1. Object Modeling J. Stephen Schiavo Missouri Southern State University

2. Object Modeling Definition Concepts Objects, attributes, methods, encapsulation Classes, generalization, specialization Object/class relationship Messages Polymorphism Modeling process

3. Definition Object-Oriented Analysis & Design: The application of objects to understanding existing systems, and in specifying new or improved systems Object Modeling: Technique for identifying objects in the system and the relationships among them

4. Concepts Objects: Entities in the environment, capable of being seen, touched, sensed; and of experiencing events. Attributes: characteristics of objects Behavior(s): Things an object can do, or you can do to an object: methods Encapsulation: packaging attributes and methods together in the object.

5. Concepts … Classes: set of objects with common attributes and behaviors. Retail Stores, Students, Vehicles, … Generalization: gathering common aspects of similar classes to form a super-type Specialization: distinguishing one instance of a class by adding or modifying attributes or methods to create a subtype.

6. Classes / Sub & Super Classes Students: Maj, Advr, Hrs Faculty: Ten, TrmDeg Admin’r: Level, Vac Employee: Dep, Sal, Ins SSN, Name, Addr, Phone;

7. Concepts … Object/class relationships: Natural relationship among classes, just as in the entity-relationship data model Messages: How one object interacts with, i.e, how it calls or uses another object Polymorphism: Behaviors of the same name can differ markedly with objects. “Shut” is a different action for objects door, window, suitcase, drawer, faucet, mouth.

8. Modeling process Identifying objects Use case (‘yooss’ case)modeling – scenarios Use case: sequence of steps in a task Actor: anything interacting with system; a user or role; internal, or external Organizing objects and relationships Object Association Model What do these look like? (Figure 8.8) verb

9. Identifying objects 1.Identify actors (people, places, & things) and use cases (transactions) 2.Constructing the use case model diagram: Which actors involved in which cases 3.Documenting use case course of events a. Name the initiating actor b. Generally describe the transaction c. Step-by-step process through typical case d. Pre-and-post conditions (before and after case) e. Assumptions: performance, security, etc. Figure 8.9

10. Identifying objects … 4.Identifying use case dependencies showing which case must follow which 5.Document alternative course of events for non- typical situations: an order from a credit- impaired client; booking a flight for a disabled person or for a VIP ( or for a disabled VIP!) … 6.Finding potential objects, selecting objects: remove duplicates (synonyms), actors outside the system, non-unique actors, etc…

11. Organizing objects and relationships 1.Identify associations and multiplicity: what one object needs to know about or do to (or do with) another object 2.Identifying generalizations and specializations … subtypes/super-types … as in person  employee  manager 3.Identifying aggregation relationships (is part of …), e.g., Truck  cab & trailer 4.Preparing the object association model (Figure 8.16) What does this remind you of?