1. CSC 480 Software Engineering OOAD Process

2. Topics Overview: OOAD Process The object model Identifying classes Responsibilities and collaborations Hierarchy: inheritance and aggregation

3. Macro Development Process The process can be roughly divided into three major phases Analysis: focusing on what are required Design: answering the questions of how to fulfill the requirements  Resulting in blueprints that map functional needs to program units (interrelated classes) Implementation: realizing the design with a working system

4. Down to the Ground-Level Ideas Needs statement Functional spec (D-req’ts) Design docs System in production System under dev. Prototypes High-up in the air Solid ground Analysis Design Implementation Conceptualization C-req’ts

5. Analysis Phase Specify system needs in a conceptual model  High-level, with details omitted  Document: system requirement specification (SRS) Completeness  a contract between client and developers Consistency : without contradiction Readability : customer & developer (C-&D-) req’ts Addressing all shareholders interests Testability : can be tested against reality

6. Requirements Engineering There is no clear-cut boundary between phases In OOA process, use cases are a powerful means to present and organize requirements  RUP claims to be use-case-driven  Good for revealing both external and internal needs (user and system requirements)  Can be used for design, implementation, testing, and user training purposes

7. The Design Phase The goal is to find and present a solution  The key is decomposition Interrelated classes: class  responsibilities  collaborations Focusing on architecture (key classes + interfaces), omitting implementation details The outcome is system design document (SDD)  Class diagrams  Sequence diagrams  State diagrams

8. Design Phase Also known as high-level design  Classes at various levels of abstraction  Relationships among classes Dependency Inheritance aggregation Product design or UI design may be needed  Story-boarding  Screen navigation charts

9. Implementation Phase Better known as the construction phase  Detail design: sub-class level Data structures, algorithms  Coding  Unit testing  Gradual integration and repeated “system” testing  Deployment

10. Object and Class An object is characterized by its  State:  Behavior:  Identity A class specifies objects with the same behavior An instance of a class is an object that belongs to the given class

11. Micro Development Process Largely driven by the stream of scenarios and architectural products  Identifying classes and objects  Identifying semantics of classes and objects  Identifying the relationships among classes and objects  Implementing classes and objects

12. Identifying Classes A rule of thumb is to look for nouns in SRS  Class candidates usually fall in following categories Tangible things Agents Events and transactions Users and roles Systems System interfaces and devices Foundational classes

13. Identifying Responsibilities Responsibilities can be mapped to a functional requirement Responsibilities include  Things an object need to know: state  Operations an object can perform: behavior Assign a responsibility to exactly one class Assign responsibilities as evenly among classes as possible

14. Identifying Relationships Relationship types  Hierarchical Inheritance Aggregation  Association Dependency: aka collaborations

15. Object Collaborations An object tends to fulfill its responsibilities by collaborating with other objects Client-server contract  Client: the object receiving a service  Server: the object providing the service  Contract: the interface definition through which a service may be requested  The client and server roles may change in different collaborations