Fona: Quantitative Metric to Measure Focus Navigation on Rich Internet Applications

The Web 2.0 brought new requirements to the architecture of web systems. Web applications’ interfaces are becoming more and more interactive. However, these changes are severely impacting how disabled users interact through assistive technologies with the web. In order to deploy an accessible web application, developers can use WAI-ARIA to design an accessible web application, which manually implements focus and keyboard navigation mechanisms. This article presents a quantitative metric, named Fona, which measures how the Focus Navigation WAI-ARIA requirement has been implemented on the web. Fona counts JavaScript mouse event listeners, HTML elements with role attributes, and TabIndex attributes in the DOM structure of webpages. Fona’s evaluation approach provides a narrow analysis of one single accessibility requirement. But it enables monitoring this accessibility requirement in a large number of webpages. This monitoring activity might be used to give insights about how Focus Navigation and ARIA requirements have been considered by web development teams. Fona is validated comparing the results of a set of WAI-ARIA conformant implementations and a set of webpages formed by Alexa’s 349 top most popular websites. The analysis of Fona’s value for Alexa’s websites highlights that many websites still lack the implementation of Focus Navigation through their JavaScript interactive content.