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Requirements Engineering Processes. Requirements engineering process. Requirements elicitation and analysis. Feasibility study. Requirements specification. Requirements validation. Feasibility report. System models. User and system requirements. Requirements document.
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Requirements engineering process Requirements elicitation and analysis Feasibility study Requirements specification Requirements validation Feasibility report System models User and system requirements Requirements document See also the spiral model on page 144
Feasibility studies • “Does the system contribute to the overall objectives of the organization?” • “Can the system be implemented using current technology and within given cost and schedule constraints?” • “Can the system be integrated with other systems which are already in place?” (should take about 2-3 weeks)
Requirements elicitation and analysis • Some difficulties: • Stakeholders in general don’t know what they want from a computer system except for “general statements” • Requirements are expressed using terms that are specific to the domain (not necessarily familiar for the SE) • Different stakeholders => different set of requirements • Some requirements may be influenced by “political factors” • Some requirements are sensitive to economical and business changes
Requirements elicitation and analysis – Process activities • Requirements discovery: view points, scenarios, interviews • Requirements classification and analysis: clustering into functional / non-functional, use cases • Requirements prioritization and negotiation: back to customer • Requirements documentation
Requirements validation • Validity checks • Consistency checks • Completeness checks • Realism checks • Verifiability checks
Requirements validation - techniques • Requirements review • Step by step reading of requirements • Check for: • Verifiability • Comprehensibility • Traceability • Adaptability • Prototyping • Test-case generation
Requirements management • With the system in use new requirements can appear: • New needs and priorities • Changes on the support balance • Adaptation to end-user needs • Business and technical changes
Requirements management • Requirements can be classified into: • Enduring requirements: relate to core activities of the organization (more stable) • Volatile requirements: relate to external factors and minor activities (susceptible to be changed) • Mutable: related to the environment of the system • Emergent: resulting from ‘learning’ the system • Consequential: following the introduction of the system • Compatibility: related to external systems
Requirements change management • Problem analysis and change specification • Change analysis and costing • Change implementation