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Approaches to Requierements Engineering

Approaches to Requierements Engineering. Reference: Systems Analysis and Design in a Changing World, 3 rd Edition, chapter 2 and chapter 6. Overview. Systems development life cycle (SDLC) Provides overall framework for managing system development process Two main approaches to SDLC

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Approaches to Requierements Engineering

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  1. Approaches to Requierements Engineering Reference: Systems Analysis and Design in a Changing World, 3rd Edition, chapter 2 and chapter 6

  2. Overview • Systems development life cycle (SDLC) • Provides overall framework for managing system development process • Two main approaches to SDLC • Traditional approach: structured systems development and information engineering • Object-oriented approach: object technologies requires different approach to analysis, design, and programming • All projects use some variation of SDLC Systems Analysis and Design in a Changing World, 3rd Edition

  3. Traditional and Object-Oriented Views of Activities Systems Analysis and Design in a Changing World, 3rd Edition

  4. Requirements Models for the Traditional and OO Approaches Systems Analysis and Design in a Changing World, 3rd Edition

  5. Structured Analysis • Define what system needs to do (processing requirements) • Define data system needs to store and use (data requirements) • Define inputs and outputs • Define how functions work together to accomplish tasks • Data flow diagrams and entity relationship diagrams show results of structured analysis Systems Analysis and Design in a Changing World, 3rd Edition

  6. Context Diagrams • DFD that summarizes all processing activity • Highest level (most abstract) view of system • Shows system boundaries • System scope is represented by a single process, external agents, and all data flows into and out of the system Systems Analysis and Design in a Changing World, 3rd Edition

  7. Context Diagram for RMO Order-Entry Subsystem Systems Analysis and Design in a Changing World, 3rd Edition

  8. Data Flow Diagrams • Graphical system model that shows all main requirements for an IS in one diagram • Inputs / outputs • Processes • Data storage • Easy to read and understand with minimal training Systems Analysis and Design in a Changing World, 3rd Edition

  9. DFD Fragment from the RMO Case Systems Analysis and Design in a Changing World, 3rd Edition

  10. Data Flow Diagram (DFD) created using Structured Analysis Technique Systems Analysis and Design in a Changing World, 3rd Edition

  11. Data Flow Diagram Symbols Systems Analysis and Design in a Changing World, 3rd Edition

  12. Entity-Relationship Diagram (ERD) created using the Structured Analysis technique Systems Analysis and Design in a Changing World, 3rd Edition

  13. Structured Analysis Leads to Structured Design and Structured Programming Systems Analysis and Design in a Changing World, 3rd Edition

  14. Object-Oriented Approach • Views information system as collection of interacting objects that work together to accomplish tasks • Objects - things in computer system that can respond to messages • No processes, programs, data entities, or files are defined – just objects • Object-oriented analysis (OOA) • Defines types of objects that do work of system • Shows how objects interact with users to complete tasks Systems Analysis and Design in a Changing World, 3rd Edition

  15. Object-Oriented Approach to Systems Systems Analysis and Design in a Changing World, 3rd Edition

  16. Object-Oriented Approach (continued) • Object-oriented design (OOD) • Defines object types needed to communicate with people and devices in system • Shows how objects interact to complete tasks • Refines each type of object for implementation with specific language of environment • Object-oriented programming (OOP) • Writing statements in programming language to define what each type of object does • Benefits of OOA include naturalness and reuse Systems Analysis and Design in a Changing World, 3rd Edition

  17. Class Diagram Created During OO Analysis Systems Analysis and Design in a Changing World, 3rd Edition

  18. Summary (continued) • System development methodologies are based on traditional approach or object-oriented approach • System development methodology provides guidelines to complete every activity in the SDLC Systems Analysis and Design in a Changing World, 3rd Edition

  19. Summary • Data flow diagrams (DFDs) used in combination with event table and entity-relationship diagram (ERD) to model system requirements IN TRADITIONAL APPROACH TO REQUIREMENS • DFDs model system as set of processes, data flows, external agents, and data stores • DFDs easy to read - graphically represent key features of system using small set of symbols • Many types of DFDs: context diagrams, DFD fragments, subsystem DFDs, event-partitioned DFDs, and process decomposition DFDs Systems Analysis and Design in a Changing World, 3rd Edition

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