Pratt & Adamski chapter 9 & Some extra material The Object-Oriented approach Object-Oriented DBMSs Semantic Object Models Spring 2012
Jan 03, 2016
Pratt & Adamski chapter 9&
Some extra material
The Object-Oriented approachObject-Oriented DBMSsSemantic Object Models
Spring 2012
Overview
• Object-Oriented Systems
• Class Diagrams
• Unified Modeling Language (UML)
• Object-Oriented DBMS
• Semantic Object Models (SOM)
Object-Oriented Systems
• 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: • 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)
MessageObjects 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
A Customer object is customer data and customer methodsThe attributes of customer object are Name, Address, Account No, Balance DueThe methods on the customer object are Send-Invoice, Add-Customer, etc.
Customer
NameAddressAccount NoBalance Due
Add-Customer()Update-Customer()Get-Balance-Due()Send-Invoice()
Smith: Customer
-Smith-1109 Main St.-1100987546-$589.19
Add-Customer()Update-Customer()Get-Balance-Due()Send-Invoice()
Class Object
Unified Modeling Language (UML)
Unified Modeling Language (UML)Original version released in 1996Became 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
Manage Projects
Project Manager
Resource Manager
Use Case Diagram Class Diagram
Resource
Salaried Hourly
Sequence Diagram
Unified Modeling Language (UML)
1. Use Case Diagram2. Class Diagrams3. Object Diagrams4. Sequence Diagrams5. Collaboration Diagrams6. Statechart Diagrams7. Activity Diagrams8. Component Diagrams9. Deployment Diagrams
Unified Modeling Language (UML)
Use-cases
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 DiagramsDepiction of a system’s behavior or functionality under various conditions as the system responds to requests from users
Actor
Use-case
System boundary
Association (connection)
Include relationship
Extend relationship
Generalization relationship
StudentUseCase1
<<include>>
<<extend>>
Source: Dr. Sidorova, UNT
Example of a use case
diagram from
Wikepidea
Source: Dr. Sidorova, UNT
Class: Key Concepts
ClassA template or prototype that defines the composition and the behavior of all objects of certain kinds. These objects are called instances of the class
InheritanceA mechanism to organize classes by commonalities.
subclasses, specialization superclass, generalization Example:
Student GradStudent MSStudent PhDStudent UGStudent
Class diagrams
A class: point An object: p1
Attributes or fields: int x, y;
A method: point move(int dx, int dy)
A message: p2 = p1.move(10, 10)
Point
xy
Move
Fields (attributes)
Class name
methods
p1: Point
x = 0y = 0
p2: Point
x = 10y = 10
• Name of class
• Attributes
• Data types
• Methods (operations)
• Association (relationship)
• Multiplicity (cardinality)
Class Diagram details
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 ProductsFigure 9.24
Class Diagram with ConstraintsFigure 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
1. Complex Objects2. Object Identity3. Encapsulation4. Information Hiding5. Types (classes)6. Inheritance7. Late Binding (polymorphism)8. Computational Completeness9. Extensibility10. Persistence11. Performance12. Concurrent Update support13. Recovery support14. 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
1. * Semantic Object
2. * Object Identifier (primary key)
3. * Object Properties or Attributes
4. * Semantic Object Links
5. * 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.3Instance 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:– Simple Data Values (S)– Multi-Valued (MV or 1.N)– Composite or Group Attributes (G)– Object attributes or Semantic Object Links (SOLs);
• (see below)• 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.4Semantic 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
• Object-Oriented Systems
• Class Diagrams
• Unified Modeling Language (UML)
• Object-Oriented DBMS
• Semantic Object Models (SOM)