Model-Driven Development for Accessible Mobile Apps on Android

The market for apps and mobile software is on the rise and this goes hand in hand with the number of apps in the stores, which has recently hit 3 million available apps (see https://www:statista:com/statistics/266210/). Due to this development, the natural user interaction of smartphones plays a crucial role. People with disabilities benefit from the increasing digital technology in general, but only if it is accessible. However, apps are often not accessible for people with disabilities since touch screens and visual representation very often overlook their needs. According to the UN Convention on the Rights of Persons with Disabilities around 650 million people of the worlds population are handicapped. Within the European Union (EU) about 80 million people are affected by disabilities prompting the union to enact the Directive (EU) 2016/2102 which requests that websites and mobile applications of public sector bodies are accessible for all. Reviewing top apps in the Android store shows that even very popular apps such as WhatsApp, Messenger and Instagram have accessibility problems, i.e. contrast of texts and images, missing object descriptions or too small touch target sizes, preventing users with disabilities from having equal access to those apps (see Chapter1). The thesis at hand presents an innovative approach, supporting the implementation of accessibility in the design and development process of mobile applications from the very beginning. We propose a model-driven approach for better integration and addressing accessibility requirements in the design and development process. To prove this concept, developers receive a prototype-tool - called Accapto (Accessible App Tool) - to transfer an interaction prototype to a formal model. The abstract definition describes screens, user interface elements and interaction workflows in a domain-specific description language. The model is transformed into a working app prototype for the Android platform. In the generation process, the app is created with proper platform-specific accessibility support and enhanced with additional supportive features and provides guidance to the developer to efficiently and effectively implement accessibility. In the course of the thesis, the level of accessibility of apps implemented with Accapto is evaluated against Web Content Accessibility Guidelines (WCAG 2.0) and also tested with users with disabilities. In particular, the new development tool is analyzed in an empirical study with 50 involved developers. In two test groups, the model-driven development approach using Accapto is compared with the standard development method. The results show a significant improvement in terms of accessibility for the model-driven development approach. Therefore the thesis proves that model-driven approaches have a high potential to significantly improving app accessibility from the beginning and helps developers to raise their awareness for the needs of special user groups.submitted by Dipl.-Ing. Elmar KrainzUniversität Linz, Dissertation, 2018OeBB(VLID)267998