Collaborative Environments: Accessibility and Usability for Users with Special Needs - Community-Built Databases: Research and Development - page 324

13.3 State of the Art in Usability Models and Accessibility
Usability is related to how a software enables a group of users to achieve specific
goals in a specific use context. By contrast, accessibility is used to describe the degree
to which a product, device, or service is accessible to as many people as possible.
The purpose of this section is first to present the current models that should be
considered when designing and developing collaborative environments and then to
present the W3C guidelines for making interactive environments accessible to all
produsers, including those with special needs.
13.3.1 Usability in Traditional Interactive Environments
The success of an interactive system depends on a number of different factors,
including functionality, performance, cost, reliability, maintenance, and usability.
All these factors are of quite equal importance, and a serious failure in any one of
them can cause a failure of the system as a whole. Currently, some researches
[ 18 , 21 ] have highlighted a growing recognition that the success of an interactive
system depends to a significant degree on its usability. The ISO 9241-11 standard
[ 15 ] provides the following usability definition: “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”.
According to this definition, the design process of usable interactive systems
cannot be based only on a personal designer's experience and intuition. The
literature offers many models and standards containing principles for good interface
design that can provide helpful guidelines for designers. Examples of standard
include the ISO/IEC 9126-1 [ 16 ], which identifies usability as one of six different
software quality attributes. Moreover, several models proposing different sets of
attributes of usability that can be used in order to evaluate or to support the design
of interactive environments have been defined in the literature (e.g., [ 22 , 26 , 28 ,
29 ]). For example, Nielsen [ 22 ] proposes a set of ten heuristics (see Table 13.3 )
related to the efficiency in use, the learnability, the safety strategies to prevent
errors and the satisfaction. Instead, Shneiderman [ 29 ] and Preece [ 26 ] describe the
same issue using different parameters (i.e., speed of performance or throughput
instead of efficiency in use).
The problem is that these standards and models suggest similar usability attri-
butes using a different terminology with the result of increasing confusion in the
activities of designers and developers alike. In order to address this problem, Seffah
in [ 27 ] defines a consolidated model, redefined and extended by Holzinger in [ 14 ],
about usability measurement with consistent terms for usability attributes and
metrics. The model, named quality in use integrated map (QUIM) [ 27 ], is com-
posed of eleven factors representing different facets of usability that are based on
the main usability guidelines expressed in standards and models presented in the
literature. The model refines these factors and expresses them as criteria and then