Location-dependent applications are becoming very popular in mobile environments. To improve system performance and facilitate disconnection, caching is crucial to such applications. In this paper, a semantic caching scheme is used to access location dependent data in mobile computing. We first develop a mobility model to represent the moving behaviors of mobile users and formally define location dependent queries. We then investigate query processing and cache management strategies. The performance of the semantic caching scheme and its replacement strategy FAR is evaluated through a simulation study. Our results show that semantic caching is more flexible and effective for use in LDD applications than page caching, whose performance is quite sensitive to the database physical organization. We also notice that the semantic cache replacement strategy FAR, which utilizes the semantic locality in terms of locations, performs robustly under different kinds of workloads.

http://people.cs.aau.dk/~simas/teaching/map_download/p210-ren.pdf

Using semantic caching to manage location dependent data in mobile computing

Location-dependent information services have great promise for mobile and pervasive computing environments. They can provide local and nonlocal news, weather, and traffic reports as well as directory services. Before they can be implemented on a large scale, however, several research issues must be addressed.

/pdf/data-management-in-location-dependent-information-services-tz66o1ihrc.pdf

Data management in location-dependent information services

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 location-dependent queries are defined and classified, and different query processing approaches are reviewed and compared.

https://webdiis.unizar.es/~silarri/PUBLICATIONS/acmSurvLDQP09.pdf

Location-dependent query processing: Where we are and where we are heading

Mobile ad hoc networks (MANET) are becoming an integral part of the ubiquitous computing and communication environment, providing new infrastructure for multimedia applications such as video phone, multimedia-on-demand, and others. In order to access multimedia information in MANET, Quality of Service (QoS) needs to be considered, such as high success rate to access multimedia data, bounded end-to-end delay, and others. In this paper, we present a data accessibility service for a group of mobile users to access desired data with high success rate. This accessibility service is only possible if we utilize advanced data advertising, lookup and replication services, as well as a novel predictive location-based QoS routing protocol in an integrated fashion. Using cross-layer design, we illustrate how the QoS routing protocol assists data advertising, lookup and replication services to achieve high data access success rate. Simulation results have shown that our design is successful in a dynamic MANET.

Cross-Layer Design for Data Accessibility in Mobile Ad Hoc Networks

Mobile location-dependent information services (LDISs) have become increasingly popular in recent years. However, data caching strategies for LDISs have thus far received little attention. In this paper, we study the issues of cache invalidation and cache replacement for location-dependent data under a geometric location model. We introduce a new performance criterion, called caching efficiency, and propose a generic method for location-dependent cache invalidation strategies. In addition, two cache replacement policies, PA and PAID, are proposed. Unlike the conventional replacement policies, PA and PAID take into consideration the valid scope area of a data value. We conduct a series of simulation experiments to study the performance of the proposed caching schemes. The experimental results show that the proposed location-dependent invalidation scheme is very effective and the PA and PAID policies significantly outperform the conventional replacement policies.

/pdf/cache-invalidation-and-replacement-strategies-for-location-3kvxz66y85.pdf

Cache invalidation and replacement strategies for location-dependent data in mobile environments

Semantic caching is very attractive for use in distributed systems due to the reduced network traffic and the improved response time. It is particularly efficient for a mobile computing environment, where the bandwidth of wireless links is a major performance bottleneck. Previous work either does not provide a formal semantic caching model, or lacks efficient query processing strategies. This paper extends the existing research in three ways: formal definitions associated with semantic caching are presented, query processing strategies are investigated and, finally, the performance of the semantic cache model is examined through a detailed simulation study.

Semantic caching and query processing

Semantic caching is particularly attractive for use in a mobile computing environment due to its content-based reasoning ability tid the fact that only the required data (as opposed to a file or pages of data) is transmitted over the wireless link. In this paper we propose a cluster based approach to manage a semantic cache, aiming at examining and further making use of the semantic locality among queries in a workload. Cache replacement performance using this technique is shown to outperform that of an LRU scheme where only temporal locality is considered.

Qun Ren

Papers

Using semantic caching to manage location dependent data in mobile computing

Semantic caching and query processing

Using clustering for effective management of a semantic cache in mobile computing