Among all information systems that are nowadays available, web sites are
definitely the ones having the widest potential audience and the most
significant impact on the everyday life of people. Web sites contribute
largely to the information society: they provide visitors with a large
array of services and information and allow them to perform various
tasks without prior assumptions about their computer literacy. Web sites
are assumed to be accessible and usable to the widest possible audience.
Consequently, usability has been recognized as a critical success factor
for web sites of every kind. Beyond this universal recognition,
usability still remains a notion that is hard to grasp. Summative
evaluation methods have been introduced to identify potential usability
problems to assess the quality of web sites. However, summative
evaluation remains limited in impact as it does not necessarily deliver
constructive comments to web site designers and developers on how to
solve the usability problems. Formative evaluation methods have been
introduced to address this issue. Evaluation remains a process that is
hard to drive and perform, while its potential impact is probably
maximal for the benefit of the final user. This complexity is
exacerbated when web sites are very large, potentially up to several
hundreds of thousands of pages, thus leading to a situation where eval-
uating the web site is almost impossible to conduct manually. Therefore,
many attempts have been made to support evaluation with: - Models that
capture some characteristics of the web site of interest.
