Models date from 1960s batch processing systems but still relevant today, but with different emphasis and solutions.
Life cycle includes: Problem definition, feasibility study, analysis, design, production, testing, implementation, maintenance, evaluation.
Information Gathering: based on data collected at site, from two main sources, people and records. Information about current system taken from interviews, questionnaires and observation of current practice.
Documentation: analyst must document system, using diagrams such as system flowchart to illustrate movement of data through organisation and ways they are used.
Feasibility: includes these factors: technical, economic, legal, operational, social (TELOS). Any new system will undoubtedly cost money so costs need to be weighed against benefits. Costs include hardware, software, staff, training, support & maintenance. Likely benefits include: reduced staff (may need more and wage costs of new staff may be higher due to skill levels required), better service, improved availability of information (e.g. library), faster processing so better cash flow (may be crucial to business survival).
Nine features:
May use prototyping (quick trial solutions, using RAD tool - Rapid Application Development). Human-Computer Interface is important, users must find system easy and logical.
Data Model: for modern systems using a DBMS or RDBMS an entity-relationship diagram will be produced.
Software criteria:
Testing strategies:
Test plan and data:
List items to be tested and values that will test them. Show expected results.
Can be done step by step, department by department, in a single changeover or in parallel with existing system.
Install hardware, change office layout and personnel; train users in new system; convert old files to new system.
Very important in verifying system works as required and predicted. Test data should be chosen to show operation under range of circumstances and reaction to bad data.
Does new system meet the specification?
Any program errors?
Is the new system effective? Does it do what it is supposed to do?
Is the new system easy to use and maintain? It may take time to find out!
Types: corrective (fix bugs and errors), adaptive (adapt to new circumstances), perfective (improving the system). Relies on good documentation of system specification, programs, user manual and operations manual.
User and system documentation: system specification; data flow diagrams; purpose of each program; file organisation and contents; program listing; test data and results. Technical documentation should supply all the information that a technical person needs to maintain the system.