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Define SRS. Explain characteristics of good SRS.

Software Requirements Specification (SRS)​

A Software Requirements Specification (SRS) is a detailed document that describes all the requirements for developing a specific software product, application, or system. It establishes the basis for an agreement between customers and suppliers on what the software product will do, serving as a blueprint for the development team. The SRS document contains functional and non-functional requirements, constraints, interfaces, and any other information necessary to provide a complete description of what the software should accomplish.

Characteristics of a Good SRS​

A high-quality SRS document should exhibit the following essential characteristics:

1. Correctness​

  • Every requirement stated in the SRS is one that the software should meet
  • Free from errors, misconceptions, and inconsistencies
  • Accurately represents user needs and system capabilities
  • Verified by appropriate stakeholders to ensure accuracy

2. Completeness​

  • Contains all significant requirements (functional, non-functional, design constraints)
  • Defines responses to all possible classes of input data in all possible situations
  • No missing information or TBD (To Be Determined) sections
  • Includes all necessary diagrams, tables, and definitions
  • No statements like "to be determined later" without justification

3. Unambiguity​

  • Each requirement has only one possible interpretation
  • Clear and precise language is used
  • Technical terms are defined in a glossary
  • Requirements are stated in simple, concise sentences
  • Avoids vague terms like "sometimes," "usually," "often," "mostly," etc.

4. Consistency​

  • No requirement conflicts with or contradicts any other requirement
  • Same terms are used throughout to refer to the same items
  • Requirements do not overlap in functionality or contradict each other
  • Attributes of real-world objects are consistent across descriptions

5. Verifiability​

  • Each requirement can be tested or verified through inspection, demonstration, analysis, or testing
  • Criteria for acceptance are clear and measurable
  • Statements are precise enough to be implemented and tested
  • Avoids subjective characteristics that cannot be tested (e.g., "user-friendly," "good")

6. Traceability​

  • Each requirement can be traced to its origin (user need, regulatory requirement, etc.)
  • Each requirement can be traced forward to design elements, code, and test cases
  • Requirements are uniquely identified to enable referencing
  • Changes to requirements can be tracked throughout development

7. Modifiability​

  • Structure and style allow changes to be made easily and consistently
  • Requirements are organized logically, not redundantly
  • Table of contents, index, and explicit cross-references
  • Related requirements are grouped together
  • Changes in one requirement should have minimal impact on others

8. Ranked for Importance and/or Stability​

  • Requirements are prioritized based on importance (e.g., essential, conditional, optional)
  • Stability indicators show likelihood of change (e.g., high, medium, low)
  • Helps manage scope and establish implementation order
  • Facilitates resource allocation and planning

9. Feasibility​

  • Requirements can be implemented within available technology, budget, and schedule constraints
  • Economically viable to implement
  • Technically achievable with available skills and tools
  • Compatible with the development environment

10. Conciseness​

  • Document is easy to read and understand
  • No unnecessary information or redundancy
  • Clear and direct language
  • Well-structured with appropriate use of diagrams and models

11. Design Independence​

  • Focuses on what the system should do, not how it should be implemented
  • Avoids imposing unnecessary design constraints
  • Separates requirements from design solutions
  • Allows developers freedom to create optimal design

12. Understandability by Users​

  • Written in language accessible to all stakeholders, not just technical experts
  • Use cases and examples illustrate requirements in familiar terms
  • Organized from a user perspective
  • Minimal use of technical jargon without explanation

A good SRS serves as a solid foundation for successful software development, facilitating communication between stakeholders and developers while providing a clear reference for testing and validation. When these characteristics are present, the SRS significantly reduces the risk of project failure due to misunderstood or inadequate requirements.