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INTRODUCTION Chapter 1. Alan Dennis, Barbara Wixom, and David Tegarden John Wiley & Sons, Inc. Slides by Fred Niederman Edited by Solomon Negash. What are systems?.
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INTRODUCTIONChapter 1 Alan Dennis, Barbara Wixom, and David Tegarden John Wiley & Sons, Inc. Slides by Fred Niederman Edited by Solomon Negash
What are systems? A surgeon, a civil engineer and a software engineer were chatting at a bar. The discussion rolled around to whose profession was the oldest. The surgeon said that surgery was, since in the book of Genesis, God created Eve from one of Adam's ribs, and surely that involved surgery. The civil engineer countered by saying that before God created people, God created the heavens and the Earth from chaos, surely a feat of civil engineering. The software engineer just smiled and said “_________________________________?” • Downloaded from http://www.cis.gsu.edu/~shong/oojokes/ Jan 7, 2003
System Analysis and Design(Definition) • The study of a ___________ prior to taking some __________ (DeMarco, 1978) • The ___________ of establishing the services that the _________requires from a system and the ___________under which it operates and is developed (Summerville, 1995) • A __________used to develop computer-based ______________________ (Hoffer, George, & Valachich, 1999)
System Development Life Cycle (SDLC) • Planning • Why build the system? • Analysis • Who are the users? • What are the requirements? • What is the scope? • Design • How will the system work? • Implementation • System delivery • How do we support the users?
Major Attributes of the Lifecycle • The project • Moves systematically through phases where each phase has a standard set of outputs • Produces project deliverables • Uses deliverables in implementation • Results in actual information system • Uses gradual refinement
Planning • Identifying business value • Analyze feasibility • Develop work plan • Staff the project • Control and direct project
Planning—steps & deliverables • Describe the principal steps in the Planning Phase. What are the major deliverables?
Analysis • Analysis • Information gathering • Process modeling • Data modeling
Analysis—steps & deliverables • Describe the principal steps in the Analysis Phase. What are the major deliverables?
Design • Physical design • Architectural design • Interface design • Database and file design • Program design
Design—steps & deliverables • Describe the principal steps in the Design Phase. What are the major deliverables?
Implementation • Construction • Installation
Implementation—steps & deliverables • Describe the principal steps in the Implementation Phase. What are the major deliverables?
Process Product Project Plan System Proposal System Specification New System and Maintenance Plan Planning Analysis Design Implementation Processes and Deliverables
Methodologies • What is a methodology? • A formalized approach or series of steps • Writing code without a well-thought-out system request may work for small programs, but rarely works for large ones. • A defined methodology is needed for large projects • Alternative methodologies • Structured (Waterfall) methodology • Prototype-based methodology • Rapid Application Development (RAD) methodology • Object-Oriented methodology
Pros and Cons of the Waterfall Methodology Pros Cons Identifies systems requirements long before programming begins Design must be specified on paper before programming begins Long time between system proposal and delivery of new system
Critical elements JAD (joint application development) sessions Fourth generation/visualization programming languages CASE (computer aided software engineering) tools Code generators RAD Methodology
Object-Oriented Methodology • Attempts to balance emphasis on data and process • Uses Unified Modeling Language (UML) for diagramming • Use-case Driven • Architecture Centric • Iterative and Incremental
Key Object-Oriented concepts • Classes -- template to define objects • Instances -- specific examples of class members • Objects -- building block of the system • Attributes -- describe data aspects of the object • Methods -- the processes the object can perform • Messages -- instructions sent to or received from other objects
PATIENT -Name -Birthdate -Phone Number +Insert ()() +Delete ()() A Class and Its Objects Instantiated Objects of the Class PATIENT 1: TOP PACKAGE: PATIENT -Name = Teresa Marks -Birthdate = March 16, 1975 -Phone number = 314-997-3456 Class Attributes PATIENT 2: TOP PACKAGE: PATIENT -Name = Mel Bourne -Birthdate = May 11, 1965 -Phone number = 314-997-3219 Methods
_______________ is the principle that only information required to use the object is available outside the object ______________ is the mechanism that combines data and processes in a single object Class hierarchy, inheritance, and polymorphism Additional O-O concepts
_________________(What O-O concept does this diagram depict?)
_________________(What O-O concept does this diagram depict?)
_________________(What O-O concept does this diagram depict?)
Project Team Roles • Business analyst • System analyst • Infrastructure analyst • Change management analyst • Project manager
Summary -- Part 1 • The Systems Development Lifecycle consists of four phases: Planning, Analysis, Design, and Implementation • There are three major developmentmethodologies: the waterfall method, RAD, and the Object-Oriented approach. • Advantages of Object-Oriented approach are: increased system modularity, reusability, and more realistic way of viewing the system
Summary -- Part 2 • There are six major elements in Object-Oriented design: classes, objects, instances, attributes, methods, and messages. • Encapsulation, Inheritance, and Polymorphism are also important object-oriented concepts • There are five major team roles: business analyst, systems analyst, infrastructure analyst, change management analyst and project manager.
