Acquiring software

1
Acquiring software

• A company or organisation has three basic ways of
  acquiring (getting) software
• Buy it from some external source
• Buy it and customise (modify) it
• Develop it themselves (in-house or out)
• Some of these three methods are more appropriate
  for different organisations and for different
  types of software

2
Systems Software

• Systems Software includes software like
• Operating Systems,
• File Management Systems and Databases
• Communications and Networking Software
• These are usually
• very complex systems
• purchased from large software developers
• Purchasing may include licensing arrangements

3
Information Systems and Applications

• There are many generic IS applications for
  particular domains / industries
• e.g. banking, insurance, airline reservations
  etc.
• When an organisation perceives a need for an IS
• e.g. starting a new company, migrating from a
  paper based system
• or perceives a need for an improved IS
• e.g. the current system is too slow, incompatible
• the organisation may choose to buy a generic
  application or build a custom application

4
Buying Off The Shelf software

• installed in a matter of weeks or months
• possibly modified - further maintenance and
  development
• tested several times, so it gives more
  refinements better de-bugging and documentation
• a professional team of programmers, designers,
  technical writers
• good documentation
• known price of purchase or license
• generally a better and more economical choice

5
Build (develop) your own software

• The organisation may decide to develop their own
  custom-built IS because generic applications
• are not available or
• do not provide all of the required features
• are not compatible with other existing systems
• Cost saving is not usually a reason because
  building your own is hugely expensive
• Building a custom IS can be done either
• by external consultants or
• in house, by your own IS/IT staff
• end users

6
Knowing what you need

• In either case, the company must know exactly
  what the IS is required to do
• The company may carry out a feasibility study to
  determine if the proposed IS will provide
• significant benefits
• without unacceptable risks
• at an acceptable cost
• The feasibility study would indicate which
  approach - buy or build - is better

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System Requirements

• Whether the organisation decides to purchase or
  develop a system, the organisation now carries
  out a detailed analysis to find out
• the functions that the IS must perform,
• the speed at which it must perform,
• the hardware it will run on and
• the other systems with which it will be compatible

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Functional and Non-functional Requirements

• Individual IS have both functional and
  non-functional requirements
• Non-functional requirements are NOT soft
• A particular IS may need to be highly secure,
  very fast, highly reliable - these are not
  functions the IS performs, so they are
  non-functional requirements.
• These requirements may affect the way searches
  are carried out, the way data is arranged in
  databases and so on. The way non-functional
  requirements are met are often highly technical

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The interface and user centred IS

• A special class of non-functional requirements
  may relate to the user interface
• The interface may be required to be easy to
  learn, easy to use, provide adequate support for
  users.
• These are NOT trivial nor universal requirements.
  They can have a significant impact on the way
  certain functions are implemented or on the
  overall cost and development time for the IS

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Buying and the RFT

• If the company decides to buy an IS they may send
  out a Request for Tenders (RFT or RFP)
• An RFT provides software houses with all the
  requirements for the proposed IS
• Software houses submit tenders which try to
  convince the buyer to choose their software
• The buyer must evaluate these tenders impartially
  or there may be legal implications. If a suitable
  IS is found, the organisation signs contracts to
  buy.

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Buying Commercial Off The Shelf software (COTS)
Initiation
Needs
Call for Tenders
Evaluation selection
Contract negotiation
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Building and the SDLC

• Building an IS is a huge job,
• often involving dozens or hundreds of staff
• lasting moths or years
• costing hundreds of thousand or millions
• Because of this, most organisations follow a
  pattern called the Software Development Lifecycle
  (SDLC) to try to streamline the process and
  ensure success.
• There are a number of variations on the SDLC

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Typical SDLC

• Feasibility study - may already have been done
• Plan - all the steps and
  gather resources
• Analysis - find out exactly what is
  needed
• Design - work out how to build it
• Development - produce the computer code (4GLs)
• Testing - make sure it works
• Validation - make sure it does what is
  required
• Implementation - get the IS into the
  organisation
• Get ready to start again

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SDLC and methodologies

• SDLC is a framework - it tells us about broad
  steps and how to move from one to another
• This may not be sufficient guidance for a large
  project, so some companies buy and use detailed
  sets of instructions, called methodologies
• Methodologies are expensive and require both
  training and commitment e.g. SSADM

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Feedback

• Plan
• Analysis
• Design
• Development
• Testing
• Implementation
• Documentation

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Step 1. Feasibility study

• The goal of this phase is to determine the
  problem and is sometimes called the preliminary
  Investigation or system survey.

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Tools of Feasibility study
Pres. C. Stenos

• The systems analyst will develop an
  organizational chart to identify all relevant
  stakeholders.

VP A. Mapp
VP Z. Hewn
Purchase R. South
Marketing I. Simon
Sales O. Pine
Pay. J. Ria
IT. V. Gear
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Defining the Problem involves

• Nature of the problem
• The systems analyst and the users/clients must
  agree on the nature of the problem.
• Scope of the problem
• Determining the scope of the problem sets
  limitations on how extensive the proposed system
  will be, the eventual budget and project
  schedules
• Objectives of the project
• Determining what the users/clients think the
  system should be able to do

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Step 1b Authorisation Planning
Following the feasibility study, someone in
authority must authorise the project - the
project sponsor A project manager will be
appointed to oversee the planning, resourcing and
progress of the project
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Planning

• Project planning means identifying all the tasks
  (and sub-tasks) that need to be done. The amount
  of time for each of these tasks is estimated.
• A Gantt chart is good for organising the tasks,
  their start/finish dates and the resources they
  need
• Estimation of times is risky so PERT uses 3
  estimates to get the most accurate overall plan
• Critical Path Method (CPM) identifies all the
  tasks which might delay the project so they can
  be watched more closely

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Step 2 Systems Analysis

• Systems analysis is the process of studying an
  existing system to determine how it works and how
  it meets client and user needs.

• Clients contract to have the systems analysis
  done.
• Users are people who will have contact with the
  system (employees and customers).

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User Involvement

• To overcome reluctance to change, involve the
  people in the client organization in the
  development process.

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An analyst must be good at

• coordinating schedules and system-related tasks
  with a number of people.
• communicating -The analyst may need to make oral
  presentations and write reports for clients,
  users, and others involved with the system.
• Other desirable qualities of a systems analyst
  are
• an analytical mind
• self-discipline
• self-direction
• The ability to work without tangible results

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Flowcharts

• A flowchart is a pictorial representation of a
  step-by-step solution to a problem.

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Flowchart Basics

• A flowchart consists of arrows to represent
  direction the program takes and boxes and symbols
  to represent actions.

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Flowchart Symbols
Process
Start/Stop
Input/Output
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Flowchart Symbols
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