Information Systems Development

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Information Systems Development

• Computers in Business

2
The business systems environment

• Information systems are shaped by the aims and
  objectives of the system
• Development of IS often constrained by secondary
  considerations of the business environment, both
  internal and external to the organisation.
• Constraining factors may be technical, economic,
  political, statutory, social or cultural.
• IS environments can be open or closed.
• Closed information systems are self-contained and
  isolated from external constraints
• Open information systems are influenced by the
  external business environment.

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Layers of the business systems environment
Internal environment
culture
technology
Competitors/owners
Business organisation
Customers/suppliers
politics
economy
government
External environment
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Information systems development

• IS development is a time-consuming and
  cost-bearing process.
• The goals of an IS are paramount in determining
  the scope, shape and nature of the IS to be
  developed.
• Traditional approach to IS development is known
  as the systems development life cycle (SDLC).
• SDLC prevalent in the 1960s and 1970s, and is
  sometimes used as a template for systems
  development today.
• Ultimate aim of all systems development should be
  to build IS that meet the requirements of the
  business end-users and deliver the optimal
  benefits of using a structured systems approach
  to development.

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Traditional systems development life cycle.

• Oldest structured methodology for building IS,
  SDLC approaches the development of IS in a very
  deliberate and methodological way, requiring each
  stage of the life cycle, from inception of the
  idea to delivery date to be carried out rigidly
  and sequentially.
• Known as imperative development, since it is
  imperative (or obligatory) to complete one stage
  before moving on to the next stage of the
  development cycle.
• Originally used in the 1960s to develop
  very-large scale functional business systems.
• Forms the basis of structured systems analysis
  and design methodology (SSADM) used today.

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SDLC

• Four generic stages in the systems development
  life cycle.
• 1. Systems Analysis
• 2. Systems Design
• 3. Systems Implementation
• 4. Systems Evaluation
• Each stage can be broken down into component
  activities
• Known as the Waterfall Approach

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Reasons for IS development

• IS development is a major undertaking for any
  business. What reasons are there for developing
  new IS, or replacing old IS.
• Business is an adaptive activity that must
  constantly change or modify in order for an
  organisation to remain competitive.
• Some reasons for initiating change may include
• Current IS is no longer suitable for its purpose
  or the environment in which it operates. It is
  always valuable to continuously assess the
  effectiveness of IS to establish whether they
  align with the current business requirements. IS
  established under previous business conditions
  may no longer be suitable for the prevailing
  situation.
• IS redundancy. The current system may have
  become redundant sue to technological
  developments. Improvements in hardware, software
  and telecommunications often lead to a
  rationalisation of systems structures and domains
  that allow IT to be exploited for competitive
  advantage.
• Current IS may have become too expensive or
  resource intensive to maintain, which may reduce
  an organisations ability to be flexible and
  competitive.

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Systems analysis

• This stage of IS development involves undertaking
  a feasibility study and systems investigation.
• Feasibility study should investigate the current
  system (if there is one) and ascertain the
  problems and requirements of the old and proposed
  new system.
• Study should determine whether the proposed
  system is viable and workable on the grounds of
  legality, organisational structure, technical
  constraints and cost constraints.
• A report is made ( a feasibility report) and
  based on this a decision whether to continue on
  the next stage of the life cycle.
• Issues commonly addressed in feasibility reports.
• 1) Assessment of existing business systems and
  sub-systems
• 2) Purpose and goals of the system
• 3) The business environment
• 4) Systems integration
• 5) Human, technical and legal constraints
• 6. Cost and return on investment
• Assessment of alternative systems

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Systems analysis II

• Information for the feasibility study is
  collected in a number of ways - interviews with
  colleagues, studying business documentation, etc.
• TELOS, Five main factors to assess the
  feasibility of IS.
• Technical feasibility
• Economic feasibility
• Legal feasibility
• Operational feasibility
• Schedule feasibility
• The systems analysis stage determines the scope,
  objectives and feasibility of proposed systems

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Systems design

• Stage involves designing an IS to overcome a
  particular information-based problem and meet the
  end-users requirements. Stage characterised by
  the separation of the logical from the physical
  design process.
• Logical design process describes the functional
  requirements or purpose of the system. It
  conceptualises what the system should do in order
  to solve the problems identified in the previous
  stage.
• Physical design process follows this and
  describes the physical and technological
  characteristics that the IS should posses.
• Physical aspects of the logical design will
  normally involve consideration of the following
  elements.
• Hardware technology - input, processing and
  output devices.
• Software technology - software applications and
  their integration, specifications, and
  performance within the system
• Storage media - the type, structure and function
  of storage media, such as computer files,
  databases, CD ROMs and other data and information
  storage technology.
• Telecommunications technology - specifications,
  use and characteristics of the technology both
  internally and externally to the organisation
• People and organisation - the description and
  remit of human interaction, plus the procedures
  and control aspects of the organisation that
  impact on the system.

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Implementation stage

• Stage involved with building the components of an
  IS.
• Often involves writing software or the
  integration of pre-coded applications (often
  referred to as applications based development).
• This stage often preoccupied with hardware,
  software and telecommunication considerations.
• The stage deliverable should be the delivery of
  an installed and operational IS that can be
  tested and evaluated.
• This stage usually involves the following
  considerations
• hardware acquisition
• software acquisition
• user familiarisation and training
• environment preparation
• information and data preparation.

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Evaluation Stage

• This stage involves testing and appraisal to
  determine whether the system is meeting its
  requirements.
• An evaluation report should be produced to
  determine whether the system is meeting the
  requirements set out in the initial feasibility
  report efficiently and effectively.
• A number of evaluation techniques may be used,
  these often include
• user evaluation - involves formal and informal
  feedback from the end-user to determine if the
  system is efficient and effective
• cost-benefit analysis - attempts to match the
  aggregate of the costs against the aggregate of
  the benefits of the system.
• benchmark testing - involves comparing the actual
  performance of the system to the ideal standard
  for that system.

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The main strengths the SDLC

• Main strengths that make SDLC relevant to the
  modern business environment
• SDLC is a tried and tested approach that is very
  suitable for the development of large-scale
  information systems
• SDLC relies on the production of systems
  documentation and standards of development that
  can be used to guide the development of an IS and
  can be used as a reference and training material
  for others
• The sequential and phased nature of the SDLC
  allows a complex systems development problem to
  be broken down into manageable and understandable
  tasks
• The SDLC relies on the use of formalised analysis
  and design tools and techniques that graphically
  show the nature of data and information flows
  within that system
• The structured nature of the SDLC allows the
  incorporation of formal project management
  techniques and tools to guide the systems
  development process.

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The main weaknesses of the SDLC

• The SDLC ignores or underplays end-user
  involvement in the systems development process.
  The end-user is often faced with an operating
  system that is user-unfriendly or fails to
  deliver the users requirements for the system.
• Over 90 of computer-based systems development
  occurs within the business environment. The use
  of computer and IT within organisations is based
  on small desktop workstations, usually networked
  locally. SDLC is more concerned with large-scale
  systems development and is not appropriate to
  small-scale PC-based development in business
  information systems.
• SDLC is time-consuming and costly, time and cost
  considerations are paramount in todays business
  environment.
• SDLC is too-rigid to allow systems development
  react to rapidly changing business situations,
  and does not allow changes to be made in IS
  development to exploit new business situations
  quickly.

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Alternative approaches to information systems
development

• The downsizing of IT within the business
  environment and the growth of networked desktop
  computing has seen the traditional SDLC become
  outdated.
• Five alternative approaches to IS development
  are
• 1) Rapid applications development (RAD)
• 2) Joint applications development (JAD)
• 3) Prototyping systems development
• 4) Object oriented systems development (OOSD)
• 5) Business process re-engineering
• All 5 approaches share a common characteristic of
  emphasising the importance of human end-users in
  the development process.

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End-user IS development

• Unlike traditional SDLC approach, where the
  end-user is peripheral to the systems development
  process, in end-user computing the final user of
  the system is central to the development process.
• End-user IS development possible partly due to
  the development of user-friendly
  fourth-generation programming languages.
• Language evolution
• 1GLs Assembler Machine Language Code
• 2GLs FORTRAN
• 3GLs ADA, C, COBOL, Pascal
• 4GLs VisualBasic, Visual C, Small Talk, Simula

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End-user IS development

• 4GLs are less structured, non-procedural, and
  more user-friendly for non-technical business
  specialists
• Less structure means that changes can be made to
  programs at very little cost, and without having
  to go back to the start of the development life
  cycle.
• 4GLs allow standard, pre-programmed applications
  to be customised, rather than starting an IS from
  scratch. Process known as applications-based
  systems development.
• Standard software application packages, I.e.
  Microsoft Office can be linked and integrated
  using 4GL environments such as VisualBasic.
• Advantages to using 4GLs include
• greater end-user involvement in the development
  process
• relatively less program coding with 4GLs than
  3GLs
• user-friendly development tools and environment
• less structured and more flexible design and
  development framework
• shorter development time and faster systems
  delivery

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End-user IS development

• Main tools and techniques of 4GL IS development
  include
• applications-based software development
• rapid applications development (RAD)
• 4GL environments and other software development
  tools
• information systems prototyping
• Software tools include
• software application generators
• visual programming languages
• standard query languages
• graphics languages
• Some weaknesses of using 4GLs include
• the laborious and time-consuming nature of coding
  in 3GLs is often overcome by using support tools
  such as CASE (computer-aided software
  engineering) that reduces time by automatically
  generating language code. This makes programming
  with 3GLs more rational and more productive.
• 3GL programs are often easier to test and
  maintain, as 4GLs often contain hidden
  pre-generated language code.
• 3GL more suitable for very-large
  transaction-based mainframe systems
• User development may lead to IS than are less
  standard, more idiosyncratic than IS build by
  trained systems engineers.