Markel Vigo

Quantitative metrics for measuring web accessibility

This paper raises the need for quantitative accessibility measurement and proposes three different application scenarios where quantitative accessibility metrics are useful: Quality Assurance within Web Engineering, Information Retrieval and accessibility monitoring. We propose a quantitative metric which is automatically calculated from reports of automatic evaluation tools. In order to prove the reliability of the metric, 15 websites (1363 web pages) are measured based on results yielded by 2 evaluation tools: EvalAccess and LIFT. Statistical analysis of results shows that the metric is dependent on the evaluation tool. However, Spearmans test produces high correlation between results of different tools. Therefore, we conclude that the metric is reliable for ranking purposes in Information Retrieval and accessibility monitoring scenarios and can also be partially applied in a Web Engineering scenario.

User-tailored web accessibility evaluations

This paper presents a framework and system to evaluate the accessibility of web pages according to the individual requirements of users with disabilities. These requirements not only consist of users abilities, but also users assistive technologies and the delivery context. In order to ascertain interoperability with other software components, user requirements are specified taking advantage of the extensibility of the W3C CC/PP recommendation and other feature-specification vocabularies. An evaluation tool capable of understanding these specifications generates evaluation reports that are tailored to the users individual needs. Quantitative accessibility measures resulting from personalized evaluation reports can be used to improve the web browsing experience for users with disabilities, such as through adaptive navigation support and by sorting the results of search engines according to users personal requirements. In addition, developers benefit from personalized evaluations when developing websites for specific audiences.

Technology for supporting web information search and learning in Sign Language

Sign Languages (SL) are underrepresented in the digital world, which contributes to the digital divide for the Deaf Community. In this paper, our goal is twofold: (1) to review the implications of current SL generation technologies for two key user web tasks, information search and learning and (2) to propose a taxonomy of the technical and functional dimensions for categorizing those technologies. The review reveals that although contents can currently be portrayed in SL by means of videos of human signers or avatars, the debate about how bilingual (text and SL) versus SL-only websites affect signers comprehension of hypertext content emerges as an unresolved issue in need of further empirical research. The taxonomy highlights that videos of human signers are ecological but require a high-cost group of experts to perform text to SL translations, video editing and web uploading. Avatar technology, generally associated with automatic text-SL translators, reduces bandwidth requirements and human resources but it lacks reliability. The insights gained through this review may enable designers, educators or users to select the technology that best suits their goals.

Evaluating web accessibility for specific mobile devices

This paper presents a tool for evaluating web accessibility for mobile devices regardless their software, hardware or user agent characteristics. Taking the mobileOK Basic tests by the W3C as a basis, these tests are extended so that device characteristics can be considered in the evaluation process. A sound tool that takes into account these extended tests has been developed. Device features of a given device are retrieved from heterogeneous device description repositories and CC/PP based profiles are automatically generated. Based on these profiles, evaluation queries are dynamically created obtaining device-tailored evaluation reports. Finally, in order to demonstrate the feasibility of the tool, a case study has been conducted concluding that the tool reduces the number of false positives and false negatives.

Including Heterogeneous Web Accessibility Guidelines in the Development Process

The use of web applications has extremely increased in the last few years. However, some groups of users may experience difficulties when accessing them. Many different sets of accessibility guidelines have been developed in order to improve the quality of web interfaces. Some of them are of general purpose whereas others are specific for user, application or access device characteristics. The existing amount of heterogeneous accessibility guidelines makes it difficult to find, select and handle them in the development process. This paper proposes a flexible framework which facilitates and promotes the web accessibility awareness during all the development process. The basis of this framework is the Unified Guidelines Language (UGL), a uniform guidelines specification language developed as a result of a comprehensive study of different sets of guidelines. The main components of the framework are the guidelines management tool and the flexible evaluation module. Therefore, sharing, extending and searching for adequate accessibility guidelines as well as evaluating web accessibility according to different sets of guidelines become simpler tasks.

Enriching web information scent for blind users

Link annotation with the accessibility level of the target Web page is an adaptive navigation support technique aimed at increasing blind users orientation in Web sites. In this work, the accessibility level of a page is measured by exploiting data from evaluation reports produced by two automatic assessment tools. These tools support evaluation of accessibility and usability guideline-sets. As a result, links are annotated with a score that indicates the conformance of the target Web page to blind user accessibility and usability guidelines. A user test with 16 users was conducted in order to observe the strategies they followed when links were annotated with these scores. With annotated links, the navigation paradigm changed from sequential to browsing randomly through the subset of those links with high scores. Even if there was not a general agreement on the correspondence between scores and user perception of accessibility, users found annotations helpful when browsing through links related to a given topic.

Transition of accessibility evaluation tools to new standards

While automatic tools are not intended to replace human judgement they are crucial in order to develop accessible web sites. The release of WCAG 2.0 entails that the existing plethora of accessibility review tools will have to be updated. This paper presents an evaluation framework for making the transition from WCAG 1.0 to WCAG 2.0 in a less painful way. A framework is thus proposed that allows developers to create new guidelines, and update or reuse the existing ones. A case study to test its feasibility has been carried out by incorporating WCAG 2.0 guidelines into the framework. The results are satisfactory, since 55% of the automatic and 16% of the semi-automatic ones could be expressed using the framework. Therefore, it is demonstrated that even if the framework does not fully support the transition process, at least it makes it less burdensome. Moreover, by analyzing WCAG 2.0 we have learnt how to extend the existing tools in order to provide greater coverage and thus increase their effectiveness.

Accessibility guidelines management framework

Due to the extensive amount of information regarding web accessibility developed in recent years, developers find difficulties for creating accessible web applications. Accessibility knowledge management tools can facilitate this task. However, existing tools do not provide enough support to all the activities of the development process. In this sense, developers have to use diverse tools focused on different stages and they are also required to search for accessibility information from different sources. The aim of this paper is to present a framework for managing accessibility guidelines. It serves as a central repository where developers can search for accessibility guidelines, define new guidelines, and share them with other developers and evaluating them automatically. Therefore, this framework facilitates developers tasks as it gives support to several activities of different stages throughout the development process.

Quantitative assessment of mobile web guidelines conformance

Conformance metrics for the mobile web can play a crucial role as far as engineering mobile websites are concerned, especially if they are automatically obtained. In this way, developers can have an idea in numeric terms of how suitable their developments are for mobile devices. However, there are a plethora of devices with their own particular features (screen size, formats support, etc.) that restrict a unified automatic assessment process. This paper proposes a tool-supported method for device-tailored assessment in terms of conformance with Mobile Web Best Practices 1.0, including the definition of five quantitative metrics for automatically measuring mobile web conformance: Navigability, Page layout, Page definition, User input and Overall score. The behaviour of these metrics was analysed for different devices and different web paradigms, both mobile web pages and their equivalent desktop pages. As expected, the results show that mobile web pages on more capable devices score higher. In addition, 20 users took part in an experiment aimed at discovering how conformance-based scores relate to usability dimensions. The results demonstrate that automatic scoring approaches strongly correlate with usability scores obtained by direct observation, such as task completion time and user satisfaction. This correlation is even stronger for the device-tailored assessment than the one that assumes a general profile for all devices. For instance, results show a strong negative correlation between Overall score and task completion time: ρ (9)xa0=xa0−0.81, (pxa0<xa00.05) for the generalist approach and ρ (9)xa0=xa0−0.88 for the device-tailored one, entailing that mobile web guidelines and the metrics based on their conformance capture usability aspects. This result challenges the widely accepted belief that conformance to guidelines does not imply more usable web pages, at least for web accessibility conformance.

Interdependence between technical web accessibility and usability: its influence on web quality models

Quality assurance is one of the most significant issues web engineering has to deal with. It is crucial to define adequate quality models in order to determine the most significant properties for quality evaluation of websites. Usability should be one of those properties as it bears on efficiency, effectiveness and user satisfaction. Moreover, it has been demonstrated to be a key property for users in recent European Commissions benchmark studies on quality and usage of public e-services. Web accessibility is also a significant property that websites have to fulfil in order to ensure equal access for all people in the Information Society. Therefore, both accessibility and usability should be included in such quality models. This paper presents an empirical study carried out with the aim of analysing the relationship between these two properties. The results show that the provision of technical web accessibility does not intrinsically guarantee web usability. Actually, other non-accessibility metrics such as the number of images, links and words of the web home page were better predictors of the users effectiveness, efficiency and satisfaction.