1 The System life cycle 16 The system life cycle is a series of stages that are worked through during the development of a new information system. A lot of time and money can be wasted if a system is developed that doesn’t work properly or do exactly what is required of it. A new system is much more likely to be successful if it is carefully planned and developed

2 Requirements Analysis and Feasibility Study Implementation Design Analysis Maintenance The stages of the system life cycle

3 Requirements Analysis Fact Finding –Interviews –Questionnaires –Observation –Existing documentation

4 Feasibility study The first stage of the system life cycle This is an investigation that is carried out by a systems analyst to find out what the main problems are with the existing system and if it is technically possible and cost- effective to solve these problems by developing a computer based solution.

5 Feasibility Study Technical –Software –Hardware Social –Redundancies –Retraining –New jobs –Unions negotiations Economic –Financial Costs –Financial Benefits

6 Feasibility report contents COST AND BENEFIT ANALYSIS A description of the existing system outlining what is being done and how it is being done; A set of problem statements describing exactly what the problems are with the existing system; A set of system objectives which describe what the new system must be able to do; A description of some alternative solutions; A description of the technical, economic, legal and social factors that have been considered; A recommended course of action.

7 Analysis During the analysis stage systems analysts investigate the existing system to identify exactly what the problems are with the existing system Systems analysts will use a variety of fact-finding methods to gather more information

8 Detail investigation of hardware and software Data Modelling Staffing structures

9 Reasons Which Influence Choice Costs Ease of use Performance Reliability Software limitations Expandability Response times Security Compatibility with existing hardware and software

10 Data Flow diagrams and systems flowcharts Once the systems analysts have completed their investigation they produce a detailed description of how the existing system works. Methods used to help describe the system include data flow diagrams and systems flowcharts

11 Symbols used in DFDs External entity – data source or data destination, for example people who generate data such as a customer order, or receive information such as an invoice. Process – an operation performed on the data. The two lines are optional; the top section of the box can be used to label the process, the middle to give a brief explanation, the bottom to say where the process takes place. Data store – such as a file held on disk or a batch of documents Data flow – the arrow represents movement between entities, processes or data stores. The arrow should be labelled to describe what data is involved.

12 Data flow diagram for a theatre booking system. Customer Check bookings Available seats Customers Plays Make booking Print tickets Customer Ticket requirements Bookings Title, price, time Name, address, credit card Ticket details Customer ID, seat numbers, time, date, play ID Seat numbers, time, date, play title

13 The symbols used in flowcharts

14 A systems flowchart

15 Design Alternative possible solutions are identified Alternative solutions evaluated The best solution is identified A design specification is produced containing information about: Input Output Data storage User interface Backup and recovery procedures Security procedures Test plan

16 Programming and Testing Typical format for a test plan Test No Test Data Purpose Expected Result Actual Result 1 Enter incorrect mark ‘–1’ Test input mark function Mark rejected 2 Enter incorrect mark ‘45’ Test input mark function Mark accepted 3 Enter new student with student_number ‘100’ forename ‘David’ surname ‘Cooke’ Test ‘Add new student’ function ‘David Cooke’ added to the student database

17 Implementation This stage involves: Setting up the system so that it matches the design specification Testing carried out using the plan to make sure that all the parts of the system work correctly with normal, extreme and erroneous data Normal test data is used to check that a system can handle the sort of data that would be expected during day-to-day use Extreme test data is used to check that a system can cope with data that lies on the boundaries of what is acceptable Erroneous (or exceptional) test data is used to check that a system can identify data that is wrong and reject it

18 Testing using normal, extreme and erroneous data Test No Test Data Purpose Expected Result Actual Result 1Enter a mark of ‘50’ ; this is within the range Test input mark function Mark accepted 2Enter a mark of ‘0’ ; this is on the limit of the range Test input mark function Mark accepted 3Enter a mark of ‘100’ ;this is on the limit of the range Test input mark function Mark accepted 4Enter a mark of ‘101’ ;this is out of the range Test input mark function Mark rejected

19 User participation and training In house training Sent on courses Ergonomics Build user confidence in new system

20 Installing the new system Might include: Installing any new hardware and software Transferring data from the existing system to the new one Training users how to operate the new system

21 Installing the new system (cont’d) There are many different ways that a new information system can be introduced. Some of the more common ones are: Direct Implementation – Change from the old system one day to using the new one the next Parallel Implementation – Use the new system and the old system alongside each other for a short period of time. Pilot and Phased Implementation – Involves introducing the new system in smaller parts while leaving the remaining parts of the old system in place.

22 Direct changeover Change from the old system one day to using the new one the next POS systems Realtime applications –Booking systems –Process control

23 Parallel Running Use the new system and the old system alongside each other for a short period of time.

24 Pilot and Phased Pilot Only a part of the organisation has a new system e.g. personnel department Phased Only some files are computerised eg payroll files

25 Technical Documentation The system design specification: systems flowcharts data flow diagrams Files and data dictionaries Coding and passwords Version control a description of the various parts of the system and what each one does screen layouts and user interface designs the test plan and test data

26 User documentation »a description of what the system is designed to do »minimum hardware and software and operating system requirements of the system »instructions on how to load and run the system »detailed instructions on how to operate each part of the system »Error messages, their meaning and how to deal with them »Backup and recovery procedures »Where to get more help, such as telephone support lines and on-line tutorials

27 Post-implementation review Carried out after the new system has been running for a few weeks or months to identify any modifications that may need to be made.

28 Perfective Adaptive Corrective Maintenance

29 Evaluation Observation Staff ease of adoption Customer satisfaction Log of faults reported

30 What could go wrong? Cost exceeds estimates Poor design leads to not all processes included Technically good but users can’t use it. Crash with unexpected input eg empty file

31 Avoiding post implementation costs Initial detailed thorough analysis and agreement on aims Detailed design Consult staff and unions Allow for future expansion

32 Systems Analyst Involvement After Implementation Training users Evaluation of final system Maintenance of the new system