Transcript Pratt & Adamski chapter 9 & Some extra material The Object-Oriented approach

Pratt & Adamski chapter 9
&
Some extra material
The Object-Oriented approach
Object-Oriented DBMSs
Semantic Object Models
Spring 2012
Overview
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Object-Oriented Systems
Class Diagrams
Unified Modeling Language (UML)
Object-Oriented DBMS
Semantic Object Models (SOM)
Object-Oriented Systems
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View the world in terms of objects ("things")
Easier to think of systems as objects (customer,
shipping clerk,,)
• main driver: reusability
Object-orientation appears as:
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Object-oriented user interfaces (90% of new projects)
Object-oriented programming (80% of new projects)
Object-oriented databases (5% or less)
OO analysis and design (30 to 40%)
Objects: Key Concepts
Definition: Objects are data guarded by a protective layer
of code. OO Software components consist of
variables and methods
Key concepts of the object-oriented paradigm:
• object
• attributes of objects
• methods of object show behavior (what it can
provide )
• class : template of objects
• inheritance (lower level objects can inherit from
higher level)
Objects: Key Concepts
Key Concepts (continued):
-Modularity (reduce complex systems into highly
cohesive but loosely coupled modules)
-Encapsulation (Information hiding in implementation)
Message
Objects communicate via message passing. A message
consists of an object (the recipient), a method, and
optional parameters.
Object Examples
Example: items in a department store.
TV is an object.
The attributes of this object are model, year, cost,
etc.The methods, for store are, purchase, repair
Radio is another object, so is a dishwasher
• many of these objects have similar properties
(attributes, methods)
• can define a hierarchy .
Object Examples
Customer
Smith: Customer
Name
Address
Account No
Balance Due
-Smith
-1109 Main St.
-1100987546
-$589.19
Add-Customer()
Update-Customer()
Get-Balance-Due()
Send-Invoice()
Add-Customer()
Update-Customer()
Get-Balance-Due()
Send-Invoice()
Class
Object
A Customer object is customer data and customer methods
The attributes of customer object are Name, Address, Account No, Balance Due
The methods on the customer object are Send-Invoice, Add-Customer, etc.
Unified Modeling Language
(UML)
Unified Modeling Language (UML)
Original version released in 1996
Became an International Standard in 1997 with the
formation of UML Partners (HP, IBM, Microsoft,
Oracle, Rational Software)
A graphical language for Object-Oriented Analysis
and Design (OOAD)
Manage
Resources
Resource
Manager
Resource
Project
Manager
Manage
Projects
Salaried
Use Case Diagram
Class Diagram
Hourly
Sequence Diagram
Unified Modeling Language
(UML)
Unified Modeling Language (UML)
1. Use Case Diagram
2. Class Diagrams
3. Object Diagrams
4. Sequence Diagrams
5. Collaboration Diagrams
6. Statechart Diagrams
7. Activity Diagrams
8. Component Diagrams
9. Deployment Diagrams
Use-cases
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Use cases describe the functionality of the system from the user
point of view.
Each use case provides one or more scenarios of how the system
should interact with the users called actors
Use cases are written in non-technical language, understood by
users
Use cases are written as a part of requirement analysis.
Use cases are separate and distinct from use case diagrams, which
allow one to abstractly work with groups of use cases.
Use case diagrams are created after the use case descriptions are
written.
Source: Dr. Sidorova, UNT
Use Cases Diagrams
Depiction of a system’s behavior or functionality under
various conditions as the system responds to requests from
users
Actor
Student
Use-case
UseCase1
System boundary
Association
(connection)
Include relationship
<<include>>
Extend relationship
<<extend>>
Generalization
relationship
Source: Dr. Sidorova, UNT
Example of
a use case
diagram
from
Wikepidea
Source: Dr. Sidorova, UNT
Class: Key Concepts
Class
A template or prototype that defines the composition
and the behavior of all objects of certain kinds.
These objects are called instances of the class
Inheritance
A mechanism to organize classes by commonalities.
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subclasses, specialization
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superclass, generalization
Example:
Student
GradStudent
MSStudent
PhDStudent
UGStudent
Class diagrams
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A class: point
An object: p1
 Attributes or fields:
int x, y;
Point
Class name
x
y
Fields
(attributes)
Move
methods
 A method:
point move(int dx, int dy)
 A message:
p2 = p1.move(10, 10)
p1: Point
p2: Point
x=0
y=0
x = 10
y = 10
Class Diagram details
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Name of class
Attributes
Data types
Methods (operations)
Association (relationship)
Multiplicity (cardinality)
Class Diagram details
• Associations are shown as lines joining classes
and represent relationships. Multiplicity
indicates the number of objects at the end of the
relationship. Example: 1..1, 0..n, 1..n.
• The visibility symbol indicates whether other
classes can view or update attribute values:
– Public visibility (+), any other class can view/update
– Protected visibility (#), class itself or its subclasses
can view/update
– Private visibility (-), only class itself can view/update
Class Diagram for Premiere Products
Figure 9.24
Class Diagram with Constraints
Figure 9.25
Class Diagram with a
Generalization and a Constraint
Figure 9.26
Object-Oriented DBMS (OODBMS)
• System in which data and the methods
operating on that data are encapsulated
into objects
• Store graphics, drawings, video, sound,
and other complex objects called binary
large objects (BLOBs)
• General concepts
– Objects and classes
– Methods and messages
– Inheritance
Rules for OODBMSs: what they
should support
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Complex Objects
Object Identity
Encapsulation
Information Hiding
Types (classes)
Inheritance
Late Binding (polymorphism)
Computational Completeness
Extensibility
Persistence
Performance
Concurrent Update support
Recovery support
Query facilities
Semantic Object Model (SOM):
a different approach
S-O MODEL
CHARACTERISTICS
• S-O Model More Bottom-Up-Oriented
than the E-R Model
• Both Are a Type of "Pseudo-Code“ or
"Flowchart" Tool For DB Design
• David Kroenke primary developer of the
SO Model (1994).
– The Model Is Robust But Lacks Standards.
– NOT Widely Used Yet in CASE Tools.
S-O MODEL DEFINITIONS
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* Semantic Object
* Object Identifier (primary key)
* Object Properties or Attributes
* Semantic Object Links
* Formulas
S-O MODEL DEFINITIONS
• * Semantic Objects -- Represented by a
Rectangle (See Fig B.2.a)
– A named collection of Properties that
sufficiently describes a distinct entity
(Things, Objects (Nouns) Of Importance To
The Users' Data Model)
– E.g., Employee, Customer, Inventory, Order,
Etc.
• Instance Of A Semantic Object (Fig B.3)
– Professor “Nick Evangelopoulos”
• Semantic Object Classes -– Collections Of Same Types Of Objects
Object Diagram Fig. B.2
Figure B.3
Instance of a Semantic Object
S-O MODEL DEFINITIONS
• * Semantic Objects are Distinct Entities -– There are NO “weak” semantic objects!
– Consider the relational DB design of an
ordering system: Line_Item would be property
of ORDER, not a distinct entity.
– Semantic Objects are ALWAYS independent!!
– Names in CAPITAL letters
• Semantic Objects:
• Must Exist In The Minds Of The Users-• This is Why They Are Called Semantic Objects
S-O MODEL DEFINITIONS
• Object Identifier:
– Identifies A Unique Object Instance (Key)
– May Be a Group or Composite
(concatenated) Key (OrderNum, LineNum),
(Cust_Name, Cust_Addr)
– ID NameMixedCase
– ID UniqueId when underlined
S-O MODEL DEFINITIONS
• * Properties (Or Attributes) -- Fig B.2
Characteristics Of Semantic Objects:
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Simple Data Values (S)
Multi-Valued (MV or 1.N)
Composite or Group Attributes (G)
Object attributes or Semantic Object Links (SOLs);
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• Paired attributes: If an object contains another object, the
second object will contain the first [SOLs are reciprocal]
– USE Mixed Case for Naming Convention: DeptId
Figure B.2 (b)
Cardinalities (Min.Max)
S-O MODEL DEFINITIONS
• * Semantic Object Link (SOL)
– Special Type of Property
– Recursiveness
– Represented by a rectangle inside of the SO
• * Formulas (F)
– Formula Functions: SUM, COUNT, MIN,
MAX, AVG
– Formula Expressions: e.g., Salary / 12
Figure B.2 (a) & (b) SOLs
S-O MODEL DEFINITIONS
(Misc..)
• Property Domains
– Set Of All Possible Values Of A Property
• Semantic Object Views (Fig. B.4)
– Subset Of Properties Of S-O Required By A
Particular Application Or User. Synthesis Of
Multiple Objects
– Views Required To Build Complete Object
Diagram.
Figure B.4
Semantic Object View
S-O DIAGRAMS Guidelines
• Picture Of User’s Defined Objects
– Non-Standard notation
• Rectangles for Objects; NAMES in Capital
letters inside rectangle
• Object Properties written in MixedCase
• SOLinks -- Written in Capital letters inside
their own rectangles within the SO
• Groups (Composites) properties are
bracketed or braced on Right-hand side
S-O DIAGRAMS Guidelines
(continued)
• Multi-valued property Cardinalities are
shown as Subscripts:
– 1.1, 1.N, 0.1, 0.N, etc. (also, MV)
– Actually Minimum and Maximum Cardinality
for each property (ID, S, G, or SOL)
• Min.Max The minimum and maximum allowable
occurrences for each property.
• 0.1 means that the property may have no
instances, but at most 1.
• 1.N means that the property must have at least
one instance, and could have many instances.
Figure B.2 (b)
Cardinalities (Min.Max)
Summary
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Object-Oriented Systems
Class Diagrams
Unified Modeling Language (UML)
Object-Oriented DBMS
Semantic Object Models (SOM)