ANEL: robust mobile network programming using a declarative language.

The dynamics of mobile networks make it difficult for mobile apps to deliver a seamless user experience. In particular, intermittent connections and weak signals pose challenges for app developers. While recent network libraries have simplified network programming, much expert knowledge is still required. However, most mobile app developers are relative novices and tend to assume a reliable network connection, paying little attention to handling network errors in programming until users complain and leave bad reviews. We argue that the difficulty of avoiding such software defects can be mitigated through an annotation language that allows developers to declaratively state desired and actual properties of the application, largely without reference to fault-tolerant concepts, much less implementation. A pre-compiler can process these annotations, replacing calls to standard networking libraries with customized calls to a specialized library that enhances the reliability. This paper presents ANEL, a declarative language and middleware for Android that enables non-experts. We demonstrate the expressiveness and practicability of ANEL annotation through case studies and usability studies on real-world networked mobile apps. We also show that the ANEL middleware introduces negligible runtime performance overhead.