Ivana Podnar

Mobile push: delivering content to mobile users

The increasing popularity of information services that rely on content delivery in mobile environments motivates the need for a mobile push service - an efficient and flexible content dissemination service that targets mobile users. We analyze the features of a mobile push service by investigating representative usage scenarios and propose an architecture for mobile content delivery systems. The architecture is based on the publish/subscribe (P/S) paradigm which supports many-to-many interaction of loosely-coupled entities. We define the set of services that need to collaborate with the P/S infrastructure to address the dynamics of mobile environments.

Scalable Peer-to-Peer Web Retrieval with Highly Discriminative Keys

The suitability of peer-to-peer (P2P) approaches for full-text Web retrieval has recently been questioned because of the claimed unacceptable bandwidth consumption induced by retrieval from very large document collections. In this contribution we formalize a novel indexing/retrieval model that achieves high performance, cost-efficient retrieval by indexing with highly discriminative keys (HDKs) stored in a distributed global index maintained in a structured P2P network. HDKs correspond to carefully selected terms and term sets appearing in a small number of collection documents. We provide a theoretical analysis of the scalability of our retrieval model and report experimental results obtained with our HDK-based P2P retrieval engine. These results show that, despite increased indexing costs, the total traffic generated with the HDK approach is significantly smaller than the one obtained with distributed single-term indexing strategies. Furthermore, our experiments show that the retrieval performance obtained with a random set of real queries is comparable to the one of centralized, single-term solution using the best state-of-the-art BM25 relevance computation scheme. Finally, our scalability analysis demonstrates that the HDK approach can scale to large networks of peers indexing Web-size document collections, thus opening the way towards viable, truly-decentralized Web retrieval.

ALVIS peers: a scalable full-text peer-to-peer retrieval engine

We present Alvis peers, a full-text P2P retrieval engine designed to offer retrieval performance comparable to centralized solutions while scaling to a very large number of peers. It is the result of our research efforts within the project Alvis1 European FP 6 STREP project ALVIS, http://www.alvis.info/ that aims at building a truly-distributed semantic search engine. To cope with problem of unscalable bandwidth consumption in the P2P network, the engine implements a novel retrieval model that indexes highly-discriminative keys (HDKs)---terms and term sets appearing in a limited number of collection documents. Our prototype is a fully-functional retrieval engine built over a structured P2P network. It includes a component for HDK based indexing and retrieval, and a distributed content-based ranking module. Such an integrated system represents a substantial contribution to the design and development of realistic P2P retrieval systems.

A peer-to-peer architecture for information retrieval across digital library collections

Peer-to-peer networks have been identified as promising architectural concept for developing search scenarios across digital library collections. Digital libraries typically offer sophisticated search over their local content, however, search methods involving a network of such stand-alone components are currently quite limited. We present an architecture for highly-efficient search over digital library collections based on structured P2P networks. As the standard single-term indexing strategy faces significant scalability limitations in distributed environments, we propose a novel indexing strategy–key-based indexing. The keys are term sets that appear in a restricted number of collection documents. Thus, they are discriminative with respect to the global document collection, and ensure scalable search costs. Moreover, key-based indexing computes posting list joins during indexing time, which significantly improves query performance. As search efficient solutions usually imply costly indexing procedures, we present experimental results that show acceptable indexing costs while the retrieval performance is comparable to the standard centralized solutions with TF-IDF ranking.

A heuristic approach to wavelength assignment in all-optical networks

The paper presents an application of genetic algorithms to wavelength assignment in all-optical networks with wavelength division multiplexing (WDM). Two approaches, the shortest path routing and optimized routing are considered. The assignment results for a case study, a core part of the European Optical Network, are presented.

Software maintenance process analysis using discrete-event simulation

The competitive pressure and high costs of software maintenance force many IT organizations to carefully analyze and redesign their maintenance process. Identifying the changes that can remedy process deficiencies is not an easy task. Moreover, considerable risk is associated with implementing the proposed changes, since inadequate process design may cause a significant financial loss. The authors investigate the potential of simulation for analyzing and improving software maintenance processes. We present a simple, decision tree based model, suitable for software maintenance process simulation. The purpose of the model is to evaluate alternative process strategies and designs from a customer perspective. We apply the model to investigate deficiencies of the real software maintenance process and present a simulation experiment that examines an actual process design. Finally, we discuss the usability of simulation modeling for comparing and evaluating alternative process strategies in a real software process environment.

A business and domain model for information commerce

The expansion of the Internet and its use in business and commerce has created a number of new business opportunities and a need for their supporting models. One of these opportunities may be classified as information commerce (i-commerce), a special case of electronic commerce (e-commerce) focused on the purchase and sale of information as a commodity. I-commerce may also be viewed as a special case of the trading of intangible goods. In this paper, we present a business and domain model for the emerging field of i-commerce. The model, called CIP (Customer-Intermediary-Provider), describes an information marketplace, which is a virtual environment in which buyers and sellers of information may trade information products. The purpose of the model is to clarify the issues involved in i-commerce, to identify architectural requirements of i-commerce systems and to identify the new services that are needed to support such architectures on the Internet. Such models are necessary for understanding and classifying the rapidly increasing number of information and service providers on the Internet. Indeed, the CIP model may be used to describe the functions and services of many existing and emerging Web-based services.

SDL Based Approach to Software Process Modeling

The paper presents a Specification and Description Language (SDL) based approach to software process modeling. A brief review of other process modeling languages is given and the advantages of the ITU-T standardized SDL for formal model development are outline. Further on, it is shown how software process entities are modeled using SDL. Software maintenance process performed in a large telecommunications company is used as a case study. The software maintenance practice is first described informally, followed by a formal SDL software maintence model. Finally, the SDL model simulation and verification results are presented, and an overall assessment of SDL applicability for software process modeling is discussed.

Opportunities from Open Source Search

Internet search has a strong business model that permits a free service to users, so it is difficult to see why, if at all, there should be open source offerings as well. This paper first discusses open source search, and a rationale for the computer science community at large to get involved. Because there is no shortage of core open source components for at least some of the tasks involved, the Alvis Consortium is building infrastructure for open source search engines using peer-to-peer and subject specific technology as its core, based on this rationale. We view open source search as a rich future playground in which information extraction and retrieval components can be used and intelligent agents can operate.

An application of heuristic search techniques in telecommunication system design

Two heuristic search techniques, genetic algorithm and simulated annealing, were applied in searching for optimal solution of wavelength assignment problem in all-optical transmission network with wavelength division multiplex. The assignment results were compared for a case study-a core part of the European Optical Network.