet is a regular expression.
Below are some examples of regular expressions:
Regular Expression
Example
- Chapter \d
- Chapter&#x020;\d
- a*b
- [xyz]b
- a?b
- a+b
- [a-c]x
- Chapter 1
- Chapter 1
- b, ab, aab, aaab, …
- xb, yb, zb
- b, ab
- ab, aab, aaab, …
- ax, bx, cx
94
Regular Expressions in XML
Schema
• XML Schema has its own flavour of reg. exp.s
•
limited features
•
only for validation, not for extraction
•
allow for efficient processing
(“text-directed engines” = det. fin. automata)
– disjunction only at top level
95
Regular Expressions (cont.)
Regular Expression
– [a-c]x
– [-ac]x
– [ac-]x
– [^0-9]x
– \Dx
– Chapter\s\d
– (ho){2} there
– (ho\s){2} there
– .abc
Example
– ax, bx, cx
– -x, ax, cx
– ax, cx, -x
– any non-digit char followed by x
– any non-digit char followed by x
– Chapter followed by a blank
followed by a digit
– hoho there
– ho ho there
– any (one) char followed by abc
96
Regular Expressions (cont.)
• a{1,3}x
• a{2,}x
• \w\s\w
•
•
•
ax, aax, aaax
aax, aaax, aaaax, …
word character (alphanumeric plus dash)
followed by a space followed by a word
character
•
[a-zA-Z-[Ol]]*
•
A string comprised of any lower and upper
case letters, except "O" and "l"
•
\.
•
The period "."
(Without the backward slash the period
means "any character")
97
Regular Expressions (cont.)
•
•
•
•
•
•
•
•
•
•
•
•
\n
\r
\t
\\
\|
\\^
\?
\*
\+
\(
\)
•
•
•
•
•
•
•
•
•
•
•
•
linefeed
carriage return
tab
The backward slash \
The vertical bar |
The hyphen The caret ^
The question mark ?
The asterisk *
The plus sign +
The open paren (
The close paren )
98
Regular Expressions
• \p{L}
• \p{Lu}
•
•
•
•
•
\p{Ll}
\p{N}
\p{Nd}
\p{P}
\p{Sc}
• A letter, from any language
• An uppercase letter, from any
language
• A lowercase letter, from any language
• A number - Roman, fractions, etc
• A digit from any language
• A punctuation symbol
• A currency sign, from any language
99
Regular Expressions (concluded)
<xsd:simpleType name="money">
<xsd:restriction base="xsd:string">
<xsd:pattern value="\p{Sc}\p{Nd}+(\.\p{Nd}\p{Nd})?"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:element name="cost" type="money"/>
currency sign from any language,
followed by
one or more digits from any language,
optionally followed by
a period and
two digits from any language
<cost>$45.99</cost>
<cost>¥300</cost>
100
Example R.E.
[1-9]?[0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]
0 to 99
100 to 199 200 to 249 250 to 255
What does this mean?
Where could it be used?
101
IP Data Type Definition
<xsd:simpleType name="IP">
<xsd:restriction base="xsd:string">
<xsd:pattern value="(([1-9]?[0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3}
([1-9]?[0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])">
<xsd:annotation>
<xsd:documentation>
data type for representing IP addresses. Examples,
129.83.64.255, 64.128.2.71, etc.
This data type restricts each field of the IP address
to have a value between zero and 255, i.e.,
[0-255].[0-255].[0-255].[0-255]
Note: in the value attribute (above) the regular
expression has been split over two lines. This is
for readability purposes only. In practice the R.E.
would all be on one line.
</xsd:documentation>
</xsd:annotation>
</xsd:pattern>
</xsd:restriction>
</xsd:simpleType>
102
Regex for different platform
line breaks?
Different systems use different line break characters.
<?xml version="1.0"?> \r\n
<Test> \r\n
<para xml:space="preserve">This is a \r\n
simple paragraph. What \r\n
do you think of it?</para> \r\n
</Test> \r\n
An XML parser "normalizes" all line breaks.
After normalization the XML document looks like this:
<?xml version="1.0"?> \n
<Test> \n
<para xml:space="preserve">This is a \n
simple paragraph. What \n
do you think of it?</para> \n
</Test> \n
103
Regex for different platform
line breaks?
Note:
1. All line breaks have been normalized to \n.
Consequence: you don't have to be concerned about different platforms
using different line break characters since all XML documents will have
their line break characters normalized to \n regardless of the
platform. (So, if you're writing an XML Schema regex expression you can
simply use \n to indicate line break, regardless of the platform.)
2. The xml:space="preserve" attribute has no impact on line break
normalization.
3. Suppose that you want a line break character in your XML document,
other than \n. For example, suppose that you want \r in your XML
Do Lab 5
document. By default, it would get normalized to \n. To prevent this,
use a character reference: &#xD;
104
Derived Types
Two forms of subclassing complexType definitions
• by extension: extend the parent complexType
with more elements
• by restriction: create a type that is
a subset of the base type.
Two ways to subset the elements:
– redefine a base type element
to have a restricted range of values, or
– redefine a base type element
to have a more restricted number of occurrences
105
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:complexType name="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="BookPublication">
<xsd:complexContent>
<xsd:extension base="Publication" >
<xsd:sequence>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" type="BookPublication"
maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Note that
BookPublication
extends
the Publication
type, i.e.,
we are doing
Derive by
Extension
(see example06)
106
<xsd:complexType name="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType >
<xsd:complexType name="BookPublication">
<xsd:complexContent>
<xsd:extension base="Publication">
<xsd:sequence>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType >
Elements declared to be of type BookPublication will have 5 child elements Title, Author, Date, ISBN, and Publisher.
The elements in the derived type are
appended to the elements in the base type.
107
ISBN
Title
Date
Author
Publication
BookPublication
Publisher
108
Publication
Title
Author
Date
"extends"
BookPublication
ISBN
Publisher
Do Lab 6
109
Derive by Restriction
<xsd:complexType name="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name= "SingleAuthorPublication">
<xsd:complexContent>
<xsd:restriction base="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:restriction>
</xsd:complexContent> Elements of type SingleAuthorPublication
</xsd:complexType>
will have 3 child elements –
Title, Author, and Date.
there must be exactly one Author element.
110
Deleting an Element in the Base Type
<xsd:complexType name="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" minOccurs="0"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name= "ZeroAuthorPublication">
<xsd:complexContent>
<xsd:restriction base="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
In this subtype we have eliminated the Author
</xsd:restriction>
</xsd:complexContent>
element, i.e., the subtype is just comprised of an
</xsd:complexType>
unbounded number of Title elements followed by
single Date element.
If the base type has an element with minOccurs="0",
and the subtype wishes to not have that element,
then it can simply leave it out.
a
111
Derive by Restriction (cont.)
•
Question
– why do I have to repeat all the declarations from the base type? Why can't I
simply show the delta (i.e., show those declarations that are changed)?
– What's the advantage of doing derived by restriction if I have to repeat
everything? I'm certainly not saving on typing.
•
Answer:
– Even though you have to retype everything in the base type there are
advantages to explicitly associating a type with a base type.
In a few slides we will see element substitution - the ability to substitute one
element for another. A restriction of element substitution is that the
substituting element have a type that derives from the type of the element it
is substituting. Thus, it is beneficial to link the type.
– Also, later we will see that an element’s content model may be substituted
by the content model of derived types. Thus, the content of an element that
has been declared to be of type Publication can be substituted with a
SingleAuthorPublication content since SingleAuthorPublication derives from
Publication. We will discuss this type substitutability in detail later.
112
Prohibiting Derivations
•
•
Sometimes we may want to create a type and disallow all derivations of it, or just
disallow extension derivations, or disallow restriction derivations.
Rationale: "For example, I may create a complexType and make it publicly
available for others to use. However, I don't want them to extend it with their
proprietary extensions or subset it to remove, say, copyright information." (Jon
Cleaver)
<xsd:complexType name="Publication" final="#all" …>
Publication cannot be extended nor restricted
<xsd:complexType name="Publication" final="restriction" …>
Publication cannot be restricted
<xsd:complexType name="Publication" final="extension" …>
Publication cannot be extended
113
Terminology: Declaration vs Definition
In a schema:
• You declare elements and attributes.
Schema components that are declared are those that
have a representation in an XML instance document.
• You define components that are used just within the
schema document(s).
Schema components that are defined are those that
have no representation in an XML instance
document.
Declarations:
- element declarations
- attribute declarations
Definitions:
- type (simple, complex) definitions
- attribute group definitions
- model group definitions
114
Global versus Local
• Global element declarations, global type definitions:
– These are element declarations/type definitions
that are immediate children of <schema>
• Local element declarations, local type definitions:
– These are element declarations/type definitions
that are nested within other elements/types.
115
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
elementFormDefault="qualified">
<xsd:complexType name="Publication">
Global type definition
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="BookPublication">
Global type definition
<xsd:complexContent>
<xsd:extension base="Publication" >
<xsd:sequence>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:element name="BookStore">
Global element declaration
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" type="BookPublication" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
Local element declarations
</xsd:schema>
Local type definition
116
Global vs Local …
What's the Big Deal?
Question:
So what if an element or type is global or local.
What practical impact does it have?
Answer:
Only global elements/types can be referenced
(i.e., reused).
Thus, if an element/type is local then it is effectively
invisible to the rest of the schema
(and to other schemas).
117
Element Substitution
Oftentimes in daily conversation there are several ways
to express something.
• In Boston we use the words "T" and "subway" interchangeably. For
example, "we took the T into town", or "we took the subway into town".
• Thus, "T" and "subway" are substitutable. Which one is used may depend
upon what part of the state you live in, what mood you're in, or any number
of factors.
• We would like to be able to express this substitutability in XML Schemas.
• Thus, we would like to be able to declare in a schema an element called
"subway", an element called "T", and state that "T" may be substituted for
"subway". Instance documents can then use either <subway> or <T>,
depending on their preference.
118
substitutionGroup
We can define a group of substitutable elements
(called a substitutionGroup)
by declaring an element (called the head) and then
declaring other elements which state that they are substitutable for
the head element.
<xsd:element name="subway" type="xsd:string"/>
<xsd:element name="T" substitutionGroup="subway" type="xsd:string"/>
subway is the head element
T is substitutable for subway
Anywhere a head element can be used in an instance document,
any member of the substitutionGroup can be substituted!
119
Schema:
<xsd:element name="subway" type="xsd:string"/>
<xsd:element name="T" substitutionGroup="subway" type="xsd:string"/>
<xsd:element name="transportation">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="subway"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
Instance
doc:
<transportation>
<subway>Red Line</subway>
</transportation>
<transportation>
<T>Red Line</T>
</transportation>
Alternative
instance doc
(substitute T
for subway):
This example shows the <subway> element
being substituted with the <T> element.
120
International Clients
• We can use substitutionGroups to create elements
customized for our international clients.
On the next slide is shown a Spanish version of the
element.
121
<xsd:element name="subway" type="xsd:string"/>
<xsd:element name="metro" substitutionGroup="subway" type="xsd:string"/>
<xsd:complexType name="transport">
<xsd:sequence>
Schema:
<xsd:element ref="subway"/>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="transportation" type="transport"/>
<xsd:element name="transporte" substitutionGroup="transportation"/>
Instance <transportation>
<subway>Red Line</subway>
doc:
</transportation>
<transportation>
<metro>Linea Roja</metro>
</transportation>
Alternative
instance doc
(customized
for Spanish clients):
122
Notes About Using
substitutionGroup
• The elements that are declared to be in the
substitution group (e.g., subway and T) must be
declared as global elements
• If the type of a substitutionGroup element is the same
as the head element then you can omit it (the type)
In our Subway example we could have omitted the
type attribute in the declaration of the T element
since it is the same as Subway’s type (xsd:string).
<xsd:element name="T" substitutionGroup="subway"/>
123
Notes about using
substitutionGroup (cont.)
• The type of every element in the substitutionGroup
must be the same as, or derived from, the type of the
head element.
<xsd:element name="A" type="xxx"/>
<xsd:element name="B" substitutionGroup="A" type="yyy"/>
This type must be the same as "xxx" or,
it must be derived from "xxx".
124
Element Substitution with
Derived Types
<xsd:element name="Publication" type="PublicationType"/>
<xsd:element name="Book" substitutionGroup="Publication"
type="BookType"/>
<xsd:element name="Magazine" substitutionGroup="Publication"
type="MagazineType"/>
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Publication" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
125
BookType and MagazineType
Derive from PublicationType
PublicationType
BookType
MagazineType
In order for Book and Magazine to be in a substitutionGroup with
Publication, their type (BookType and MagazineType, respectively)
must be the same as, or derived from Publication's type (PublicationType)
126
<xsd:complexType name="PublicationType">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string" minOccurs="0" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="BookType">
<xsd:complexContent>
<xsd:extension base="PublicationType" >
<xsd:sequence>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:complexType name="MagazineType">
<xsd:complexContent>
<xsd:restriction base="PublicationType">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:restriction>
</xsd:complexContent>
</xsd:complexType>
127
<?xml version="1.0"?>
<BookStore …>
<Book>
<Title>Illusions: The Adventures of a Reluctant Messiah</Title>
<Author>Richard Bach</Author>
<Date>1977</Date>
<ISBN>0-440-34319-4</ISBN>
<Publisher>Dell Publishing Co.</Publisher>
</Book>
<Magazine>
<Title>Natural Health</Title>
<Date>1999</Date>
</Magazine>
<Book>
<Title>The First and Last Freedom</Title>
<Author>J. Krishnamurti</Author>
<Date>1954</Date>
<ISBN>0-06-064831-7</ISBN>
<Publisher>Harper &amp; Row</Publisher>
</Book>
</BookStore>
<BookStore> can contain any element in the substitutionGroup with Publication!
128
Blocking Element Substitution
• An element may wish to block other elements from
substituting with it.
• This is achieved by adding a block attribute.
<xsd:element name="…" type="…" block="substitution"/>
129
Schema:
Instance doc:
Not allowed!
<xsd:element name="subway" type="xsd:string" block="substitution"/>
<xsd:element name="T" substitutionGroup="subway"/>
<xsd:element name="transportation">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="subway"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<transportation>
<subway>Red Line</subway>
</transportation>
<transportation>
<T>Red Line</T>
</transportation>
There is no error in declaring T to be substitutable with subway.
The error occurs only when you try to do substitution in the instance document.
130
One More Note About
substitutionGroup
1. Transitive:
If element A can substitute for element B, and
element B can substitute for element C,
then element A can substitute for element C.
A --> B --> C then A --> C
2. Non-symmetric:
If element A can substitute for element B,
it is not the case that element B can substitute for element A.
Do Lab 7
131
Attributes
• On the next slide we see a version of the BookStore
DTD that uses attributes.
• Then, on the following slide we see
how this is implemented using XML Schemas.
132
<!ELEMENT BookStore (Book+)>
<!ELEMENT Book (Title, Author, Date, ISBN, Publisher)>
<!ATTLIST Book
Category (autobiography | non-fiction | fiction) #REQUIRED
InStock (true | false) "false"
Reviewer CDATA " ">
<!ELEMENT Title (#PCDATA)>
<!ELEMENT Author (#PCDATA)>
<!ELEMENT Date (#PCDATA)>
<!ELEMENT ISBN (#PCDATA)>
<!ELEMENT Publisher (#PCDATA)>
BookStore.dtd
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
<xsd:attributeGroup ref="BookAttributes"/>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:attributeGroup name="BookAttributes">
<xsd:attribute name="Category" use="required">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="autobiography"/>
<xsd:enumeration value="non-fiction"/>
<xsd:enumeration value="fiction"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="InStock" type="xsd:boolean" default="false"/>
<xsd:attribute name="Reviewer" type="xsd:string" default=" "/>
</xsd:attributeGroup>
133
Category
(autobiography
| non-fiction
| fiction)
#REQUIRED
InStock (true
| false)
"false"
Reviewer
CDATA " "
(see example07)
134
<xsd:attribute name="Category" use="required">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="autobiography"/>
<xsd:enumeration value="non-fiction"/>
<xsd:enumeration value="fiction"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
• “Instance documents are required to have the Category attribute
(as indicated by use="required").”
• “The value of Category must be either
autobiography, non-fiction, or fiction
(as specified by the enumeration facets)."
Note: attributes can only have simpleTypes
(i.e., attributes cannot have child elements).
135
Summary of Declaring
Attributes (2 ways to do it)
1 <xsd:attribute name="name" type="simple-type"
use="how-its-used"
default/fixed="value"/>
xsd:string
xsd:integer
xsd:boolean
...
required
optional
prohibited
The "use" attribute
must be
optional if you use
default or fixed.
136
Summary of Declaring
Attributes (2 ways to do it)
2
<xsd:attribute name="name" use="how-its-used" default/fixed="value">
<xsd:simpleType>
<xsd:restriction base="simple-type">
<xsd:facet value="value"/>
…
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
137
use="prohibited"
Question: When would use="prohibited" be used?
Answer: Useful when you create a master type that lists all possible
attributes, and then subtypes can delete the attributes that are not needed.
<xsd:complexType name="shape">
<xsd:attribute name="length" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="height" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="width" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="radius" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="diameter" type="xsd:nonNegativeInteger"/>
</xsd:complexType>
<xsd:complexType name="box">
<xsd:complexContent>
<xsd:restriction base="shape">
<xsd:attribute name="length" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="height" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="width" type="xsd:nonNegativeInteger"/>
<xsd:attribute name="radius" type="xsd:nonNegativeInteger" use="prohibited"/>
<xsd:attribute name="diameter" type="xsd:nonNegativeInteger" use="prohibited"/>
</xsd:restriction>
</xsd:complexContent>
</xsd:complexType>
138
use  Use it Only with Local
Attribute Declarations
• The "use" attribute only makes sense
in the context of an element declaration.
Example: “For each Book element,
the Category attribute is required".
• When declaring a global attribute
do not specify a "use"
139
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
…
</xsd:sequence>
<xsd:attribute ref="Category" use="required"/>
…
</xsd:complexType>
</xsd:element>
<xsd:attribute name="Category">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="autobiography"/>
<xsd:enumeration value="fiction"/>
<xsd:enumeration value="non-fiction"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
Local attribute declaration.
Use the “use” attribute here.
Global attribute declaration.
Must NOT have a "use"
(“use” only makes sense in
the context of an element)
140
Inlining Attributes
There another way of expressing the last example
• the attributes are inlined within the Book declaration
• rather than being separately defined in an
attributeGroup
141
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
<xsd:attribute name="Category" use="required">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="autobiography"/>
<xsd:enumeration value="non-fiction"/>
<xsd:enumeration value="fiction"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="InStock" type="xsd:boolean" default="false"/>
<xsd:attribute name="Reviewer" type="xsd:string" default=" "/>
</xsd:complexType>
</xsd:element>
(see example08)
142
Notes about Attributes
• The attribute declarations always come last, after the
element declarations.
• The attributes are always with respect to the element
that they are defined (nested) within.
"bar and boo are
attributes of foo"
<xsd:element name="foo">
<xsd:complexType>
<xsd:sequence>
…
</xsd:sequence>
<xsd:attribute name="bar" …/>
<xsd:attribute name="boo" …/>
</xsd:complexType>
</xsd:element>
143
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
These attributes
<xsd:attribute name="Category" use="required">
apply to the
<xsd:simpleType>
element they are
<xsd:restriction base="xsd:string">
nested within (Book)
<xsd:enumeration value="autobiography"/>
That is, Book has three
<xsd:enumeration value="non-fiction"/>
attributes –
<xsd:enumeration value="fiction"/>
Category, InStock,
</xsd:restriction>
and Reviewer.
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="InStock" type="xsd:boolean" default="false"/>
<xsd:attribute name="Reviewer" type="xsd:string" default=" "/>
</xsd:complexType>
</xsd:element>
Do Lab 8.a,
144
Element with Simple Content
and Attributes
Example.
<elevation units="feet">5440</elevation>
The elevation element has these two constraints:
- it has a simple (integer) content
- it has an attribute called units
How do we declare elevation?
145
<xsd:element name="elevation">
<xsd:complexType> 1
<xsd:simpleContent> 2
<xsd:extension base="xsd:integer"> 3
<xsd:attribute name="units" type="xsd:string" use="required"/>
4
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
1. elevation contains an attribute
— therefore, we must use <xsd:complexType>
2. However, elevation does not contain child elements
(which is what we generally use <complexType> to indicate).
Instead, elevation contains simpleContent.
3. We wish to extend the simpleContent (an integer) ...
4. … with an attribute.
146
Elevation: Use Stronger Data Type
• In the declaration for elevation
we allowed it to hold any integer.
Further, we allowed the units attribute
to hold any string.
• Let's restrict elevation to hold
– an integer with a range 0  12,000 and
– let's restrict units to hold either
the string “feet” or the string “meters”
147
<xsd:simpleType name="elevationRange">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="0"/>
<xsd:maxInclusive value="12000"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:simpleType name="unitsType">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="feet"/>
<xsd:enumeration value="meters"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:element name="elevation">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="elevationRange">
<xsd:attribute name="units" type="unitsType" use="required"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
148
Equivalent!
<xsd:element name="elevation">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="elevationRange">
<xsd:attribute name="units" type="unitsType" use="required"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
<xsd:complexType name="elevationType">
<xsd:simpleContent>
<xsd:extension base="elevationRange">
<xsd:attribute name="units" type="unitsType" use="required"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
<xsd:element name="elevation" type="elevationType"/>
149
Extending simpleContent
<xsd:simpleType name= "EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:complexType name="SurfaceElevation">
<xsd:simpleContent>
<xsd:extension base="EarthSurfaceElevation">
<xsd:attribute name="units" type="xsd:string" fixed="feet"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
<xsd:element name="DenverElevation" type="SurfaceElevation"/>
<DenverElevation units="feet">______</DenverElevation
value must be between -1290 and 29035
150
Restricting simpleContent
SurfaceElevation
<xsd:simpleType name= "EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
Value space:
-1290 to 29035
Attribute: units
(fixed at “feet”)
restrict the value space
BostonAreaSurfaceElevation
Value space:
0 to 120
Attribute: units
(fixed at “feet”)
<xsd:simpleType name="BostonAreaEarthSurfaceElevation">
<xsd:restriction base="EarthSurfaceElevation">
<xsd:minInclusive value="0"/>
<xsd:maxInclusive value="120"/>
</xsd:restriction>
</xsd:simpleType>
151
Restricting simpleContent
<xsd:complexType name="BostonAreaSurfaceElevation">
<xsd:simpleContent>
<xsd:restriction base="SurfaceElevation">
<xsd:simpleType>
<xsd:restriction base="BostonAreaEarthSurfaceElevation"/>
</xsd:simpleType>
</xsd:restriction>
</xsd:simpleContent>
</xsd:complexType>
<xsd:element name="BostonElevation" type="BostonAreaSurfaceElevation"/>
<BostonElevation units="feet">______</BostonElevation
value must be between 0 and 120
(see example08.1)
152
Extending simpleContent vs
Restricting simpleContent
<xsd:complexType name="...">
<xsd:simpleContent>
<xsd:extension base="Y1">
Z1
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
<xsd:complexType name="...">
<xsd:simpleContent>
<xsd:restriction base="Y2">
Z2
</xsd:restriction>
</xsd:simpleContent>
</xsd:complexType>
Y1 must be a simpleType
(either built-in or user-defined).
Z1 must be one or more
attribute declarations.
Y2 must be a complexType
with simpleContent.
Z2 must be a simpleType
(either built-in or user-defined).
153
Declaring Elements: Summary
1. Element with simple content
Declaring an element using a built-in type:
<xsd:element name="numStudents" type="xsd:positiveInteger"/>
Declaring an element using a user-defined simpleType:
<xsd:simpleType name="shapes">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="triangle"/>
<xsd:enumeration value="rectangle"/>
<xsd:enumeration value="square"/>
</xsd:restriction>
</xsd:simpleType>
<xsd:element name="geometry" type="shapes"/>
154
Declaring Elements: Summary
An alternative formulation of the above shapes example is
to inline the simpleType definition:
<xsd:element name="geometry">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="triangle"/>
<xsd:enumeration value="rectangle"/>
<xsd:enumeration value="square"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
155
Declaring Elements: Summary
2. Element contains child elements
Defining the child elements inline:
<xsd:element name="Person">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="FirstName" type="xsd:string"/>
<xsd:element name="Surname" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
156
Declaring Elements: Summary
An alternate formulation of the above Person example is
to create a named complexType and then use that type:
<xsd:complexType name="PersonType">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="FirstName" type="xsd:string"/>
<xsd:element name="Surname" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="Person" type="PersonType"/>
157
Declaring Elements: Summary
3. Element contains a complexType that is
an extension of another complexType
<xsd:complexType name="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="BookPublication">
<xsd:complexContent>
<xsd:extension base="Publication" >
<xsd:sequence>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:element name="Book" type="BookPublication"/>
158
Declaring Elements: Summary
4. Element contains a complexType that is
a restriction of another complexType
<xsd:complexType name="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name= "SingleAuthorPublication">
<xsd:complexContent>
<xsd:restriction base="Publication">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:gYear"/>
</xsd:sequence>
</xsd:restriction>
</xsd:complexContent>
</xsd:complexType>
<xsd:element name="Catalogue" type="SingleAuthorPublication"/>
159
Declaring Elements: Summary
5. Element Contains Simple Content and Attributes
<xsd:element name="apple">
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="xsd:string">
<xsd:attribute name="variety" type="xsd:string" use="required"/>
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
</xsd:element>
Example.
<apple variety="Cortland">Large, green, sour</apple>
160
complexContent vs simpleContent
• With complexContent
you extend or restrict a complexType
• With simpleContent
you extend or restrict a simpleType
<xsd:complexType name="…">
<xsd:complexContent>
<xsd:extension base="X">
…
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
X must be a complexType
vs.
<xsd:complexType name="…">
<xsd:simpleContent>
<xsd:extension base="Y">
…
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
Y must be a simpleType
161
group Element
• The group element enables you
to group together element declarations.
• Note: the group element is just for grouping together
element declarations,
no attribute declarations allowed!
162
<xsd:element name="Book" >
<xsd:complexType>
<xsd:sequence>
<xsd:group ref="PublicationElements"/>
<xsd:element name="ISBN" type="string"/>
<xsd:element name="Reviewer" type="string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="CD" >
<xsd:complexType>
<xsd:sequence>
<xsd:group ref="PublicationElements"/>
<xsd:element name="RecordingStudio" type="string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:group name="PublicationElements">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string" maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:string"/>
</xsd:sequence>
</xsd:group>
An example showing the use of the <group> element
163
Group definitions must be global
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:group name="PublicationElements">
<xsd:sequence>
<xsd:element name="Title" type="xsd:string" minOccurs="0"/>
<xsd:element name="Author" type="xsd:string" minOccurs="0"
maxOccurs="unbounded"/>
<xsd:element name="Date" type="xsd:string"/>
</xsd:sequence>
</xsd:group>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
...
</xsd:complexType>
</xsd:element>
One cannot inline the group definition.
Instead, one must use a ref here and
define the group globally.
164
Expressing Alternates
DTD: <!ELEMENT transportation (train | plane | automobile)>
XML Schema:
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.travel.org"
xmlns="http://www.travel.org"
elementFormDefault="qualified">
<xsd:element name="transportation">
<xsd:complexType>
<xsd:choice>
<xsd:element name="train" type="xsd:string"/>
<xsd:element name="plane" type="xsd:string"/>
<xsd:element name="automobile" type="xsd:string"/>
</xsd:choice>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Note: the choice is an exclusive-or, that is, transportation can contain
only one element — either train, or plane, or automobile.
(see example10)
165
Repeatable Choice
DTD:
XML Schema:
<!ELEMENT binary-string (zero | one)*>
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.binary.org"
xmlns="http://www.binary.org"
elementFormDefault="qualified">
<xsd:element name="binary-string">
<xsd:complexType>
<xsd:choice minOccurs="0" maxOccurs="unbounded">
<xsd:element name="zero" type="xsd:unsignedByte" fixed="0"/>
<xsd:element name="one" type="xsd:unsignedByte" fixed="1"/>
</xsd:choice>
</xsd:complexType>
</xsd:element>
</xsd:schema>
1. An element can fix its value, using the fixed attribute.
2. When you don't specify a value for minOccurs, it defaults to "1".
Same for maxOccurs. See the transportation example.
(see example 11)
166
fixed/default Element Values
When you declare an element
you can give it a fixed or default value.
 In the instance document,
you can leave the element empty.
<element name="zero"
fixed="0"/>
…
<zero>0</zero>
or equivalently:
<zero/>
<element name="color"
default="red"/>
…
<color>red</color>
or equivalently:
<color/>
167
Using <sequence> and <choice>
DTD:
XML
Schema:
<!ELEMENT life ((work, eat)*, (work | play), sleep)* >
<xsd:element name="life">
<xsd:complexType>
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:sequence minOccurs="0" maxOccurs="unbounded">
<xsd:element name="work" type="xsd:string"/>
<xsd:element name="eat" type="xsd:string"/>
</xsd: sequence>
<xsd:choice>
<xsd:element name="work" type="xsd:string"/>
<xsd:element name="play" type="xsd:string"/>
</xsd:choice>
<xsd:element name="sleep" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
168
Expressing Any Order
Create an element, Book, which contains Author, Title, Date, ISBN, Publisher,
in any order (This is very difficult and ugly with DTDs).
XML
Schema:
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:all>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:all>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<all> means that Book must contain all five child elements,
but they may occur in any order
(see example 12)
169
Constraints on using <all>
• Elements declared within <all> must have a
maxOccurs value of "1"
(minOccurs can be either "0" or "1")
• If a complexType uses <all> and it extends another
type, then that parent type must have empty content.
• The <all> element cannot be nested within either
<sequence>, <choice>, or another <all>
• The contents of <all> must be just elements. It
cannot contain <sequence> or <choice>
Do Lab 9
170
Empty Element
<!ELEMENT image EMPTY>
<!ATTLIST image href CDATA #REQUIRED>
DTD:
Schema:
<xsd:element name="gallery">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="image" maxOccurs="unbounded">
<xsd:complexType>
<xsd:attribute name="href" type="xsd:anyURI" use="required"/>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
Instance
doc
(snippet):
<image href="http://www.xfront.com/InSubway.gif"/>
Do Lab 10
(see example 13)
Summary of Defining simpleTypes
1. simpleType that uses a built-in base type:
<xsd:simpleType name= "EarthSurfaceElevation">
<xsd:restriction base="xsd:integer">
<xsd:minInclusive value="-1290"/>
<xsd:maxInclusive value="29035"/>
</xsd:restriction>
</xsd:simpleType>
Summary of Defining simpleTypes
2. simpleType that uses another simpleType
as the base type:
<xsd:simpleType name= "BostonSurfaceElevation">
<xsd:restriction base="EarthSurfaceElevation">
<xsd:minInclusive value="0"/>
<xsd:maxInclusive value="120"/>
</xsd:restriction>
</xsd:simpleType>
Summary of Defining simpleTypes
3. simpleType that defines a list type:
<xsd:simpleType name= "LotteryNumbers">
<xsd:list itemType="OneToNinetyNine"/>
</xsd:simpleType>
where the data type OneToNinetyNine is declared as:
<xsd:simpleType name= "OneToNinetyNine">
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxInclusive value="99"/>
</xsd:restriction>
</xsd:simpleType>
Summary of Defining simpleTypes
4. An alternate form of the previous, where the list's
data type is specified using an inlined simpleType:
<xsd:simpleType name= "LotteryNumbers">
<xsd:list>
<xsd:simpleType>
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxInclusive value="99"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:list>
</xsd:simpleType>
Summary of Defining simpleTypes
5. simpleType that defines a union type:
<xsd:simpleType name= "maxOccurs">
<xsd:union memberTypes="xsd:nonNegativeInteger UnboundedType"/>
</xsd:simpleType>
where the data type UnboundedType is declared as:
<xsd:simpleType name= "UnboundedType">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="unbounded"/>
</xsd:restriction>
</xsd:simpleType>
Summary of Defining simpleTypes
6. An alternate form of the previous,
where the data type UnboundedType is specified
using an inline simpleType:
<xsd:simpleType name= "maxOccurs">
<xsd:union memberTypes="xsd:nonNegativeInteger">
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="unbounded"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:union>
</xsd:simpleType>
Uniqueness and Keys
DTDs provide the ID attribute data type for uniqueness
XML Schema enables one to:
• define element content to be unique
• define non-ID attributes to be unique
• define a combination of element content and attributes to
be unique
• distinguish between unique versus key
• declare the range of the document
over which something is unique
unique vs key
Key: an element or attribute (or combination thereof)
which is defined to be a key must:
• always be present
(minOccurs must be greater than zero)
• be non-nillable (i.e., nillable="false")
• be unique
nil in XML Schema is
like null in SQL
Key implies unique, but
unique does not imply key
Example: ISBN as a Key
• When a book is published it has an ISBN,
which is guaranteed to be unique
• In the BookStore we should be able to express that
each Book's ISBN element is unique
• Further, let's make the ISBN elements keys
(i.e., both unique and required to exist)
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
xmlns:bk="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
<xsd:key name="PK">
<xsd:selector xpath="bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:key>
</xsd:element>
</xsd:schema>
(see example32)
<xsd:element name="BookStore">
...
<xsd:key name="PK">
<xsd:selector xpath="bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:key>
</xsd:element>
• “Within <BookStore> we define a key, called PK.
Select the <Book> elements,
and for each <Book> the ISBN element is a
key.”
• In other words:
within <BookStore>, each <Book> must have
an <ISBN> and it must be unique.
• Note: We are using the content of a field as a key!
No longer limited to ID attributes!
<?xml version="1.0"?>
<BookStore xmlns="http://www.books.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://www.books.org
BookStore.xsd">
<Book>
<Title>My Life and Times</Title>
<Author>Paul McCartney</Author>
<Date>1998</Date>
<ISBN>1-56592-235-2</ISBN>
<Publisher>McMillin Publishing</Publisher>
</Book>
<Book>
<Title>Illusions The Adventures of a Reluctant Messiah</Title>
<Author>Richard Bach</Author>
<Date>1977</Date>
<ISBN>0-440-34319-4</ISBN>
<Publisher>Dell Publishing Co.</Publisher>
</Book>
<Book>
<Title>The First and Last Freedom</Title>
<Author>J. Krishnamurti</Author>
<Date>1954</Date>
<ISBN>0-06-064831-7</ISBN>
<Publisher>Harper &amp; Row</Publisher>
</Book>
</BookStore>
A schema-validator
will verify that each
Book has an ISBN
element and that the
values are all unique.
(see example32)
Notes about <key>
• A key must be nested within an <element>
• A key must come at the end of <element>
(after the content model, and attribute declarations)
• The <key> element has a <selector> child,
which selects the set of elements
for which the key applies.
• The <key> element has a <field> child,
that identifies the element or attribute
that is to be the key
There can be multiple <field> elements.
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.CostelloReunion.org"
xmlns="http://www.CostelloReunion.org"
xmlns:reunion="http://www.CostelloReunion.org"
elementFormDefault="qualified">
<xsd:element name="FamilyReunion">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Participants" >
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Name" minOccurs="0" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="First" type="xsd:string"/>
<xsd:element name="Last" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
The key is the
combination of
the First and
Last name.
<xsd:key name="PK">
<xsd:selector xpath="reunion:Participants/reunion:Name"/>
<xsd:field xpath="reunion:First"/>
<xsd:field xpath="reunion:Last"/>
</xsd:key>
</xsd:element>
</xsd:schema>
<?xml version="1.0"?>
<FamilyReunion xmlns="http://www.CostelloReunion.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://www.CostelloReunion.org
FamilyReunion.xsd">
<Participants>
<Name><First>Peter</First><Last>Brown</Last></Name>
<Name><First>Peter</First><Last>Costello</Last></Name>
</Participants>
</FamilyReunion>
A schema-validator will verify that
each First name/Last name combination
is unique.
xPath Expressions must be
Namespace-qualified
(when elementFormDefault="qualified")
Note: we namespace-qualified the xPath references:
<xsd:key name="PK">
<xsd:selector xpath="bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:key>
Required, even though the targetNamespace is the
default namespace: This is an xPath requirement.
Note: If the schema had instead set
elementFormDefault ="unqualified",
then the xPath expressions would not be namespace-qualified.
Uniqueness Constraints
• The element
<unique>
is used exactly like the <key> element.
It has
– a <selector>
– one or more <field> elements
• The only difference is that the schema validator will
simply validate that, whenever present, the values
are unique.
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.books.org"
xmlns="http://www.books.org"
xmlns:bk="http://www.books.org"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string" minOccurs="0"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
<xsd:unique name="UNIQ">
<xsd:selector xpath="bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:unique>
</xsd:element>
</xsd:schema>
Note: ISBN
is optional
Require
ISBNs
to be unique
<?xml version="1.0"?>
<BookStore xmlns="http://www.books.org/namespaces/BookStore"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://www.books.org/namespaces/BookStore
BookStore24.xsd">
<Book>
<Title>My Life and Times</Title>
<Author>Paul McCartney</Author>
<Date>1998</Date>
<Publisher>McMillin Publishing</Publisher>
</Book>
<Book>
<Title>Illusions The Adventures of a Reluctant Messiah</Title>
<Author>Richard Bach</Author>
<Date>1977</Date>
<ISBN>0-440-34319-4</ISBN>
<Publisher>Dell Publishing Co.</Publisher>
</Book>
<Book>
<Title>The First and Last Freedom</Title>
<Author>J. Krishnamurti</Author>
<Date>1954</Date>
<ISBN>0-06-064831-7</ISBN>
<Publisher>Harper &amp; Row</Publisher>
</Book>
</BookStore>
A schema-validator
will verify that
each Book
that has an ISBN
element
has a unique value
(note that
the first Book
does not have
an ISBN)
Referencing a key
• In DTDs, by declaring an attribute of type IDREF,
that attribute must reference an ID attribute
• An XML Parser will verify that the IDREF value
corresponds to a legitimate ID value
• Similarly, one can define a keyref constraint,
which asserts,
“the value of this element
must match the value of an element
referred to by this“
Referential Integrity
key element
<?xml version="1.0"?>
<Library xmlns="http://www.library.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.library.org AuthorSigningAtLibrary.xsd">
<Books>
<Book>
<Title>Illusions The Adventures of a Reluctant Messiah</Title>
<Author>Richard Bach</Author>
<Date>1977</Date>
Suppose we define
<ISBN>0-440-34319-4</ISBN>
<Publisher>Dell Publishing Co.</Publisher>
ISBN to be a
</Book>
key for Book
...
</Books>
<GuestAuthors>
<Author>
<Name>Richard Bach</Name>
<BookForSigning>
<Title>Illusions The Adventures of a Reluctant Messiah</Title>
<ISBN>0-440-34319-4</ISBN>
</BookForSigning>
We want to ensure that the
</Author>
ISBN for the GuestAuthor
</GuestAuthors>
</Library>
matches one of the ISBNs
A keyref element
in the BookStore
<xsd:element name="Library">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Books">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
What are keyrefs
</xsd:element>
called in
<xsd:element ref="GuestAuthors"/>
relational databases?
</xsd:sequence>
</xsd:complexType>
<xsd:key name="PK">
<xsd:selector xpath="bk:Books/bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:key>
<xsd:keyref name="isbnRef" refer="PK">
<xsd:selector xpath="bk:GuestAuthors/bk:Author/bk:BookForSigning"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:keyref>
</xsd:element>
AuthorSigningAtLibrary.xsd (snippet, see example35)
<xsd:key name="PK">
<xsd:selector xpath="bk:BookStore/bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:key>
Tells the schema-validator to validate
that every Book (in BookStore) has an ISBN,
and the ISBN is unique.
<xsd:keyref name="isbnRef" refer="PK">
<xsd:selector xpath="bk:GuestAuthors/bk:Author/bk:BookForSigning"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:keyref>
This tells the schema-validator that the ISBN of the Book
that the Author is signing must refer to one of the ISBN
elements in the collection defined by the PK key.
key and keyref
• If there are 2 fields in the key,
then there must be 2 fields in the keyref,
if there are 3 fields in the key,
then there must be 3 fields in the keyref,
etc.
• Further, the fields in the keyref must match the key
in type and position
Specifying scope of uniqueness in
XML Schemas
• The key/keyref/unique elements may be placed
anywhere in a schema
(that is, at the bottom of any element declaration)
• Where they are placed determines
the scope of the uniqueness
Example.
• We may desire to have uniqueness in a localized
region of instance documents.
• Thus, we would use key/keyref/unique within the
element for that region.
nil Content
Empty content vs nil:
• Empty: an element with an empty content never has content
• nil: an instance document element may indicate no value is available
by setting an attribute - xsi:nil - equal to 'true'
XML Schema:
<xsd:element name="PersonName">
<xsd:complexType>
<xsd:element name="forename" type="xsd:NMTOKEN"/>
<xsd:element name="middle" type="xsd:NMTOKEN" nillable="true"/>
<xsd:element name="surname" type="xsd:NMTOKEN"/>
</xsd:complexType>
</xsd:element>
XML instance
document:
<PersonName>
<forename>John</forename>
<middle xsi:nil="true"/>
<surname>Doe</surname>
</PersonName>
The content of middle
can be a NMTOKEN value or
its content can be undefined.
No targetNamespace
(noNamespaceSchemaLocation)
• Sometimes you may wish to create a schema but
without associating the elements with a namespace.
• The targetNamespace attribute is actually an optional
attribute of <schema>. Thus, if you don’t want to
specify a namespace for your schema then simply
don’t use the targetNamespace attribute.
• Consequences of having no namespace
– In the instance document don’t namespace
qualify the elements.
– In the instance document, instead of using
schemaLocation use
noNamespaceSchemaLocation.
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xsd:element name="BookStore">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" minOccurs="0" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Title"/>
<xsd:element ref="Author"/>
<xsd:element ref="Date"/>
<xsd:element ref="ISBN"/>
<xsd:element ref="Publisher"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:schema>
There is no
targetNamespace
attribute, and
there is no longer a
default namespace.
(see example14)
<?xml version="1.0"?>
<BookStore xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation= "BookStore.xsd">
<Book>
<Title>My Life and Times</Title>
<Author>Paul McCartney</Author>
<Date>1998</Date>
<ISBN>1-56592-235-2</ISBN>
<Publisher>McMillin Publishing</Publisher>
</Book>
…
</BookStore>
(see example14)
1. There is no default namespace declaration.
So, none of the elements are associated with a namespace.
2. We do not use xsi:schemaLocation (since it requires a pair of values –
a namespace and a URL to the schema for that namespace).
Instead, we use xsi:noNamespaceSchemaLocation.
Assembling an Instance Document from
Multiple Schema Documents
• An instance document may be composed of
elements from multiple schemas.
• Validation can apply to the entire XML instance
document, or to a single element.
<?xml version="1.0"?>
Validating against
<Library xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
two schemas
xsi:schemaLocation=
"http://www.book.org Book.xsd
http://www.employee.org Employee.xsd">
The <Book> elements are
<Books>
<Book xmlns="http://www.book.org">
defined in Book.xsd, and
<Title>My Life and Times</Title>
the <Employee> elements
<Author>Paul McCartney</Author>
are defined in Employee.xsd.
<Date>1998</Date>
The <Library>, <Books>,
<ISBN>1-56592-235-2</ISBN>
and <Employees> elements
<Publisher>Macmillan Publishing</Publisher>
are not defined in any schema!
</Book>
</Books>
1. A schema validator will
<Employees>
<Employee xmlns="http://www.employee.org">
validate each Book element
<Name>John Doe</Name>
against Book.xsd.
<SSN>123-45-6789</SSN>
2. It will validate each
</Employee>
Employee element against
<Employee xmlns="http://www.employee.org">
Employee.xsd.
<Name>Sally Smith</Name>
3. It will not validate the other
<SSN>000-11-2345</SSN>
elements.
</Employee>
</Employees>
Library.xml
</Library>
(see example 15)
Lax vs Strict Validation
• On the previous slide there were elements (Library,
Books, and Employees) for which there was no schema
to validate against.
• Lax validation is where the schema validator skips over
elements for which no schema is available.
• Strict validation is where the schema validator requires
validation of every element
• Most validators perform strict validation,
while some can be told to perform lax validation.
Assembling a Schema from Multiple
Schema Documents
The include element allows you to access components in other schemas
• All the schemas you include must have the same namespace as your
schema (i.e., the schema that is doing the include)
• The net effect of include is as though you had typed all the definitions
directly into the containing schema
LibraryEmployee.xsd
LibraryBook.xsd
<xsd:schema …>
<xsd:include schemaLocation="LibraryBook.xsd"/>
<xsd:include schemaLocation="LibraryEmployee.xsd"/>
…
</xsd:schema>
Library.xsd
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.library.org"
xmlns="http://www.library.org"
elementFormDefault="qualified">
<xsd:include schemaLocation="LibraryBook.xsd"/>
<xsd:include schemaLocation="LibraryEmployee.xsd"/>
<xsd:element name="Library">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Books">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Book" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Employees">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Employee" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Library.xsd
These are
referencing
element
declarations
in the other
schemas.
(see example 16)
Assembling a Schema from
a Schema with no targetNamespace
• A schema can <include> another schema which has
no targetNamespace
• The included components take on the
targetNamespace of the schema that is doing the
<include>
• This is called the Chameleon Effect
• The components in the no-namespace schema are
called Chameleon components
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xsd:complexType name="ProductType">
<xsd:sequence>
<xsd:element name="Type" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>
Product.xsd
(see example17)
This schema has no targetNamespace!
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.company.org"
xmlns="http://www.company.org"
elementFormDefault="qualified">
<xsd:include schemaLocation="Person.xsd"/>
<xsd:include schemaLocation="Product.xsd"/>
<xsd:element name="Company">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Person" type="Person" maxOccurs="unbounded"/>
<xsd:element name="Product" type="ProductType" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Company.xsd
(see example17)
This schema <include>s Product.xsd.
Thus, the components in Product.xsd are namespace-coerced
to the company targetNamespace.
Consequently, we can reference those components just as though
they had originally been declared in a schema with the same
targetNamespace.
Assembling a Schema from Multiple Schema
Documents with Different Namespaces
The import element allows you to access elements
and types in a different namespace
Namespace
B
Namespace
A
B.xsd
A.xsd
<xsd:schema …>
<xsd:import namespace="A"
schemaLocation="A.xsd"/>
<xsd:import namespace="B"
schemaLocation="B.xsd"/>
…
</xsd:schema>
C.xsd
Camera Schema
Nikon.xsd
Olympus.xsd
Camera.xsd
Pentax.xsd
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.nikon.com"
xmlns="http://www.nikon.com"
Nikon.xsd
elementFormDefault="qualified">
<xsd:complexType name="body_type">
<xsd:sequence>
<xsd:element name="description" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.olympus.com"
xmlns="http://www.olympus.com"
Olympus.xsd
elementFormDefault="qualified">
<xsd:complexType name="lens_type">
<xsd:sequence>
<xsd:element name="zoom" type="xsd:string"/>
<xsd:element name="f-stop" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.pentax.com"
Pentax.xsd
xmlns="http://www.pentax.com"
elementFormDefault="qualified">
<xsd:complexType name="manual_adapter_type">
<xsd:sequence>
<xsd:element name="speed" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema>
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" These import
elements give
targetNamespace="http://www.camera.org"
xmlns:nikon="http://www.nikon.com"
us access to
xmlns:olympus="http://www.olympus.com"
the components
xmlns:pentax="http://www.pentax.com"
in these other
elementFormDefault="qualified">
schemas.
<xsd:import namespace="http://www.nikon.com"
schemaLocation="Nikon.xsd"/>
<xsd:import namespace="http://www.olympus.com"
Here we are using
schemaLocation="Olympus.xsd"/>
the body_type that
<xsd:import namespace="http://www.pentax.com"
is defined in the
schemaLocation="Pentax.xsd"/>
<xsd:element name="camera">
Nikon namespace
<xsd:complexType>
<xsd:sequence>
<xsd:element name="body" type="nikon:body_type"/>
<xsd:element name="lens" type="olympus:lens_type"/>
<xsd:element name="manual_adapter" type="pentax:manual_adapter_type"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:schema>
Camera.xsd
(see example 18)
<?xml version="1.0"?>
<c:camera xmlns:c="http://www.camera.org"
xmlns:nikon="http://www.nikon.com"
xmlns:olympus="http://www.olympus.com"
xmlns:pentax="http://www.pentax.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://www.camera.org
Camera.xsd">
<c:body>
<nikon:description>Ergonomically designed casing
for easy handling
</nikon:description>
</c:body>
<c:lens>
<olympus:zoom>300mm</olympus:zoom>
<olympus:f-stop>1.2</olympus:f-stop>
</c:lens>
<c:manual_adapter>
<pentax:speed>1/10,000 sec to 100 sec</pentax:speed>
</c:manual_adapter>
</c:camera>
Camera.xml
any Element
The <any> element enables the instance document author to extend
his/her document with elements not specified by the schema.
<xsd:element name="Book">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string"/>
<xsd:element name="Publisher" type="xsd:string"/>
<xsd:any minOccurs="0"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
Now an instance document author can optionally extend
(after <Publisher>) the content of <Book> elements with any element.
<?xml version="1.0"?>
<BookStore xmlns="http://www.BookRetailers.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://www. BookRetailers.org
BookSeller.xsd
http://www.repository.org
SchemaRepository.xsd">
This instance
<Book>
document uses
<Title>My Life and Times</Title>
components from
<Author>Paul McCartney</Author>
two different
<Date>1998</Date>
schemas.
<ISBN>94303-12021-43892</ISBN>
<Publisher>McMillin Publishing</Publisher>
<Reviewer xmlns="http://www.repository.org">
<Name>
<First>Roger</First>
<Last>Costello</Last>
</Name>
</Reviewer>
</Book>
</BookStore>
Extensible Instance Documents
• The <any> element enables instance document
authors to create instance documents containing
elements above and beyond what was specified by
the schema.
• The instance documents are said to be extensible.
Contrast this schema with previous schemas where
the content of all our elements were always fixed and
static.
• We are empowering the instance document author
with the ability to define what data makes sense to
him/her!
Mixed Content
• An element that contains a mix of elements and (string)
data is called "mixed content".
• Mixed content has many applications.
XSLT uses mixed content frequently in template rules,
e.g.,
<xsl:template match="Book">
The title of the book is:
<xsl:value-of select="Title/text()"/>
The author of the book is:
<xsl:value-of select="Author/text()"/>
</xsl:template>
The content of
the xsl:template element
is a mix of string data
and elements.
Specifying Mixed Content when
Declaring an Element
• The <complexType> element has an optional
attribute, mixed
• By default, mixed="false"
• To specify that an element can have mixed content
use
<complexType mixed="true">
<?xml version="1.0"?>
<Letter xmlns="http://www.letter.org"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://www.letter.org Letter.xsd">
<Body>
Dear Sirs:
This letter is to inform you that we are
finding your tool <emp> very </emp> useful.
</Body>
</Letter>
Letter.xml
(see example36)
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.letter.org"
xmlns="http://www.letter.org"
elementFormDefault="qualified">
<xsd:element name="Letter">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Body">
<xsd:complexType mixed="true">
<xsd:sequence>
<xsd:element name="emp" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
Letter.xsd
(see example36)
Limitations of XML Schema
Some conditions cannot be expressed in XML Schema:
• Ensure that the value of the aircraft <Elevation> element
is greater than the value of the obstacle <Height> element.
• Ensure that:
– if the value of the attribute mode is "air",
then the value of the element <Transportation>
is either airplane or hot-air balloon
– if mode="water"
then <Transportation> is either boat or hovercraft
• Ensure that the value of the <PaymentReceived>
is equal to the value of <PaymentDue>
What have these examples in common?