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Outline

Outline. Object-Oriented Concepts Modeling Components Structured Method Evaluation Procedure Object-Oriented Methods Structured Methods Review of Object Orientedness of System Development Methods Conclusions. Object-Oriented Concepts.

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Outline

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  1. Outline • Object-Oriented Concepts • Modeling Components • Structured Method Evaluation Procedure • Object-Oriented Methods • Structured Methods • Review of Object Orientedness of System Development Methods • Conclusions

  2. Object-Oriented Concepts • Three principles that make OOD to improve software design for reliability and maintenance. • Abstraction: Objects are an abstraction of parts of real-world. More maintainable and reusable. • Encapsulation: Objects hide their internal contents from other components to improve maintainability. • Inheritance: By organizing objects in class hierarchies to promote reuse.

  3. Modeling Components • Objects vs. Traditional Concepts of Entities and Functions • Objects are close to entity concept. I.e. a collection of attributes, objects add activities to entity. • Objects are a type with one or more instances of type, same as entity-type concept • Objects instances may be changed by events and record state changes

  4. Structured Method Evaluation Procedure • Conceptual modeling: • The data and processing control parts of a system are modeled in one unit rather than separately; • The method produces model of objects communicating by messages; • Models object types and instances; • Classification of objects is supported with property inheritance.

  5. Procedure and guidance • The method should guide the analyst towards identifying and describing objects. • Guidance should be available for analysis, specification and design phases. • Transformations and products • Design transformation should support change of OO specifications into designs implementable in OOP languages.

  6. Object-Oriented Methods • Hierarchical Object-Oriented Design (HOOD) • The top-down hierarchical decomposition approach. HOOD is heavily geared towards an implementation in Ada. • The main process in HOOD is called the Basic Design Step. "A Basic Design Step has as its goal the identification of child objects of a given parent object, and of their individual relationships to other existing objects, or the refinement of a terminal object to the level of the code. • Object-Oriented System Design (OOSD) • Object-Oriented Systems Analysis (OOSA) • Object-Oriented Analysis (OOA) • ObjectOry

  7. R-A-S-D-I: Requirements, Analysis, Specification, Design and Implementations Feature analysis of Object-Oriented methods

  8. Structured Methods • Structure System Analysis and Design Method (SSADM) • Standard structured method used for UK government projects • Data-driven, 6 stages: • Analysis system operation and current problems • Specification of requirements • Selection of technical options • Logical data design • Logical process design • Physical design

  9. Information Engineering (IE) • Encourage data modeling • Functional specification uses process dependency and action diagram, separated from data modeling • Information System Activity and Change Analysis (ISAC) • Structure Analysis/Structured Design (SASD) • Structured Analysis and Design Technique (SADT) • Jackson System Development (JSD) • Nijssen’s Information Analysis Method (NIAM) • Mascot-3

  10. IS: Information System, RT: real-time Summary of method specification models and approaches

  11. Review of Object Orientedness of System Development Methods

  12. Conclusions • Use of a particular system development method will bias implementation of OO systems, OO design may not derived from any specification. • Data model and OO specification show considerable convergence. It is feasible to migrate from structured method such as JSD, IE and SSADM to OO Method. • Functionally based development methods are less well suited to development of OO system. • OO methods have yet proven in practice, they have little CASE tool support, lack of modeling techniques for reuse system development.

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