Requirement Engineering Processes

• The processes used for requirements engineering vary widely depending on the application domain, the people involved and the organization developing the requirements.
• The goal of this stage of the software engineering process is to help create and maintain a system/software requirements document.

Processes

1. Requirements Elicitation

• What services do the end-users require of the system?

2. Requirements Analysis

• How do we classify, priorities and negotiate requirements?

3. Requirements Validation

• Does the proposed system do what the user require?

4. Requirements Management

• How do we manage the (sometimes inevitable) changes to the requirements document?

Four High-Level Activities

• Feasibility Study
• Elicitation and Analysis
• Specification
• Validation

Feasibility Study

• A short, focused study that should take place early in the requirement engineering process. It should answer three key questions:
  • does the system contribute to the overall objectives of the organization?
  • can the system be implemented within schedule and budget using current technology?
  • can the system be integrated with other systems that are used?

Elicitation and Analysis

• Software engineers work with customers and system end-users to find out about the application domain, what services the system should provide, the required performance of the system, hardware constraints, and so on.
• Stakeholders (end-users, managers, engineers) also may involve in maintenance, domain experts, trade unions, etc.

Specification

  graph LR
  rd[1.Requirements Discovery]
  rcao[2.Requirements Classification and Organization]
  rpan[3.Requirements Prioritization and Negotiation]
  rs[4.Requirements Specification]

  rd-->rcao-->rpan-->rs-->rd

• Requirement Discovery: Interact with stakeholders of the system to discover their requirements.
• Requirements Classification and Organization: Take the unstructured collection of requirements, groups related requirements, and organizes them into coherent clusters.
• Requirements Prioritization and Negotiation: This activity is concerned with prioritizing requirements and finding and resolving requirements conflicts through negotiation.
• Requirements Specification: The requirements are documented and input into the next round of the spiral.

Requirements Validation

• Requirements validation is the process of checking a software system meets specification, what the customer needs.

Types of Validation

• Validity Checks: A user may think that a system is needed to perform certain functions.
• Consistency Checks: Requirements in the document should not conflict.
• Completeness Checks: The requirements document should include requirements that define all functions and the constraints intended by the system user.
• Realism Checks: Using knowledge of existing technology, the requirements should be checked to ensure that they can actually be implemented.
• Verifiability: To reduce the potent, system requirements should always be written so that they are verifiable.

Requirements Validation Techniques

• Requirements Reviews: Analyze the requirements systematically, checking for errors and inconsistencies.
• Prototyping: An executable model of the system in question is demonstrated to end-users and customers.
• Test-case Generation: Requirements should be testable.