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Acquiring software A company or organisation has three basic ways of acquiring (getting) software Buy it from some external source Buy it and customise.

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Presentation on theme: "Acquiring software A company or organisation has three basic ways of acquiring (getting) software Buy it from some external source Buy it and customise."— Presentation transcript:

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

7 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

8 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

9 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

10 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.

11 Buying Commercial Off The Shelf software (COTS)
Initiation Needs Call for Tenders Evaluation & selection Contract negotiation

12 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

13 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

14 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

15 Feedback Plan Analysis Design Development Testing Implementation &

16 Step 1. Feasibility study
The goal of this phase is to determine the problem and is sometimes called the preliminary Investigation or system survey.

17 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 Marketing I. Simon Purchase R. South Sales O. Pine Pay. J. Ria IT. V. Gear

18 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

19 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

20 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

21 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).

22 User Involvement To overcome reluctance to change, involve the people in the client organization in the development process.

23 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

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

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

26 Flowchart Symbols Process Start/Stop Connector Input/Output
Flow direction Decision

27 Flowchart Symbols Start Deposit Show message Get amount No Valid ? Yes
Add balance & amt 22 Show new balance

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