System Development u Systems l l development life

System Development u Systems l l development life cycle (SDLC) Provides overall framework for managing system development process u Two l Overview 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 u All projects use some variation of SDLC

System Development u u SDLC Systems development project l Planned undertaking with fixed beginning and end l Produces desired result or product l Can be a large job of thousands of hours of effort or a small one month project Successful development project: l Provides a detailed plan to follow l Organized, methodical sequence of tasks and activities l Produces reliable, robust, and efficient system

System Development SDLC Phases of the Systems Development Lifecycle (SDLC) u Project planning: initiate, ensure feasibility, plan schedule, u Analysis: understand business needs and processing u Design: define solution system based on requirements and u Implementation: construction, testing, user training, and u Support: keep system running and improve obtain approval for project requirements analysis decisions installation of new system

System Development SDLC Information System Development Phases

System Development SDLC and problem-solving u Similar to problem-solving approach l l l 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)

System Development SDLC Planning Phase of SDLC u Define business problem and scope u Produce detailed project schedule u Confirm project feasibility l Economic, organizational, technical, resource, and schedule u Staff the project (resource management) u Launch project official announcement

System Development SDLC Analysis Phase of SDLC problem domain u Gather information to learn u Define system requirements u Build prototypes for discovery of requirements u Prioritize requirements u Generate and evaluate alternatives u Review recommendations with management

System Development Design Phase of SDLC u Design and integrate the network u Design the user interfaces u Design the system interfaces u Design and integrate the database u Prototype for design details u Design and integrate system controls application architecture SDLC

System Development Implementation Phase of SDLC u Construct software components u Verify and test u Convert data u Train users and document the system u Install the system SDLC

System Development SDLC Support Phase of SDLC u Maintain system l u u Small patches, repairs, and updates Enhance system l Small upgrades or enhancements to expand system capabilities l Larger enhancements may require separate development project Support users l Help desk and/or support team

System Development u u u Scheduling Project Waterfall approach – each phase falls into next phase l Freeze planning specifications before analysis l Freeze analysis specifications before design l Once go over the waterfall for each phase, do not go back Overlapping (or concurrent) phases l Waterfall is not realistic, we are not perfect l Overlaps can be more efficient than waterfall Iteration - Work activities are repeated l Each iteration refines previous result l Approach assumes no one gets it right the first time l There a series of mini projects for each iteration u Example: Outline, rough draft, edited result u Example: Blueprint, frame, completed house

System Development SDLC The waterfall approach to the SDLC

System Development Overlap of Systems Development Activities

System Development Iterations across life cycle phases

System Development Methodologies and Models u Methodologies l Comprehensive guidelines to follow for completing every SDLC activity l Collection of models, tools, and techniques u Models l Representation of an important aspect of real world, but not same as real thing l Abstraction used to separate out aspect l Diagrams and charts l Project planning and budgeting aids

System Development Some Models Used in System Development

System Development u Tools l l u Tools and Techniques Software support that helps create models or other required project components Range from simple drawing programs to complex CASE tools Techniques l l Collection of guidelines that help analyst complete system development activity or task Can be step-by-step instructions or just general advice Some Tools Used in System Development

System Development Some Techniques Used in System Development

System Development Relationships Among Components of a Methodology

System Development Two Approaches to System Development u Traditional Approach l Also called structured system development l Structured analysis and design technique (SADT) u Structured programming l Improves computer program quality l Allows other programmers to easily read and modify code l Each program module has one beginning and one ending l Three programming constructs (sequence, decision, repetition)

System Development Three Structured Programming Constructs

System Development Top-Down Programming u Divides complex programs into hierarchy of modules u The module at top controls execution by “calling” lower level modules u Modular programming l u Similar to top-down programming One program calls other programs to work together as single system

System Development Top-Down or Modular Programming

System Development u Technique guidelines Structured Design developed to provide design l What set of programs should be l What program should accomplish l How programs should be organized into a hierarchy u Modules u Main are shown with structure chart principle of program modules l Loosely coupled – module is independent of other modules l Highly cohesive – module has one clear task

System Development Structure Chart Created Using Structured Design Technique

System Development Structured Analysis u Define what system needs to do (processing requirements) u Define data system needs to store and use (data requirements) u Define inputs and outputs u Define how functions work together to accomplish tasks u Data flow diagrams and entity relationship diagrams show results of structured analysis

System Development Data Flow Diagram (DFD) created using Structured Analysis Technique

System Development Entity-Relationship Diagram (ERD) created using the Structured Analysis technique

System Development Structured Analysis Leads to Structured Design and Structured Programming

System Development u Refinement Information Engineering to structured development u Methodology with strategic planning, data modeling, automated tools focus u More rigorous and complete than SADT u Uses process dependency diagram u Industry merged key concepts from structured development and information engineering approaches into traditional approach

System Development Object-Oriented Approach u Views information system as collection of interacting objects that work together to accomplish tasks l Objects - things in computer system that can respond to messages l No processes, programs, data entities, or files are defined – just objects u Object-oriented analysis (OOA) l Defines types of objects that do work of system l Shows how objects interact with users to complete tasks

System Development Object-Oriented Approach to Systems Object-Oriented Approach

System Development u Object-oriented Object-Oriented Approach design (OOD) l Defines object types needed to communicate with people and devices in system l Shows how objects interact to complete tasks l Refines each type of object for implementation with specific language of environment u Object-oriented l programming (OOP) Writing statements in programming language to define what each type of object does u Benefits of OOA include naturalness and reuse

System Development Class Diagram Created During OO Analysis

System Development u Many l variations of SDLC in practice No matter which one, tasks are similar u Based l on variation of names for phases SDLC compared to IE compared to UP u Based l SDLC Variations on emphasis on people User-centered design, participatory design u Based on speed of development l Rapid application development (RAD) l Prototyping

System Development Life Cycles with Different Names for Phases

System Development Current Trends in Development u Spiral Model l Highly iterative approach l Works around the phases (analysis, design, construction, testing, integration with previous prototype component) in a spiral until project is complete l Initial planning is to do just enough analysis to build initial prototype l Each iteration in the spiral addresses greatest risk

System Development The Spiral Life Cycle Model

System Development u u Extreme Programming 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

System Development u Object-oriented development approach u Offered by IBM / Rational l Unified Process Booch, Rumbaugh, Jacobson u Unified Modeling Language (UML) used primarily for modeling u UML can be used with any OO methodology u UP defines 4 life cycle phases l u Inception, elaboration, construction, transition Reinforces six best practices l Develop iteratively l Define and manage system requirements l Use component architectures l Create visual models l Verify quality l Control changes

System Development u u u Agile Modeling Hybrid of XP and UP (Scott Ambler) has more models than XP, less documents than UP Interactive and Incremental Modeling: l Apply right models l Create several models in parallel l Model in small increments Teamwork: l Get active stakeholder participation l Encourage collective ownership l Model with others and display models publicly Simplicity: l Use simple content l Depict models simply l Use simplest modeling tools Validation l Consider testability l Prove model is right with code

System Development Tools to Support System Development u Computer-Aided System Engineering (CASE) l l Automated tools to improve the speed and quality of system development work Contains database of information about system called repository u Upper CASE - support for analysis and design u Lower CASE - support for implementation u ICASE - integrated CASE tools

System Development CASE Tool Repository Contains all System Information

System Development u u Summary Systems development projects are organized around the SDLC Phases include project planning, analysis, design, implementation, and support to be completed for each project Systems developers learn SDLC based on the sequential waterfall approach In practice, phases overlap and projects contain many iterations of analysis, design, and implementation activities u All development approaches use a SDLC to manage the project. u Models, techniques, and tools make up a systems development methodology u u System development methodologies are based on traditional approach or object-oriented approach System development methodology provides guidelines to complete every activity in the SDLC u Original SDLC was waterfall approach u Most SDLC use iteration across phases u Rapid application development (RAD) goal is to speed up development u u Current trends include: spiral model, e. Xtreme Programming (XP), Unified Process (UP) and Agile Modeling CASE tools are designed to help analysts complete tasks