Manos Spanoudakis

Extensible platform for location based services provisioning

Location based services can be considered as the most rapidly expanding field of the mobile communications sector. The proliferation of the mobile/wireless internet, the constantly increasing use of handheld, mobile devices and position tracking technologies and the emergence of mobile computing, prepared the grounds for the introduction of this new type of services with impressively large application domain and use range. Prompted by the avalanche of technology advances in the aforementioned areas in this paper we present a generic platform for delivering location based services (LBS). The platform features a modular architecture, which can be easily extended with additional functionality. The paper focuses on the technical specifications, the design and the prototype implementation of the platforms kernel, which is responsible for coordinating communication with various pluggable components in order to provide the full range of operations involved in the LBS delivery chain (i.e., from initial deployment to invocation, execution and delivery of results). Issues such as scalability, efficiency, openness, portability and security are also considered in the design of the platform.

Using Web Services for supporting the users of wireless devices

The Web Service paradigm is currently considered as the most promising and rapidly evolving technology for developing applications in open, distributed and heterogeneous environments. The proliferation of this new technology has coincided with significant advances in the hardware and software capabilities of wireless devices. The combination of the two worlds (i.e. making wireless devices capable of providing and consuming Web Services) is considered of major importance to the computing industry for the forthcoming years. This paper describes two scenarios of using Web Services in wireless devices, identifies their advantages and supporting technologies. A reference architecture for the use of Web Services in the wireless world is proposed. Finally, the results of the performance evaluation of an experimental setup are presented.

Using XML and related standards to support Location Based Services

Location Based Services can be considered as the most rapidly expanding field of the mobile communications sector. The proliferation of the mobile/wireless Internet, the constantly increasing use of handheld, mobile devices and positioning technologies and the emergence of mobile computing, prepared the grounds for the introduction of this new type of services with impressively large application domain and use range. The combination of position fixing mechanisms with location-dependent, georgraphical information, can offer truly customized personal communication services through the mobile phone or other type of devices. Web Services have emerged as a set of open standards and gained a lot of momentum during the recent past. Many software vendors are announcing Web Service initiatives and adoption in their products. Many organizations are involved in the refinement of Web Service standards. Moreover, XML has become the de facto standard for data interchange on the Web and its emergence is having an enormous impact on Web development. Motivated by the technology advances in the aforementioned areas in this paper we discuss the exploitation of Web Services and XML to build a generic platform for delivering Location Based Services (LBS) to the nomadic user.

A generic framework for Location-Based Services (LBS) provisioning

Location Based Services can be considered as one of the most rapidly expanding fields of the mobile communications sector, with an impressively large application range. The proliferation of mobile/wireless Internet and mobile computing, and the constantly increasing use of handheld, mobile devices and position tracking technologies prepared the grounds for the introduction of this new type of services. The combination of position fixing mechanisms with location-dependent, geographical information, can offer truly customized personal communication services through the mobile phone or other type of devices. Prompted by the avalanche of technology advances in the aforementioned areas in this paper we present an integrated platform for delivering Location Based Services (LBS). The platform covers the full life cycle of a LBS starting from the specification of the service, covering issues like the deployment and maintenance of services, the service invocation and the final delivery of the produced results to the invoking user. A prototype implementation of the discussed platform was developed and used to perform a series of trial services, with the purpose of demonstrating the pursued functionality.

Open Middleware Architecture for the LBS Domain

The combination of position fixing mechanisms with location-dependent, geographical information can offer truly customized personal communication services through the mobile phone or other types of devices. Prompted by the avalanche of technology advances in the aforementioned areas, in this article we present a generic framework for delivering location-based services (LBS). The framework is capable of providing the full functionality required for delivering LBS, starting from the specification of the service, and covering issues like the deployment and maintenance of services, the service invocation and the final delivery of the produced results to the calling user. The main focus of the article is on the technical specification, the design, and the functionality of the framework. However, with the purpose of assessing the proposed architecture, a prototype implementation based on the discussed specifications was built and its performance was evaluated using a series of pilot services.

On the Use of Optimal Stopping Theory for Cache Consistency Checks

Serving the most updated version of a resource with minimal networking overhead is always a challenge for WWW Caching, especially, for weak consistency algorithms such as the widely adopted Adaptive Time-to-Live (ATTL). We adopt the Optimal Stopping Theory (OST) and, specifically, the Odds-algorithm, to enable the caching server to accurately handle the object refreshing and the stale delivery problem. Simulation results show that the proposed OST-based algorithm outperforms the conventional ATTL.

On the use of optimal stopping theory for improving cache consistency

Serving the most updated version of a resource with minimal networking overhead is always a challenge for WWW Caching; especially, for weak consistency algorithms such as the widely adopted Adaptive Time-to-Live (ATTL). We adopt the Optimal Stopping Theory (OST) and, specifically, the Odds-algorithm, to enable the caching server to accurately handle the object refreshing and the stale delivery problem. Simulation results show that the proposed OST-based algorithm outperforms the conventional ATTL.

Adaptive partial CDN replication

Content Distribution Networks are a very important part of todays Internet and the Web. They enable the scalable provision of content and yield significant saving for the information provides (the clients of the CDN). In this paper we propose a scheme that tries to optimize the use of disk space in the CDN. The basic idea involves the partial replication of the contents of a web site. Site objects are transferred to the CDN in bundles. The site partitioning technique that produces bundles can be based on the site structure or the popularity of the site contents. We propose two schemes for site partitioning: the static partitioning and a technique based on Markov graphs (mostly intended for Web prefetching). We simulated the discussed schemes using extensive traces taken from the site of our department. Our findings are very promising for the proposed schemes.