Accessibility and usability in the context of human-computer interaction

The themes of usability and accessibility are gaining more and more importance worldwide. Usability refers to the ease of using products according to users’ needs and requirements, whereas accessibility refers to the possibility of employing certain products or technologies regardless of potential disabilities of users, also in relation to technical constraints inherent in the products themselves. In various multimodal contexts, several guidelines and “good-design” rules for usable and accessible sites have been defined internationally, with some countries having passed laws aimed at enforcing their adoption. Starting from web-related considerations, we provide an overview of the problems which should be tackled when creating usable and accessible interfaces which include captions and subtitles , and focus on the theories that offer possible solutions to such problems.