Specify

HCD Activity 2: Specify the user requirements

The ISO 9241-210 schematic diagram with the Speciy activity highlighted.Based on the analysis of the previous phase, the specification of the interaction design aspect of the project is set out.  This becomes a ‘contract’ that the interaction designer undertakes to fulfil in the creation of the design.  This has advantages for both parties; the project sponsor knows what they will be getting and the interaction designer knows when they have finished; in interaction design, there is always some improvement or tweak that could be made.

The HCD standard requires that the user requirements specification includes:

  • The intended context of use
  • Requirements derived from user needs and the context of use
  • Requirements arising from relevant ergonomics and user interface knowledge, standards and guidelines
  • Usability requirements and objectives, including measurable usability performance and satisfaction criteria in specific contexts of use
  • Requirements derived from organisational requirements that directly affect the user.

Also the specification should be:

  • Stated in terms that permit subsequent testing
  • Verified by the relevant stakeholders
  • Internally consistent
  • Updated as necessary during the life of the project.

There is a standard to support this: NISTIR 7432 Common Industry Specification for Usability-Requirements.

2.1      NISTIR 7432 Common Industry Specification for Usability-Requirements

This standard was designed to support the preceding standard ISO 13407, and it feeds into ISO/IEC 25062 Common Industry Format for Usability Test Reports, described section 5 below.

It incorporates the notion of ‘levels of compliance’ the specification becoming firmer as the analysis and design process clarifies issues.

A graphic depicting the three levels of compliance described in the standard.[NISTIR 7432 Common Industry Specification for Usability-Requirements]

Requirements might be developed to:

  • Level 1 during HCD Activity 1: Understand Context of Use
  • Level 2 during HCD Activity 2: Specify Requirements
  • Level 3 during HCD Activity 4: Evaluate Designs.

The documentation to be produced consists of 3 parts:

  • The Context of Use
  • Performance and Satisfaction Criteria
  • Test Method and Context for Testing

The Context of Use describes:

  • Stakeholders
  • User groups
  • Goals and tasks
  • Technical environment (equipment)
  • Physical and social environments
  • Scenarios of use for the most important goals
  • Training (If relevant)

The Performance and Satisfaction Criteria becomes more specific as the level of compliance increases.

Level 1 Describe:

a)   Type of criteria appropriate

b)   Relative importance to success of product

Level 2 Describe: Target values for criteria

Level 3 Describe: Specific criterion values

The Test Method and Context for Testing is elaborated further at each level of compliance.

Level 1: Identify evaluation methods

Level 2: Specify a preliminary usability evaluation method

Level 3: Specify a complete usability test method

A Microsoft® Word template for the Usability Requirements Document based on that given in NISTIR 7432 is available in the folder containing this document.

References

NISTIR (2007). NISTIR 7432 Common Industry Specification for Usability-Requirements. [online] Available at: <http://zing.ncsl.nist.gov/iusr/documents/CISU-R-IR7432.pdf>

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