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The Information Systems Life Cycle. Databases & Information Systems Lachlan M. MacKinnon. Why another lifecycle?. We have seen various types of software lifecycle These concentrate on design and implementation of a software system Now we are considering the whole information system
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The Information Systems Life Cycle Databases & Information Systems Lachlan M. MacKinnon
Why another lifecycle? • We have seen various types of software lifecycle • These concentrate on design and implementation of a software system • Now we are considering the whole information system • Software is usually involved But not always!
The system context • These models lack an overall picture of the organisation and its business processes • A traditional structured design method extended in this manner is shown next (Based on Avison and Shah) • The similarities are clear • So are the new features
Problems with existing system New business opportunities Information Systems lifecycleAfter Avison and Shah p71 IS planning Managerial directive Feasibility study Feasibility study report Systems investigation User requirements Project plans Resource requirements Staff assignment Methods and tools Current system data flow Systems analysis System requirements Systems design New system data flow System specification Training and test plans Implementation Programs Procedures Documentation New system in operation Review and maintenance Evaluation report New problem statement?
What’s similar? • Stages rather like waterfall • Repeats with review like spiral • Progress in terms of artefacts
What’s added? • Feasibility study • Review during maintenance • System is an open one • Operation feeds back to design
Feasibility study • Propose and evaluate alternatives • Establish priorities • Gather information • Perform cost-benefit analysis • Form options for computerisation • Present conclusions The negative option is a valid option!
Review during maintenance • Learning from experience • Effectiveness of the solution • Correctness of function • Efficiency • Suitability for the business process • Effectiveness of the process • Kept to time? • Kept to budget? • Lessons learned for future developments
System is an open one • Take account of influences from the organisation which change over time • Managerial directives • often arbitrary • but often dominate decision making • New opportunities • business process change requires system change • Longer term information systems planning • system change to maintain business process
Operation feeds back to design • Operation reveals errors - “maintenance” in SE • Operation reveals bottlenecks for the business • Operation reveals new opportunities for business • Operation reveals difficulties for users
Methodologies and models • A methodology (more properly a method!) is a collection of tools and techniques which help to make IS development more systematic • Typically a methodology defines a process by which an IS system can be built • Typically a process is defined by the artefacts required to be produced - models, documents, plans etc. • The same models etc maybe used in different methodologies
Managing the process • Management requires • an estimate of the resources required for the project • a plan for carrying out the project • a set of milestones and deliverable to assess the plan • The estimation stage is the most difficult • A variety of software metrics have been developed to assist in estimation for projects (Rick Dewar will cover these later)
Problems with existing system New business opportunities IS planning • scope • objectives • budget Feasibility study Management • information needs • operation of current • system Systems investigation Users • investigation • analysis • requirements Systems analysis Analysts • program design • testing • system implementation Systems design Programmers • test system • initialise system • input data • use information Implementation Users Review and maintenance • ensure smooth running • fix faults Operators and technicians The role of people in IS development Managerial directive
Improving the process • As well as models to support the development process, there is a growing interest in models to support the improvement of the process • The Capability Maturity Model (CMM) is a widely used model of how well controlled an organisation’s processes are • CMM defines five levels of maturity in an organisation’s processes and provides a guide to improvement
Reading • Avison and Shah Chapter 3 • Key Practices of the Capability Maturity Model, Vsn 1.1Mark C. Paulk, Charles V. Weber, Suzanne M. Garcia, Mary Beth Chrissis, Marilyn Bush, Software Engineering Institute, Carnegie Mellon University, CMU/SEI-93-TR-25 ESC-TR-93-178, http://www.envisage-inc.com/OnlineLib/SEIdocs/tr25.html