A number of possible definitions of usability are available in the literature of geospatial information, and the needs of spatial data usability have been compared and contrasted with the broader data-related activities of providers and users of [Page 3003]geoinformation. For example, one official definition of usability is given by the ISO 9241–11 standard on Display Screen Regulations, Use of Ergonomics for Procurement and Design. In this definition, system usability consists of the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use, where

• effectiveness measures the accuracy and completeness with which users achieve specified goals,
• efficiency measures the resources expended in relation to the accuracy and completeness with which users achieve ...