Page 98 - DCAP405_SOFTWARE_ENGINEERING

Unit 6: Requirement Engineering

number of such values. Typical software has a large number of requirements, and the emphasis Notes
is shared between performing the numerical quantification and managing the complexity of
interaction among the large number of requirements.

!
Caution So, in software engineering jargon, “software requirements specification” typically
refers to the production of a document, or its electronic equivalent, which can be
systematically reviewed, evaluated, and approved.

For complex systems, particularly those involving substantial non-software components, as
many as three different types of documents are produced: system definition, system
requirements, and software requirements. For simple software products, only the third of these
is required.
There are some approaches to requirements specification:

Natural language
Structured natural language
Design description language

Requirements specification language
Graphical notation
Formal specification

6.3.5 Requirements Validation

Concerned with whether or not the requirements define a system that the customer really
wants.

Requirements error costs are high, so validation is very important. (Fixing a requirements
error after delivery may cost up to 100 times that of fixing an error during implementation.)

Requirements Checking

Validity: Does the system provide the functions which best support the customer’s needs?

Consistency: Are there any requirements conflicts?
Completeness: Are all functions required by the customer included?
Realism: Can the requirements be implemented given available budget and technology?
Verifiability: Can the requirements be tested?

Requirements Validation Techniques

Requirements reviews/inspections: systematic manual analysis of the requirements.

Prototyping: using an executable model of the system to check requirements.
Test-case generation: developing tests for requirements to check testability.
Automated consistency analysis: checking the consistency of a structured requirements
description.

LOVELY PROFESSIONAL UNIVERSITY 91