Transcript Natix - Al Akhawayn University

Natix
Done by
Asmaa Hassanain
CSC 5370
Dr. Hachim Haddoutti
12/8/2003
Contents
XML data management Techniques
What is Natix
Natix Architecture
Storage Layer: Logical Data Model
Mapping between XML and the Logical Model
XML page Interpreter Storage Formater
XML segment mapping for large trees
Index Structures
Natix Physical Algebra
Example Plans
To do...
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XML data management
Techniques
 Map data to relational database
 But:
 Store data as a plain text file
 Unnormalized relations
 But:
Data as
centric
view: Large number
 Storedata
objects
 Need to parse the entire file for
of
tables
 But:
processing every query
 Designing
Nativecentric
XML database
 Document
all
OOD systems are view:
not enough
systemsinformantion
from
scratch
a single
data item
developed to in
provide
efficient
querying
capabilities
(e.g.
CLOB)
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Natix
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What is Natix?
 Natix is a native XML Repository
 Proposed by Kanne and Moerkotte at
University of Mannheim (Germany)
 Natix requires Linux to run (kernel
2.2.16 or later, or 2.4.*), with CODA
support enabled in the kernel.
 Still under development
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Natix Architecture
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Natix Architecture
Binding Layer: map between the Natix
Engine Interface and different
application interfaces
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Natix Architecture
e. g. NatixFS:
 File system interface – Natix can be mounted like
an ordinary file system
 Allows to view XML tree as a file system tree
 Importing a document – just copy it to a
directory, e.g. cp bib.xml /natix
 Exporting a document – just open it, e.g.
more /natix/bib.xml
 Removing a document – just delete a file, e.g.
rm /natix/bib.xml
 XPath expressions – just use it as file name, e.g.
more /natix/{%%title}
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Natix Architecture
Service Layer: Provides all DBMS
functionality required in addition to
simple storage and retrieval
 Natix Engine Interface
 Query execution engine
 Query compiler
 Transaction manager
 Object manager
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Natix Architecture
Natix Engine Interface:
 The interface through which the
database services communicate with
each other and with applications
 provides a unified facade to specify
requests to the database system.
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Natix Architecture
Query compiler: translates queries
expressed in XML query languages
into optimized query execution plans
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Natix Architecture
Query execution engine: evaluates
queries
 Interprets the plan passed by the
query compiler
 Able to execute all queries
expressible in a typical XML query
language like XQuery
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Natix Architecture
Transaction management : contains
classes that provide ACIDstyle
transactions + Components for
recovery
 adapt the ARIES protocol for
recovery
 For synchronization, an S2PLbased
scheduler is introduced
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Natix Architecture
Storage Layer: manages all persistent data
structures and their transfer between main
and secondary memory .
 contains classes for efficient XML storage,
indexes and metadata storage.
 manages the storage of the recovery log and
controls the transfer of data between main
and secondary storage.
 accesses raw disks or file system files and
provides a memory space divided into
segments, which are a linear collection of
equal-sized pages.
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Storage Layer: Logical Data Model
Logical Data Model: logical tree
 New nodes can be inserted as children
or siblings of existing nodes
 Any node can be removed
 Individual documents are represented
as ordered trees
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Mapping between XML and the
Logical Model
A small wrapper class is used to map the
XML model with its node types and
attributes to a simple tree model and vice
versa:
 Elements are mapped one to one to tree
nodes of Logical Data Model
 Atributes are mapped to child nodes of an
additional attribute container child node
 The name of referenced entities are
retained in special internal nodes
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XML page Interpreter Storage
Formater
 The logical data tree is partitioned
into subtrees
 Each sudtree is stored in a single
record of variable lenght
 Each record contains a pointer to
the record containing the parent
node and the document identifier
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XML page Interpreter Storage
Formater
 Subtrees of original XML document are
stored together in a single physical record
 clusters connected subtrees of the
document tree into large records and
represents intra-record references
differently from inter-record references
 The inner structure of the subtrees is
retained
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XML segment mapping for large
trees
Proxy nodes refer to connected subtrees not stored in
the same record
Helper aggregate nodes group together a subset of
children of a node
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Index Structures
Natix uses two Index Structures:
 Full text index framework
(inverted
files): store lists of document
Index
 eXtended Access Support Relation
references
to indicate
 Map
search
terms in
to which
list identifier and
List
Manager
 Preserves the parent/child, ancestor/
documents
search
terms
appear
store
these
mappings
persistenly

Maps
the
list
identifiers
to
the
actual
descandant,
and
preceding/following
FragmentedList

lists
(managing
the
directory
offor
the

Provides
the
main
interface
relationships
between
nodes
Lists
are
divided
to
fragments
that
fit the
on a
ContextDescription
inverted file)
page to
+combined
linked
+
can
be
traversed
user
work together
with
inverted
files
The XASR
with
a
full
text

Establishes the actual representation
sequentially
index
a powerful
in provides
which data
is storedmethod
in a list
It manages
all the fragments
of one list and
to search
on contentens
of nodes
control insertions and deletions on this list
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Natix Physical Algebra
‘Let’, ‘for’, ‘where’ and ‘return’ in
XQuery are supported
‘Select’, ‘map’, ‘join’, ‘grouping’ and
‘sort’ operations are performed by
standard algebraic operators
borrowed from relational context
‘D-join’ and ‘unary and binary
grouping’ are borrowed from the
object oriented context
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Natix Physical Algebra
Scan operations: e. g. ExpressionScan
ExpressionScan: generates a tuple containing
the root of the document identified by its
name by evaluating a given expression
UnnestMap is used to generate variable bindings
for XPath expressions
e.g./a//b/c  UnnestMap$4=child($3,c)(
UnnestMap$3=desc($2,b)(
UnnestMap$2=child($1,a)([$1])))
‘BA-Map’, ‘FL-Map’, ’Groupify-GroupApply’ and
‘NGroupify-NGroupApply’ are use to construct
the XML result
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Example Plans (1):
This query retrieves the
title and the year for all
recent books
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Example Plans (2):
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To do...
 Support for functions inside XPath
expressions
 Cannot import DTDs as of now
 Support for different character encodings
 Support for XML namespaces
preparing for the launch of the first
full commercial end-user release of
Natix that may support all these
features
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Questions ?
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References
Natix: A Technology Overview:
http://pi3.informatik.unimannheim.de/publications.html#79
Efficient storage of XML data:
http://pi3.informatik.unimannheim.de/publications.html#79
Anatomy of a Natix XML base Management
System:
http://pi3.informatik.unimannheim.de/publications.html#79
Alebraic XML Construction and its Optimization
in Natix:
http://pi3.informatik.unimannheim.de/publications.html#79
Data ex machina:
www.dataexmachina.de/natix.html
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Thank You
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