The main navigational problems that can arise when using a screen reader or magnifier are lack of context, information overload, and excess of information sequential reading. Our investigation attempts to address these usability problems.
DEFINITION
In order to make Web sites more accessible and usable, we identified 15 criteria. For each criterion one or more checkpoints must be applied:
- Criteria are general principles intended for Web site developers and designers. Such principles should be followed to improve accessibility and usability of Web sites, especially for users who navigate through screen reader.
- Checkpoints are technical solutions that allow the application/evaluation of the proposed criteria. Each criterion is defined by one or more checkpoints.
CLASSIFICATION
We catalogued criteria under three different points of view, necessary to quantify their importance in Web site usability and to formalise an evaluation strategy.
Depending on checkpoints, two kinds of criteria can be distinguished:
- "AND" type criteria: all checkpoints must be applied to satisfy the criterion;
- "OR" type criteria: at least one checkpoints has to be applied to satisfy the criterion.
- on the bases of the main aspects of usability involved, criteria are assigned to three different groups: effectiveness, efficiency, and satisfaction;
- depending on the type of impact on the user interface, criteria are classified and grouped according to four logical dimensions based on general issues which should be taken into account during design of Web sites: structure and arrangement, content appropriateness, multimodal output, and consistency.
EVALUATION
Our criteria can be used to evaluate Web site usability/accessibility. Two complementary approaches can be combined:
- Expert testing (inspection evaluation). A competent tester (confident with criteria) examines several Web sites and checks if and to what extent criteria have been applied by developers.
- User testing. Blind/low vision users test the impact of criteria on web navigation: they are asked to perform assigned tasks while navigating two versions of the same web site, with and without criteria. For each user, the time required to accomplish tasks in the two cases is recorded. The time difference is used as indicator of the influence of criteria on navigation
PAST, PRESENT, AND FUTURE RESEARCH
We tested the validity of our criteria and checked if their application could actually improve blind users' navigation.
- The expert testing (inspection evaluation) revealed that, within tested Web sites, the majority was not sufficiently usable.
- The user testing revealed that the application of our criteria significantly reduced the navigation time required to accomplish several types of tasks.
Given such positive results, we are going no with our research by realizing a new tool MAGENTA. We are also working to the creation of a guideline abstraction language .
For further information please contact
fabio.paterno@isti.cnr.it
and
barbara.leporini@isti.cnr.it