Creating Applications for Real-Time Collaboration with XMPP and Android on Mobile Devices

Introduction

There is already a multitude of collaborative applications available in mobile environments. Although they share a good amount of common functionality, most of them are built from scratch, or are tailored to a specific device platform using proprietary libraries. An open and customizable environment for mobile collaborative applications is still missing. To set up a generic environment for mobile collaboration support, the selection of the right set of underlying protocols is of high importance. Based on the protocols for collaboration the foundations for interoperability, scalability, portability and performance are created.

In earlier work (Springer et al., 2008) we introduced the Mobilis reference architecture as a service-oriented approach to support developers of mobile collaborative applications with a framework covering all the different aspects and layers of such applications. This comprises the device operating system, basic communication and context services, a service environment with commonly used functionality as well as the applications at the application layer. As can be seen in Figure 1, each of these four layers comprises a distinguished set of individual services. The functionality of the services at the Mobilis service layer will be described later in this chapter.

Figure 1.

Mobilis reference architecture

The Mobilis reference architecture already provides a good guideline for developers of mobile collaborative applications. It served already as a basis for the development of a set of applications adopting diverse collaboration functionality:

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  MobilisFunFlags: So-called fun flags can be tagged to locations at a map to notify other users of the application about cool places. Images and text notes can be attached to these places.

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  MobilisGuide: Tourists travelling together can create and join closed groups and are able to be aware of the other group members visualized as icons on a map-based view. They can interact by selecting icons of group members on the map, for instance to chat with each other or contact one another directly.

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  MobilisBuddy: Users get an alert if friends from social networks such as Facebook are in proximity (for instance if the distance is less than 100 meters) and can locate them on a map or call them.

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  MobilisTrader: Users of this application offer products such as a used washing machine or mobile phone together with the location of the product. Other users may insert requests for products. If request and offer matches within a pre-defined distance, both users get an alert and may contact each other.

These activities have been mainly carried out to drive the identification of appropriate services at the Mobilis service level which can be reused in different applications. The implementation of the various applications also enriched our experiences with the service platform. During the prototype development we also tested different target platforms. As described in (Springer et al., 2008), we implemented the MobilisGuide application for the three different platforms Java ME, Java SE, and Android. Furthermore, we tried different alternatives to realize the basic connectivity encapsulated in the Basic Services layer such as NaradaBrokering (Pallickara & Fox, 2003), Google App Engine (Google, 2009), and the eXtensible Messaging and Presence Protocol (XMPP) (XMPP, 2009).