NISTIR 7432
Common Industry Specification for Usability - Requirements
Information Access Division
Information Technology Laboratory
June 2007
NIST
National Institute of Standards and Technology
Technology Administration, U.S. Department of Commerce
Introduction
The Common Industry Specification for Usability - Requirements (CISU-R) helps usability professionals, product managers, and others working in product design and development to create usability requirements.
It sets standards for specifying usability requirements, which include three types of information:
Common Industry Specification for Usability - Requirements
Information Access Division
Information Technology Laboratory
June 2007
NIST
National Institute of Standards and Technology
Technology Administration, U.S. Department of Commerce
Introduction
The Common Industry Specification for Usability - Requirements (CISU-R) helps usability professionals, product managers, and others working in product design and development to create usability requirements.
It sets standards for specifying usability requirements, which include three types of information:
The context of use: the intended users, their goals and tasks, associated equipment, and the physical and social environment in which the product can be used.
Performance and satisfaction criteria: measures of usability for the product.
The test method and context of testing: the method to be used to test whether the usability requirements have been met and the context in which the measurements will be made.
Underlying the specific goals of the standard is a deeper goal of creating useful and usable products that allow users to complete their tasks efficiently, effectively, and with satisfaction.
To support this deeper goal, the CISU-R provides a structure for requirements to help stakeholders:
Document the context of use for a product, including definitions of the expected technical, physical, and social environments, user groups, goals for use of the product and scenarios of use, as defined in Clause 6.2.
Write usability requirements in sufficient detail to make an effective contribution to design and development. (A suggested outline for usability requirements is provided in Annex A.)
Relate usability requirements to stakeholder requirements (including user, customer, and business) for successful use of a product and increased productivity.
Define usability criteria that can be empirically validated. (Annex B provides examples of usability criteria.)
Define the method for testing the product against the criteria. (Annex C identifies the information to be specified for the test method.)
Create requirements that are useful throughout the product design and development process, providing input to the design process early in a project and adding more detailed information about criteria and methods as it is available.
Usability requirements created with the CISU-R can be updated throughout a product’s lifecycle. A project may choose to create complete requirements, including all information specified in the CISU-R, or may adopt a level of conformance that meets stakeholder and business goals.
The CISU-R can help integrate the creation of usability requirements into any design or development process. (Annex D contains an example of a user centered design process that incorporates the development of usability requirements under the CISU-R.)
-Requirements can meet one of three levels of compliance with the CISU-R. Each level builds on the previous one, allowing the usability requirements to be developed over time, with increasing detail and precision. This approach allows the CISU-R to be used for all types of projects, from the smallest or most informal to complex or formally specified products.
-Customers, users, and development teams can use the CISU-R as a communications tool to understand and specify requirements within an organization or as the basis for a contractual relationship between companies. The three levels of compliance provide the flexibility to match the level of detail and formality of the usability requirements to business needs.
-Requirements may also include indirect measures of usability, such as post-release satisfaction tests, or business performance requirements, such as completed transactions. These criteria are not intended for evaluation using a summative usability test, as required by the third level of conformance, but can be useful in establishing business or performance requirements.
-The CISU-R recognizes that usability requirements are just one type of product requirement. They complement functional, business, process, safety, and non-functional (quality) requirements. The information gathered in creating usability requirements can be used to help define other user requirements (for example, for features of the interface). (Annex E lists other types of user and usability requirements.)
The CISU-R focuses on the information needed to create usability requirements that are useful for design and development, rather than dictating a specific process or user centered design activities. (Annex E contains an example of a user centered design process that incorporates the CISU-R.)
-In situations where there are already processes and document formats in place, stakeholders can incorporate the CISU-R into that process by ensuring that the information specified here is included in any usability requirements.
-If there is no established format, requirements can use the information specified in Annex A as a guide. (Examples of all three levels are included in Annexes F, G, and H as a reference.)
The process of creating requirements with the CISU-R can be incorporated into many user centred design processes. For example, in ISO 13407, specifying requirements is one activity in an iterative process. The CISU-R provides details for how to complete this activity, as shown in Figure 1.
To ensure that the requirements are correct, other user centered design activities (such as competitive analysis, interviews, surveys, focus groups, field studies, task analysis, benchmark usability tests, or paper prototyping) can be used early in the development process to obtain feedback from users to iteratively refine requirements.
The CISU-R complements other user centered design standards.
-It uses the definition of usability in ISO 9241-11: the effectiveness, efficiency, and satisfaction with which the intended users can achieve their tasks in the intended context of product use.
-Usability requirements created using the CISU-R are consistent with the recommendations of ISO 13407.
-Usability tests conducted to measure whether usability requirements have been met can be reported using the Common Industry Format (CIF) (ISO/IEC 25062).
-The development of usability requirements may be supported by the use of standards such as ISO 9241 or ISO 9126.
Performance and satisfaction criteria: measures of usability for the product.
The test method and context of testing: the method to be used to test whether the usability requirements have been met and the context in which the measurements will be made.
Underlying the specific goals of the standard is a deeper goal of creating useful and usable products that allow users to complete their tasks efficiently, effectively, and with satisfaction.
To support this deeper goal, the CISU-R provides a structure for requirements to help stakeholders:
Document the context of use for a product, including definitions of the expected technical, physical, and social environments, user groups, goals for use of the product and scenarios of use, as defined in Clause 6.2.
Write usability requirements in sufficient detail to make an effective contribution to design and development. (A suggested outline for usability requirements is provided in Annex A.)
Relate usability requirements to stakeholder requirements (including user, customer, and business) for successful use of a product and increased productivity.
Define usability criteria that can be empirically validated. (Annex B provides examples of usability criteria.)
Define the method for testing the product against the criteria. (Annex C identifies the information to be specified for the test method.)
Create requirements that are useful throughout the product design and development process, providing input to the design process early in a project and adding more detailed information about criteria and methods as it is available.
Usability requirements created with the CISU-R can be updated throughout a product’s lifecycle. A project may choose to create complete requirements, including all information specified in the CISU-R, or may adopt a level of conformance that meets stakeholder and business goals.
The CISU-R can help integrate the creation of usability requirements into any design or development process. (Annex D contains an example of a user centered design process that incorporates the development of usability requirements under the CISU-R.)
-Requirements can meet one of three levels of compliance with the CISU-R. Each level builds on the previous one, allowing the usability requirements to be developed over time, with increasing detail and precision. This approach allows the CISU-R to be used for all types of projects, from the smallest or most informal to complex or formally specified products.
-Customers, users, and development teams can use the CISU-R as a communications tool to understand and specify requirements within an organization or as the basis for a contractual relationship between companies. The three levels of compliance provide the flexibility to match the level of detail and formality of the usability requirements to business needs.
-Requirements may also include indirect measures of usability, such as post-release satisfaction tests, or business performance requirements, such as completed transactions. These criteria are not intended for evaluation using a summative usability test, as required by the third level of conformance, but can be useful in establishing business or performance requirements.
-The CISU-R recognizes that usability requirements are just one type of product requirement. They complement functional, business, process, safety, and non-functional (quality) requirements. The information gathered in creating usability requirements can be used to help define other user requirements (for example, for features of the interface). (Annex E lists other types of user and usability requirements.)
The CISU-R focuses on the information needed to create usability requirements that are useful for design and development, rather than dictating a specific process or user centered design activities. (Annex E contains an example of a user centered design process that incorporates the CISU-R.)
-In situations where there are already processes and document formats in place, stakeholders can incorporate the CISU-R into that process by ensuring that the information specified here is included in any usability requirements.
-If there is no established format, requirements can use the information specified in Annex A as a guide. (Examples of all three levels are included in Annexes F, G, and H as a reference.)
The process of creating requirements with the CISU-R can be incorporated into many user centred design processes. For example, in ISO 13407, specifying requirements is one activity in an iterative process. The CISU-R provides details for how to complete this activity, as shown in Figure 1.
To ensure that the requirements are correct, other user centered design activities (such as competitive analysis, interviews, surveys, focus groups, field studies, task analysis, benchmark usability tests, or paper prototyping) can be used early in the development process to obtain feedback from users to iteratively refine requirements.
The CISU-R complements other user centered design standards.
-It uses the definition of usability in ISO 9241-11: the effectiveness, efficiency, and satisfaction with which the intended users can achieve their tasks in the intended context of product use.
-Usability requirements created using the CISU-R are consistent with the recommendations of ISO 13407.
-Usability tests conducted to measure whether usability requirements have been met can be reported using the Common Industry Format (CIF) (ISO/IEC 25062).
-The development of usability requirements may be supported by the use of standards such as ISO 9241 or ISO 9126.
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