Requirements Engineering Process What is requirements engineering? It is the process of discovering, analyzing, documenting and validating the requirements of the system 5 important activities: Feasibility study Requirements elicitation and analysis Requirements validation Requirements management

Requirement engineering

Feasibility studies A feasibility study decides whether or not the proposed system is worthwhile A short focused study that checks If the system contributes to organisational objectives If the system can be engineered using current technology and within budget If the system can be integrated with other systems that are used Doing the study Consult information sources: managers, s/w engineers, end users… Based on information collection (interviews, surveys, questionnaires…) Should be short (2-3 weeks)

Feasibility study implementation Based on information assessment (what is required), information collection and report writing Questions for people in the organisation What if the system wasn’t implemented? What are current process problems? How will the proposed system help? Is new technology needed? What skills?

Feasibility study implementation What will be the integration problems? What facilities must be supported by the system? What is the risk associated with cost and schedule? What are the potential disadvantages/advantages? Are there legal issues? Are there issues linked with the fact that this is an offshore project?

Requirements Elicitation and analysis Sometimes called requirements elicitation or requirements discovery Involves technical staff working with customers to find out about the application domain, the services and the system’s operational constraints May involve end-users, managers, engineers involved in maintenance, domain experts, trade unions, etc. These are called stakeholders

Problems of requirements analysis Stakeholders don’t know what they really want Stakeholders express requirements in their own terms Different stakeholders may have different requirements Organisational and political factors may influence the system requirements The requirement changes during the analysis process.

Requirement elicitation and analysis process Requirement discovery Requirement classification and organization Requirement prioritization and negotiation Requirement documentation

Activities are Requirement discovery-process of interacting with stakeholders to collect their requirements. Requirement classification and organization – takes the unstructured collection of requirements,groups related requirements and organizes them. Requirement prioritization and negotiation – prioritizing requiremetns and finding and resolving requirements conflicts through negotiation . Requirement documentation –requirements are documented and given as input into next round of the spiral .

Requirements discovery It is the process of gathering information about the proposed and existing systems and distilling the user and system requirements from this information. Sources of information during this phase include documentation, system stakeholders and specification of similar systems.

Different stakeholders for a bank ATM For example Different stakeholders for a bank ATM Bank customers Representatives of other banks Hardware and software maintenance engineers Marketing department Bank managers and counter staff Database administrators and security staff Communications engineers Personnel department Elicitation and analysis Viewpoint oriented elicitation

Ethnography It is an observational technique that can be used to understand social and organizational requirements. Ethnography is particularly effective at discovering two types of requirements. 1.Requirements that are derived from the way in which people actually work. 2.Requirements that are derived from cooperation and awareness of other people’s activities.

Requirements validation Concerned with demonstrating that the requirements define the system that the customer really wants Requirements error costs are high so validation is very important

Requirements checking includes Validity Check. The system should provide the functions which best support the customer’s needs. Consistency Check. requirements in the document should not conflict. Completeness Check.The requirements document should include requirements,which define all functions and constraints required by the customer. Realism Check.The requirements can be implemented with given available budget and technology. Verifiability.The delivered system should meet specified requirement.

Requirements validation Techniques can be used. 1 Requirements validation Techniques can be used. 1.Requirements reviews – The requirements are analyzed systematically by a team of reviewers. Reviewers may also check for Verifiability-Is the requirements testable? Comprehensibility- Is the requirement properly understood by the end users? Traceability- Is the origin of the requirement clearly stated? Adaptability- Is the requirement adaptable? 2.Prototyping – The customers and end users can experiment with this model to see if it meets their real needs. 3.Test case generation–Requirements should be testable.

Requirements Management It is the process of understanding and controlling changes to the requirements during the requirements engineering process and system development. The requirements for large systms are always changing.

As the requirement definition is developed, you normally develop a better understanding of user’s needs. Initial requirements Changed understanding of problem Initial understanding of problem Changed requirements Time Requirements Evolution

Enduring and volatile requirements Enduring requirements. These are the stable requirements derived from the core activity of the customer organization. E.g. a hospital will always have doctors, nurses, etc. May be derived from domain models Volatile requirements. These are requirements which change during development process or when the system is in use. In a hospital, requirements may be derived from government health-care policies.

Requirements management includes planning and change management. Requirements management planning: Planning is a first stage in the requirement management process. You have to decide on : Requirements identification: The requirements are individually identified. A change management process: This is the set of activities to assess the impact and cost of changes. Traceability policies: These policies define the relationships between requirements and between the requirements and the system design. CASE tool support: Tools that may be used the range from requirement management system to spreadsheets and simple database systems. Requirements management Enduring and volatile requirements Requirements management planning

Traceability Source traceability information There are three types of traceability information that may be maintained: Source traceability information Links the requirements to stakeholders who proposed these requirements Requirements traceability information Links dependent requirements within the requirements document. Design traceability information Links the requirements to the design modules where these requirements are implemented.

Requirements change management ssss Identified problem Problem analysis and change specification Change analysis and costing Change implementation Revised requirements

Requirements change management Should apply to all proposed changes to the requirements Principal stages Problem analysis and change specification. Requirements problems and propose changes are analyzed. Change analysis and costing. Effects and costs of change are Assessed on requirements Change implementation. Requirements document ,system design and implementation are Modified.