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We propose a new approach to collaborative filtering in mobile tourist information systems based on spatio-temporal proximity in social contexts. The approach is motivated by a survey of festival visitors confirming that similarities of interests extends beyond events defining specific social contexts. We show how opportunistic information sharing in mobile ad-hoc networks can be used to realise decentralised collaborative filtering appropriate for mobile environments and show its equivalence to existing centralised approaches.

Web 2.0 users may publish a rich variety of personal data to a number of sites by uploading personal desktop data or actually creating it on the Web 2.0 site. We present a framework and tools that address the resulting problems of information fragmentation and fragility by providing users with fine grain control over the processes of publishing and importing Web 2.0 data. IntroductionAn increasing amount of personal data is being published on Web 2.0 sites such as Facebook and Flickr as well as various forms of discussion forums and blogs. These sites provide easy-to-use solutions for sharing data with friends and user communities, and consumers of that data can contribute to the body of information through actions such as tagging, linking and writing comments. Sometimes, Web 2.0 sites also take over the primary role of managing a user's personal data by providing simple tools for creating, storing, organising and retrieving data, even when users are on the move.Desktop applications for multimedia processing such as Adobe Photoshop Lightroom provide tools to support the publishing process. There is also an increasing number of tools to support cross publishing, meaning that information posted on one site is published automatically to another. For example, WordPress allows information published on Twitter to be automatically published as a blog article and vice versa. Although such tools facilitate the publishing process, they are only available for certain types of data and applications. Further, since it is now typical for active users of Web 2.0 sites to publish data to many different sites, they need to learn to use a variety of publishing tools, some of which require manual activation while others are fully automated.Another problem is the fragility of information managed solely by Web 2.0 sites since many of these sites are considered to have an uncertain future. For example, the expenses incurred by YouTube far exceed their advertisement revenues which has led to speculation about its future [1]. It may therefore be desirable to import data from Web 2.0 sites into desktop applications to ensure offline and/or long-term access.

Most object databases offer little or no support for eventbased programming over and above wha t is provided in the programming language. Consequently, functionality offered by traditional database triggers and event-condition-action (ECA) rules has to be coded in each application. We believe that a notion of triggers should be offered by object databases to facilitate application development and a clear separation of concerns. We present a general and flexible event model tha t unifies concepts from programming languages and database triggers. We describe an implementation of the model and how it can support the requirements of a rich variety of applications.

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