Lecture 5 Requirements Capture

In This Lecture You Will Learn:

Identifying what a new system should be able to do
The user requirements can be classified in different ways
Each of the fact-finding techniques has advantages and disadvantages and its appropriateness for different situations.

The existing system may be manual system, based on paper documents, forms and files, it may already be partly computerized
It is important that the analysts, gathering information as one of the first steps in developing a new system, gains a clear understanding of how the existing system works
A case can be made for investigating the existing system:
- a) Some of the functionality of the existing system will be required in the new system
- b) Some of the data in the existing system is of value and must be migrated into new system
- c) Technical documentation of existing computer system may provide details of processing algorithms that will be needed in the new system
- d) The existing system may have defects which we should avoid in the new system
- e) To understand the organization in general
- f) Parts of the existing system might retained
- g) Understand how people use the system at present

Reasons for changes:

Rapidly Changes - based on economies around the world change dramatically and at short notice, the fortunes of large companies which may be organization’s suppliers, customers or competitors can be transformed overnight.
New technologies are introduced which change production process, distribution networks and the relationship with the introduce legislation that has an impact on the way that business is conducted
Internal factors to grow and change the ways in which they operate and this too provides a motivation for the development of new IS

Whether we are investigating the working of existing system or the requirements for the new system, the information system you gather will fall into one of the 3 categories:
Functional requirements, non-functional requirements and usability requirements.

Describe what the system does or is expected to do, often referred to as its functionality.
In OOAD, use case is used to document the functionality of the system.
Functional requirements include:
- a) Descriptions of the inputs into the system from paper forms and documents, from interactions between people such as telephone calls and other systems
- b) Details of the processing which the system will be required to carry out
- c) Details of the outputs that are expected from the system in the form of printed documents and reports, screen displays and transfers to other system.
- d) Details of data that must be held in the system

Describe aspects of the system that are concerned with how it provides the functional requirements
Items included here:
- a) Performance criteria such as desired response times for updating data in the system or retrieving data from the system
- b) Anticipated volumes of data, either in terms of throughput or of what must be stored
- c) Security considerations

To ensure that there is a good match between the system that is developed and both the users of that system and the tasks that they will undertake when using it.
Gather the following types of information:
- Characteristic of the users who will use the system
- Goals to achieve (tasks undertake)
- Situations which could arise during system use
- Acceptance criteria

A variety of stakeholders:
- senior management—with overall responsibility for the organization
- financial managers—who control budgets
- managers of user departments
- representatives of users of the system
Different roles:
- subjects of interviews
- representatives on project committees
- evaluators of prototypes
- testers
- as trainees on courses
- end-users of new system

Documentation should follow organizational standards
CASE tools that produce UML models maintain associated data in a repository
Some documents will need separate storage in a filing system:
- interview notes
- copies of existing documents
- minutes of meetings
- details of requirements
Documents should be kept in a document management system with version control
Use use cases to document functional requirements
Maintain a separate requirements list
Review requirements to exclude those that are not part of the current project

IS professionals need to record facts about the organization they are studying and its requirements
Standards are important as they promote communication in the same way as a common language
In here, we will be using UML (unified Modeling language) since it is used in the developing industry.
UML consists of a graphical language represent the concepts that we require in the development of an object-oriented information system.
Diagrams in a modeling language such as UML also conform to agree standards. Diagrammatical models are used extensively by system analysts and designers in order to:-
- a) communicate ideas
- b) generate new ideas and possibilities
- c) test ideas and make predictions
- d) understand structures and relationships
Computer-Aided Software Engineering (CASE) tools are used to draw these diagrams and to maintain the associated about the various things that are shown in the diagrams.
Modeling techniques should aid:
- a) Simplicity of representation - only showing what needs to be shown
- b) Internal consistency - within a set of diagrams
- c) Completeness- showing all that needs to be shown
- d) Hierarchical representation - breaking the system down and showing more detail such as lower level