Tap: an app framework for dynamically composable mobile systems

As smartphones and tablets have become ubiquitous, there is a growing demand for apps that can enable users to collaboratively use multiple mobile systems. We present Tap, a framework that makes it easy for users to dynamically compose collections of mobile systems and developers to write apps that make use of those impromptu collections. Tap users control the composition by simply tapping systems together for discovery and authentication. The physical interaction mimics and supports ephemeral user interactions without the need for tediously exchanging user contact information such as phone numbers or email addresses. Tapping triggers a simple NFC-based mechanism to exchange connectivity information and security credentials that works across heterogeneous networks and requires no user accounts or cloud infrastructure support. Tap makes it possible for apps to use existing mobile platform APIs across multiple mobile systems by virtualizing data sources so that local and remote data sources can be combined together upon tapping. Virtualized data sources can be hardware or software features, including media, clipboard, calendar events, and devices such as cameras and microphones. Leveraging existing mobile platform APIs makes it easy for developers to write apps that use hardware and software features across dynamically composed collections of mobile systems. We have implemented a Tap prototype that allows apps to make use of both unmodified Android and iOS systems. We have modified and implemented various apps using Tap to demonstrate that it is easy to use and can enable apps to provide powerful new functionality by leveraging multiple mobile systems. Our results show that Tap has good performance, even for high-bandwidth features, and is user and developer friendly.