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Producing Production Quality Software

Producing Production Quality Software. Lecture 4: Object-Oriented Design Prof. Arthur P. Goldberg Fall, 2005. Design and Development Steps. Requirements gathering Specification Architecture (for bigger systems) Design Implementation Test. Object-Oriented (OO) Design. What’s an object?

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Producing Production Quality Software

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  1. Producing Production Quality Software Lecture 4: Object-Oriented Design Prof. Arthur P. Goldberg Fall, 2005

  2. Design and Development Steps • Requirements gathering • Specification • Architecture (for bigger systems) • Design • Implementation • Test

  3. Object-Oriented (OO) Design • What’s an object? • State (instance variables) and • Operations (methods that act on the state and other inputs). • What’s good about object orientation? • Abstraction • Encapsulation • Reusability

  4. Key Steps In OO Design (Given a specification and an architecture) • Within a module identify real or abstract entities • Map entities to objects (i.e., classes) • Then determine • Object state and operations • I.e., instance variables and methods • Object relationships • I.e., inheritance and composition • Tests

  5. Approaches for Identifying Classes • Noun phrase • Use-case driven • Classes, Responsibilities and Collaborators • Common Class Patterns

  6. Noun Phrase Technique • Enumerate Noun phrases • Eliminate irrelevant • Eliminate redundant • Identify attributes • Describe each class’s purpose Try this with the ViaNet Bank ATM

  7. Use-case Driven Approach • Identify classes through sequence and collaboration modeling • Develop sequence diagrams Try this with the ViaNet Bank ATM

  8. Classes, Responsibilities and Collaborators (CRC) An object’s collaborators are objects that cooperate with the object • Describe each class on an index card: • Iterate! • Keep collaborators physically nearby. • Combine similar classes in hierarchies Try this with the ViaNet Bank ATM

  9. Common Class Patterns • Concept class; e.g., [performance] • Events class; • Organization class • People class • Places class • Things and devices class Try this with the ViaNet Bank ATM

  10. OO Design Methodologies • Unified (Booch, Rumbaugh and Jacobson) approach • Use-case driven development • OO analysis = specification • OO design • Incremental development and prototyping • Continuous testing

  11. OO Design Axioms • The independence axiom. Maintain the independence of components. • The information axiom. Minimize the complexity (information content) of the design. • Design rules (antecedent axioms): • Design highly cohesive objects that require low coupling (1, 2). • Each class should have a single purpose (1, 2). • A large number of simpler classes enhances reusability (1, 2). • Map strongly from objects in the analysis to objects in the design (1). • Promote standardization by reusing classes and building to standard interfaces (2). • Design for inheritance—move common behavior to superclasses (2).

  12. References • Bahrami, Ali, Object-Oriented Systems Development, 1999. • Booch, Jacobson and Rumbaugh. The Unified Modeling Language, Notation Guide version 1.1. http://www.rational.com/uml/html/notation (9/97) • Booch. Object-Oriented Design with Applications, Benjamin-Cummings. 1994. • Coad and Yourdon. Object-Oriented Design, 1991. • Rumbaugh, Blaha, Permerlani, et. al., Object-Oriented Modeling and Design, 1991. • Coad and Yourdon. Object-Oriented Analysis, 1991. • Jacobson, Object-Oriented Software Engineering: A Use Case Driven Approach, 1994. • Beck, Cunningham, A Laboratory For Teaching OO Thinking, OOPSLA, 1989 (CRC technique)

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