Lecture Systems Analysis and Design in a Changing World - Chapter 2: Approaches to System Development

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Learning objectives for chapter 2: Explain the purpose and various phases of the systems development life cycle (SDLC); explain the differences between a model, a tool, a technique, and a methodology; describe the two overall approaches used to develop information systems: the traditional method and the object-oriented method,...

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Nội dung Text: Lecture Systems Analysis and Design in a Changing World - Chapter 2: Approaches to System Development

2 2 Learning Objectives Chapter 2:  Explain the purpose and various phases of the Approaches to System systems development life cycle (SDLC) Development  Explain the differences between a model, a tool, Systems Analysis and Design in a Changing a technique, and a methodology World, 3rd Edition  Describe the two overall approaches used to develop information systems: the traditional method and the object-oriented method Systems Analysis and Design in a Changing World, 3rd Edition 2 2 2 Learning Objectives (continued) Overview  Describe some of the variations of the system  Systems development life cycle (SDLC) development life cycle (SDLC)  Provides overall framework for managing system development process  Describe the key features of current trends in  Two main approaches to SDLC system development: the spiral model, eXtreme  Traditional approach: structured systems Programming (XP), the Unified Process (UP), and development and information engineering Agile Modeling  Object-oriented approach: object technologies requires different approach to analysis, design, and programming  Explain how automated tools are used in system development  All projects use some variation of SDLC Systems Analysis and Design in a Changing World, 3rd Edition 3 Systems Analysis and Design in a Changing World, 3rd Edition 4 2 2 Phases of the Systems Development Systems Development Life Cycle (SDLC) Lifecycle (SDLC)  Systems development project  Project planning: initiate, ensure feasibility, plan  Planned undertaking with fixed beginning and end schedule, obtain approval for project  Produces desired result or product  Analysis: understand business needs and  Can be a large job of thousands of hours of effort processing requirements or a small one month project  Design: define solution system based on  Successful development project: requirements and analysis decisions  Provides a detailed plan to follow  Implementation: construction, testing, user  Organized, methodical sequence of tasks and training, and installation of new system activities  Produces reliable, robust, and efficient system  Support: keep system running and improve Systems Analysis and Design in a Changing World, 3rd Edition 5 Systems Analysis and Design in a Changing World, 3rd Edition 6
2 2 Information System Development Phases SDLC and problem-solving  Similar to problem-solving approach  Organization recognizes problem (Project Planning)  Project team investigates, understands problem and solution requirements (Analysis)  Solution is specified in detail (Design)  System that solves problem built and installed (Implementation)  System used, maintained, and enhanced to continue to provide intended benefits (Support) Systems Analysis and Design in a Changing World, 3rd Edition 7 Systems Analysis and Design in a Changing World, 3rd Edition 8 2 2 Planning Phase of SDLC Analysis Phase of SDLC  Define business problem and scope  Gather information to learn problem domain  Produce detailed project schedule  Define system requirements  Confirm project feasibility  Build prototypes for discovery of requirements  Economic, organizational, technical, resource, and schedule  Prioritize requirements  Staff the project (resource management)  Generate and evaluate alternatives  Launch project  official announcement  Review recommendations with management Systems Analysis and Design in a Changing World, 3rd Edition 9 Systems Analysis and Design in a Changing World, 3rd Edition 10 2 2 Design Phase of SDLC Implementation Phase of SDLC  Design and integrate the network  Construct software components  Design the application architecture  Verify and test  Design the user interfaces  Design the system interfaces  Convert data  Design and integrate the database  Train users and document the system  Prototype for design details  Install the system  Design and integrate system controls Systems Analysis and Design in a Changing World, 3rd Edition 11 Systems Analysis and Design in a Changing World, 3rd Edition 12
2 2 Support Phase of SDLC Scheduling Project Phases  Maintain system  Waterfall approach – each phase falls into next  Small patches, repairs, and updates phase  Freeze planning specifications before analysis  Enhance system  Freeze analysis specifications before design  Small upgrades or enhancements to expand system capabilities  Once go over the waterfall for each phase, do not go back  Larger enhancements may require separate development project  Overlapping (or concurrent) phases  Support users  Waterfall is not realistic, we are not perfect  Help desk and/or support team  Overlaps can be more efficient than waterfall Systems Analysis and Design in a Changing World, 3rd Edition 13 Systems Analysis and Design in a Changing World, 3rd Edition 14 2 2 Scheduling Project Phases (continued) The waterfall approach to the SDLC  Iteration - Work activities are repeated  Each iteration refines previous result  Approach assumes no one gets it right the first time  There are a series of mini projects for each iteration  Example: Outline, rough draft, edited result  Example: Blueprint, frame, completed house Systems Analysis and Design in a Changing World, 3rd Edition 15 Systems Analysis and Design in a Changing World, 3rd Edition 16 2 2 Overlap of Systems Development Iterations across life cycle phases Activities Systems Analysis and Design in a Changing World, 3rd Edition 17 Systems Analysis and Design in a Changing World, 3rd Edition 18
2 2 Some Models Used in System Methodologies and Models Development  Methodologies  Comprehensive guidelines to follow for completing every SDLC activity  Collection of models, tools, and techniques  Models  Representation of an important aspect of real world, but not same as real thing  Abstraction used to separate out aspect  Diagrams and charts  Project planning and budgeting aids Systems Analysis and Design in a Changing World, 3rd Edition 19 Systems Analysis and Design in a Changing World, 3rd Edition 20 2 2 Tools and Techniques Some Tools Used in System Development  Tools  Software support that helps create models or other required project components  Range from simple drawing programs to complex CASE tools  Techniques  Collection of guidelines that help analyst complete system development activity or task  Can be step-by-step instructions or just general advice Systems Analysis and Design in a Changing World, 3rd Edition 21 Systems Analysis and Design in a Changing World, 3rd Edition 22 2 2 Some Techniques Used in System Relationships Among Components of a Development Methodology Systems Analysis and Design in a Changing World, 3rd Edition 23 Systems Analysis and Design in a Changing World, 3rd Edition 24
2 2 Two Approaches to System Development Three Structured Programming Constructs  Traditional Approach  Also called structured system development  Structured analysis and design technique (SADT)  Structured programming  Improves computer program quality  Allows other programmers to easily read and modify code  Each program module has one beginning and one ending  Three programming constructs (sequence, decision, repetition) Systems Analysis and Design in a Changing World, 3rd Edition 25 Systems Analysis and Design in a Changing World, 3rd Edition 26 2 2 Top-Down Programming Top-Down or Modular Programming  Divides complex programs into hierarchy of modules  The module at top controls execution by “calling” lower level modules  Modular programming  Similar to top-down programming  One program calls other programs to work together as single system Systems Analysis and Design in a Changing World, 3rd Edition 27 Systems Analysis and Design in a Changing World, 3rd Edition 28 2 2 Structure Chart Created Using Structured Design Structured Design Technique  Technique developed to provide design guidelines  What set of programs should be  What program should accomplish  How programs should be organized into a hierarchy  Modules are shown with structure chart  Main principle of program modules  Loosely coupled – module is independent of other modules  Highly cohesive – module has one clear task Systems Analysis and Design in a Changing World, 3rd Edition 29 Systems Analysis and Design in a Changing World, 3rd Edition 30
2 2 Data Flow Diagram (DFD) created using Structured Analysis Structured Analysis Technique  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 31 Systems Analysis and Design in a Changing World, 3rd Edition 32 2 2 Entity-Relationship Diagram (ERD) created Structured Analysis Leads to Structured using the Structured Analysis technique Design and Structured Programming Systems Analysis and Design in a Changing World, 3rd Edition 33 Systems Analysis and Design in a Changing World, 3rd Edition 34 2 2 Information Engineering (IE) Object-Oriented Approach  Views information system as collection of  Refinement to structured development interacting objects that work together to accomplish tasks  Methodology with strategic planning, data modeling, automated tools focus  Objects - things in computer system that can respond to messages  More rigorous and complete than SADT  No processes, programs, data entities, or files are defined – just objects  Uses process dependency diagram  Object-oriented analysis (OOA)  Industry merged key concepts from structured  Defines types of objects that do work of system development and information engineering  Shows how objects interact with users to complete approaches into traditional approach tasks Systems Analysis and Design in a Changing World, 3rd Edition 35 Systems Analysis and Design in a Changing World, 3rd Edition 36
2 2 Object-Oriented Approach to Systems 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 37 Systems Analysis and Design in a Changing World, 3rd Edition 38 2 2 Class Diagram Created During OO SDLC Variations Analysis  Many variations of SDLC in practice  No matter which one, tasks are similar  Based on variation of names for phases  SDLC compared to IE compared to UP  Based on emphasis on people  User-centered design, participatory design  Based on speed of development  Rapid application development (RAD)  Prototyping Systems Analysis and Design in a Changing World, 3rd Edition 39 Systems Analysis and Design in a Changing World, 3rd Edition 40 2 2 Life Cycles with Different Names for Current Trends in Development Phases  Spiral Model  Highly iterative approach  Works around the phases (analysis, design, construction, testing, integration with previous prototype component) in a spiral until project is complete  Initial planning is to do just enough analysis to build initial prototype  Each iteration in the spiral addresses greatest risk Systems Analysis and Design in a Changing World, 3rd Edition 41 Systems Analysis and Design in a Changing World, 3rd Edition 42
2 2 The Spiral Life Cycle Model Extreme Programming (XP)  Recent, lightweight, development approach to keep process simple and efficient  Describes system support needed and required system functionality through informal user stories  Has users describe acceptance tests to demonstrate defined outcomes  Relies on continuous testing and integration, heavy user involvement, programming done by small teams Systems Analysis and Design in a Changing World, 3rd Edition 43 Systems Analysis and Design in a Changing World, 3rd Edition 44 2 2 The Unified Process (UP) The Unified Process (UP) (continued)  Object-oriented development approach  Reinforces six best practices  Offered by IBM / Rational  Develop iteratively  Booch, Rumbaugh, Jacobson  Define and manage system requirements  Unified Modeling Language (UML) used primarily for modeling  Use component architectures  UML can be used with any OO methodology  Create visual models  UP defines 4 life cycle phases  Verify quality  Inception, elaboration, construction, transition  Control changes Systems Analysis and Design in a Changing World, 3rd Edition 45 Systems Analysis and Design in a Changing World, 3rd Edition 46 2 2 Agile Modeling Agile Modeling (continued)  Hybrid of XP and UP (Scott Ambler) has more  Simplicity: models than XP, less documents than UP  Interactive and Incremental Modeling:  Use simple content  Apply right models  Depict models simply  Create several models in parallel  Use simplest modeling tools  Model in small increments  Teamwork:  Validation  Get active stakeholder participation  Consider testability  Encourage collective ownership  Model with others and display models publicly  Prove model is right with code Systems Analysis and Design in a Changing World, 3rd Edition 47 Systems Analysis and Design in a Changing World, 3rd Edition 48
2 2 CASE Tool Repository Contains all Tools to Support System Development System Information  Computer-Aided System Engineering (CASE)  Automated tools to improve the speed and quality of system development work  Contains database of information about system called repository  Upper CASE - support for analysis and design  Lower CASE - support for implementation  ICASE - integrated CASE tools Systems Analysis and Design in a Changing World, 3rd Edition 49 Systems Analysis and Design in a Changing World, 3rd Edition 50 2 2 Summary Summary (continued)  Systems development projects are organized  All development approaches use a SDLC to around the SDLC manage the project.  SDLC Phases include project planning, analysis,  Models, techniques, and tools make up a design, implementation, and support to be systems development methodology completed for each project  Systems developers learn SDLC based on the  System development methodologies are based sequential waterfall approach on traditional approach or object-oriented approach  In practice, phases overlap and projects contain many iterations of analysis, design, and  System development methodology provides implementation activities guidelines to complete every activity in the SDLC Systems Analysis and Design in a Changing World, 3rd Edition 51 Systems Analysis and Design in a Changing World, 3rd Edition 52 2 Summary (continued)  Original SDLC was waterfall approach  Most SDLC use iteration across phases  Rapid application development (RAD) goal is to speed up development  Current trends include: spiral model, eXtreme Programming (XP), Unified Process (UP) and Agile Modeling  CASE tools are designed to help analysts complete tasks Systems Analysis and Design in a Changing World, 3rd Edition 53