IntroductiontoSoftwareEngineering(CEN-4010).ppt

Introduction to Software Engineering (CEN-4010) Spring 2006 Instructor: Masoud Sadjadi /~sadjadi/ Acknowledgements Dr. Bernd Bruegge Dr. Allen Dutoit Agenda Motivation System Design Overview Design Goals System Decomposition Summary Motivation “There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies.” - C.A.R. Hoare Why is Design so Difficult? Analysis: Focuses on the application domain Design: Focuses on the solution domain Design knowledge is a moving target The reasons for design decisions are changing very rapidly Halftime knowledge in software engineering: About 3-5 years What I teach today will be out of date in 3 years Cost of hardware rapidly sinking “Design window”: Time in which design decisions have to be made Technique Time-boxed prototyping The Purpose of System Design Bridging the gap between desired and existing system in a manageable way Use Divide and Conquer We model the new system to be developed as a set of subsystems Agenda Motivation System Design Overview Design Goals System Decomposition Summary System Design Overview System Design I (this lecture) 0. Overview of System Design 1. Design Goals 2. Subsystem Decomposition System Design II: Addressing Design Goals (next lecture) 3. Concurrency 4. Hardware/Software Mapping 5. Persistent Data Management 6. Global Resource Handling and Access Control 7. Software Control 8. Boundary Conditions Requirements Analysis ? System Design Nonfunctional requirements = Activity 1: Design Goals Definition Functional model = Activity 2: System decomposition (Selection of subsystems based on functional requirements, cohesion, and coupling) Object model = Activity 4: Hardware/software mapping Activity 5: Persistent data management Dynamic model = Activity 3: Concurrency Activity 6: Global resource handling Activity 7: Software control Subsy