RDF is increasingly being used to represent metadata. RDF Site Summary (RSS) is an application of RDF on the Web that has considerably grown in popularity. However, the way RSS systems operate today does not scale well. In this paper we introduce G-ToPSS, a scalable publish/subscribe system for selective information dissemination. G-ToPSS is particularly well suited for applications that deal with largevolume content distribution from diverse sources. RSS is an instance of the content distribution problem. G-ToPSS allows use of ontology as a way to provide additional information about the data. Furthermore, in this paper we show how G-ToPSS can support RDFS class taxonomies. We have implemented and experimentally evaluated G-ToPSS and we provide results in the paper demonstrating its scalability compared to alternatives.

Abstract—Applications involving the dissemination of information directly relevant to humans (e.g., service advertising, news spreading, environmental alerts) often rely on publish-subscribe, in which the network delivers a published message only to the nodes whose subscribed interests match it. In principle, publishsubscribe is particularly useful in mobile environments, since it minimizes the coupling among communication parties. However, to the best of our knowledge, none of the (few) works that tackled publish-subscribe in mobile environments has yet addressed intermittently-connected human networks. Socially-related people tend to be co-located quite regularly. This characteristic can be exploited to drive forwarding decisions in the interest-based routing layer supporting the publish-subscribe network, yielding not only improved performance but also the ability to overcome high rates of mobility and long-lasting disconnections. In this paper we propose SocialCast, a routing framework for publish-subscribe that exploits predictions based on metrics of social interaction (e.g., patterns of movements among communities) to identify the best information carriers. We highlight the principles underlying our protocol, illustrate its operation, and evaluate its performance using a mobility model based on a social network validated with real human mobility traces. The evaluation shows that prediction of colocation and node mobility allow for maintaining a very high and steady event delivery with low overhead and latency, despite the variation in density, number of replicas per message or speed. Index Terms— I.

The decoupling of producers and consumers in the publish/subscribe paradigm lends itself well to the support of mobile users who roam about the environment with intermittent network connectivity. This paper presents the first quantitative evaluation of publisher mobility in a distributed publish/subscribe system. Our results indicate that publisher mobility breaks a fundamental assumption of publish/subscribe systems and has a significant performance impact. We formalize publisher mobility algorithms for a distributed publish/subscribe system, and develop and evaluate optimizations to the mobile publisher algorithms. 1

With the increasing popularity of wireless communication networks and mobile handheld devices, there is a pressing need to extend traditional distributed applications to mobile environments. In this paper, we propose a novel solution to support mobile clients in publish/subscribe systems. The key of our solution is the two-phase handover (2PH) protocol. In comparison with existing solutions, our solution can guarantee the exactly-once and ordered event delivery to mobile clients with very low cost, and does not require mobile clients to wait for a long time to get the undelivered events upon reconnection. Concurrent movement of multiple clients is considered and mechanisms are provided to resolve the possible conflicts during the handover processes. 1.

The event paradigm and publish/subscribe systems allow clients to asynchronously receive information that matches their interests. The requirements of mobile computing present new challenges pertaining to event delivery that need to be solved. In this paper, we formally examine several state transfer protocols for different pub/sub topologies. The new results of this paper are the cost functions for both subscriber and publisher mobility, and investigation and formulation of completeness of subscriptions and advertisements. The results show that rendezvous points are good for pub/sub mobility, handovers in incomplete topologies are more costly than in complete, and the brokers involved with mobility have no way of detecting completeness based on local information alone.

Mobile devices have received much research interest in recent years. Mobility raises new issues such as more dynamic context, limited computing resources, and frequent disconnections. These handle these issues, we propose a middleware, called 3DMA, which introduces three requirements, 1) distribution, 2) decoupling and 3) decomposition.

Abstract. We present a selective neighbor caching approach for supporting mobility in publish/subscribe networks. According to the approach, a mobile’s subscriptions are transmitted to a subset of brokers that are neighbors of the current broker that the mobile is connected to. Our key contribution is the definition of a target cost function and an intelligent procedure for selecting the subset of neighbors. The advantage of our proposal is that it reduces the buffering costs, since not all neighbor brokers cache items, while still obtaining the gains of proactive caching, by caching items in a subset of neighbor brokers that a mobile has a high probability to connect to. 1

Abstract—The publish/subscribe (pub/sub for short) paradigm is used to deliver events from a source to interested clients in an asynchronous way. Recently, extending a pub/sub system in wireless networks has become a promising topic. However, most existing works focus on pub/sub systems in infrastructured wireless networks. To adapt pub/sub systems to mobile ad hoc networks, we propose DRIP, a dynamic Voronoi region-based pub/sub protocol. In our design, the network is dynamically divided into several Voronoi regions after choosing proper nodes as broker nodes. Each broker node is used to collect subscriptions and detected events, as well as efficiently notify subscribers with matched events in its Voronoi region. Other nodes join their nearest broker nodes to submit subscriptions, publish events, and wait for notifications of their requested events. Broker nodes cooperate with each other for sharing subscriptions and useful events. Our proposal includes two major components: a Voronoi regions construction protocol, and a delivery mechanism that implements the pub/sub paradigm. The effectiveness of DRIP is demonstrated through comprehensive simulation studies. I.

The continuous development of wireless networks and mobile devices has motivated an intense research in mobile data services. Some of these services provide the user with context-aware information. Specifically, location-based services and location-dependent queries have attracted a lot of interest. In this article, the existing literature in the field of location-dependent query processing is reviewed. The technological context (mobile computing) and support middleware (such as moving object databases and data stream technology) are described, location-based services and locationdependent queries are defined and classified, and different query processing approaches are reviewed and compared.

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