Methodology Review Chapter 7 Part 2: Design Methodology Object-Oriented Modeling and Design Byung-Hyun Ha

Lecture Outline  Introduction  OMT as S/W Engineering Methodology  OMT Methodology  Impact of an Object-Oriented Approach

Introduction  In Part 1, modeling concepts  OMT concepts, for object, dynamic, and functional models  What constitutes a model  In Part 2, design methodology  Process for devising the three OMT models  How to formulation a model  Language-independent methodology, applied equally well to object-oriented languages, traditional procedural language, and databases  In Part 3, implementation  How this generic design maps to specific implementation targets

OMT as S/W Engineering Methodology  Software engineering methodology  A process for the organized production of software, using a collection of predefined techniques and notational conventions  Presented as a series of steps with techniques (presented in Part 1) associated with each step  The steps are usually organized into a lifecycle consisting of several phases of development  Span of complete software lifecycle  Initial formulation of the problem  Analysis of requirement, design, implementation, and testing of the software  Operational phase during which maintenance and enhancement are performed

OMT as S/W Engineering Methodology  Two approaches to software development  Rapid prototyping approaching A small portion of the software is initially developed and evaluated through use The software is gradually made robust through incremental improvement to the specification, design, and implementation  Lifecycle approach Software is fully specified, fully designed, then fully implemented  OMT methodology applies equally well in either case

OMT Methodology  Phases  Analysis, system design, and object design  Analysis phase  Concerned with understanding and modeling the application and the domain within which it operates  Initial input: a problem statement which describes the problem to be solved and provides a conceptual overview of the proposed system  Output: a formal model that captures the three essential aspects of the system

OMT Methodology (cont’)  System design phase  Overall architecture of the system is determined  The system is organized into subsystems  Priorities are established for making design tradeoffs  Object design phase  The analysis model are elaborated, refined and then optimized to produce a practical design  There is a shift in emphasis from application concepts toward computer concepts  Determining efficient algorithms, optimized structure of object model, etc.

Impact of an Object-Oriented Approach  Shifting of development effort into analysis  Resulting design is cleaner and more adaptable  Future changes are much easier  Emphasis on data structure before function  A more stable bases are given to development process  Seamless development process  Refining the model developed in analysis phase progressively during throughout the development cycle  Interactive rather than sequential  Less chance of introducing inconsistencies and errors