CSIS 3600 Systems Analysis and Design The Systems

CSIS 3600 Systems Analysis and Design The Systems Development Life Cycle Intellectual Property of Dr. Meg Murray, dated August 2002

Methodologies, Techniques & Tools The Systems Development structure includes: Methodology Techniques Tools

Methodologies, Techniques & Tools • Methodologies are comprehensive, multi-step approaches that guide the systems development process. Most incorporate many techniques. • Techniques are the particular processes that are used to complete the work of systems development. Techniques describe the activities and tasks that will be employed and define deliverables. • Tools are what you have that help you accomplish your tasks. Many software tools are now available that facilitate the development of deliverables. CASE tools fall under this category.

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 Product Development Methodology is available for review on the class web site.

Methodologies • Most software development consultant agencies use a methodology template. An example is http: //www. prestwood. com/products/psdm/ • A good collection of resources related to methodologies can be found at http: //www. methodology. org • Microsoft serves as a framework for many organizations: http: //www. microsoft. com/business/microsoft/mc s/msf. asp

What are Techniques are the processes used to carry out the methodology. They include: – Project Selection Process – Project Plan – System Requirements Definition – System Models

What are Tools help in the system development process. These tools include CASE tools, diagramming tools, etc. A listing of Case Tools is available at: http: //www. cs. queensu. ca/Software. Engineering/toolcat. html

Structured Design • Projects move methodically from one to the next step • Generally, a step is finished before the next one begins Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Waterfall Development Method Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Pros and Cons of the Waterfall Method 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 Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Systems Development Life Cycle • The SDLC came out in the late 1960 s and early 1970 s and was really the first documented structured approach. • It is very logical and comprehensive. • It grew up in the era of large mainframes but as a framework, it is applicable to today’s distributed systems.

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 Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Systems Development Life Cycle • Six Stage Plan (more general version): I. Preliminary Investigation • gain understanding of problem domain and current organizational environment. II. Systems Analysis • define business requirements, evaluate alternatives, prepare functional requirements III. System Design • define technical specifications IV. System Construction • build or select software, test system and train users V. System Implementation • get the system running and begin to use the system VI. Evaluation • evaluate how the system is meeting objectives and make adjustments

Systems Development Life Cycle I. III. IV. V. VII. Project Identification and Selection Project Initiation and Planning Analysis Logical Design Physical Design Implementation Maintenance (and evaluation)

Systems Development Life Cycle • Four Stage Plan (the short version): – I. Systems Planning – II. – IV. Analysis Systems Design Systems Implementation Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Project Phases • Planning – Why build the system? • Analysis – Who, what, when, where will the system be? • Design – How will the system work? • Implementation – System delivery Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Planning • • • Identifying business value Analyze feasibility Develop work plan Staff the project Control and direct project Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Deliverables Planning – Business Value • Identification and prioritization of information system needs • Problem is identified and articulated • Business case or system justification

Deliverables Planning • Project scope • Project feasibility • Selection of system development participants • Project (work) plan

Analysis • • Analysis Information gathering Process modeling Data modeling Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Deliverables - Analysis • Description of the current system/environment • Determine and structure functional requirements • Identification of alternatives • Initial system models are built – Use case models – Other models (UML – class diagrams, sequence diagrams, etc…

Design • • • Physical design Architectural design Interface design Database and file design Program design Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Deliverables - Design • Technical detailed specifications of all systems elements (programs, files, network, system software, etc. ) • Interface Design • Database and file design

Implementation • Construction • Installation • Maintenance and Evaluation (not outlined in text) Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Deliverables - Implementation • • Software code Documentation Installation plan Testing plan Training procedures Initial support capabilities outlined Maintenance Plan Evaluation Plan

Processes and Deliverables Process Product Planning Project Plan Analysis System Proposal Design System Specification Implementation New System and Maintenance Plan Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Note on Maintenance: – system is systematically repaired and improved. – This is the evolution of the information system and all previous phases are repeated

Concluding Notes on the SDLC The SDLC provides a framework. Systems development is cyclical. Phases overlap and flexibility must be built into the design process. The SDLC provides a convenient checklist of tasks to be undertaken or ignored as appropriate.

Concluding Notes on the SDLC The SDLC is most appropriate in situations where the information systems requirements are predicable (in Transaction Processing and MIS type systems). It can be adapted to meet other needs and parts of the SDLC are included in most all system development methodologies.

Concluding Notes on the SDLC One criticism of SDLC is that it tends to focus too little on good analysis and design resulting in a system that does not match users’ needs and requires extensive maintenance (software repair, patches, etc. ). Some estimates suggest that maintenance costs account for as much as 70% of system development costs.

Alternatives to the SDLC • RAD and JAD – Strategies for reducing the time it takes to deliver systems. Focused on extensive user involvement, prototyping and integrating CASE tools. • Prototyping – iterative process of system development in which a draft working system is developed and modified • Object Oriented Design and Analysis – very similar and incorporates the phases of the SDLC • Agile Methods

Alternatives to the SDLC • Rapid Application Development (RAD) • Phased Development • Prototyping • Throw-Away Prototyping Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Rapid Application Development • Critical elements – CASE tools – JAD sessions – Fourth generation/visualization programming languages – Code generators Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

How Prototyping Works Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Throwaway Prototyping Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Object-Oriented Analysis and Design • Attempts to balance emphasis on data and process • Uses Unified Modeling Language (UML) for diagramming – Use-case Driven – Architecture Centric – Iterative and Incremental • Focus of this course Power. Point Presentation for Dennis, Wixom & Tegardem Systems Analysis and Design Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.

Concluding Notes Not all system requirements can be stated up front, and problems often appear towards the end of the process. Flexibility, common sense and a focus on the goal at hand are the real tricks to making your systems development methodology work.

Quotes of the Week "When a new system concept or new technology is used, one has to build a system to throw away, for even the best planning is not so omniscient as to get it right the first time. The management question, therefore, is not whether to build a pilot system and throw it away. You will do that. The only question is whether to plan in advance to build a throwaway, or to promise to deliver the throwaway to customers. " Brooks cited in Pressman (Software Engineering : A Practitioner’s Approach, 4 th Edition, 1997). -------"When faced with a problem you do not understand, do any part of it you do understand, then look at it again. " Robert Heinlen