Yannis Panagis

Techniques to support Web Service selection and consumption with QoS characteristics

This work proposes a Web Service (WS) discovery model in which the functional and non-functional requirements are taken into account during service discovery. The proposed infrastructure includes a set of services and tools to support an integrated WS discovery and selection solution. A mechanism is introduced that supports three different functional policies. It is able to take advantage of quality information located into a Web Service description language description file that might be located in a proprietary universal description, discovery and integration registry server or in an independent URL. Moreover, it implements a database supported WS intermediary (Broker) that it is also possible to store quality of service (QoS) information for WSs. A selection module is also presented that delivers the WS that maximizes the value of QoS characteristics among others with the same functionality. An experimental prototype is presented and evaluated in the scenario of air ticket issuing WS selection.

Category ranking for personalized search

Despite the effectiveness of search engines, the persistently increasing amount of web data continuously obscures the search task. Efforts have thus concentrated on personalized search that takes account of user preferences. A new concept is introduced towards this direction; search based on ranking of local set of categories that comprise a user search profile. New algorithms are presented that utilize web page categories to personalize search results. Series of user-based experiments show that the proposed solutions are efficient. Finally, we extend the application of our techniques in the design of topic-focused crawlers, which can be considered an alternative personalized search.

Efficient and adaptive discovery techniques of Web Services handling large data sets

Attempts have been made concerning the search and finding of a Web Service based on keywords and descriptions. However, no work has been done concerning the efficient selection of the appropriate Web Service instance in terms of quality and performance factors at the moment of the Web Service consumption attempt. Such factors may include execution time and response time. The proposed approach adaptively selects the most efficient WS among possible different alternatives with real-time, optimized and countable factors-parameters. Implementation issues and case study experiments are presented along with the corresponding results. Additionally, an optimal selection algorithm for series of Web Services requests is proposed. Finally, conclusions and future steps are discussed.

Web Service discovery based on Quality of Service

Late developments in Web Service discovery approaches mainly focus on the incorporation of the QoS concept in the selection process. In this paper, we present a generalized design and implementation of a QoS enabled Web Service discovery mechanism. We describe a mechanism extending the propositions of [1] in a generalized environment that consists of dynamic groups/ categories of different Web Services. A UDDI search wrapper is introduced to facilitate the traditional WS discovery by taking into account QoS characteristics in transparent way. Our aim is the combination of the classic Web Service discovery, at design or execution time, with the benefit of QoS characteristics without affecting the existing UDDI search facilities. To evaluate the functionality, feasibility and effectiveness of the mechanism proposed, a number of experimental applications have been developed. All applications have been available for evaluation online in laboratory.

Efficient Algorithms for Handling Molecular Weighted Sequences

In this paper we introduce the Weighted Suffix Tree, an efficient data structure for computing string regularities in weighted sequences of molecular data. Molecular Weighted Sequences can model important biological processes such as the DNA Assembly Process or the DNA-Protein Binding Process. Thus pattern matching or identification of repeated patterns, in biological weighted sequences is a very important procedure in the translation of gene expression and regulation. We present time and space efficient algorithms for constructing the weighted suffix tree and some applications of the proposed data structure to problems taken from the Molecular Biology area such as pattern matching, repeats discovery, discovery of the longest common subsequence of two weighted sequences and computation of covers.

Optimisation mechanism for web search results using topic knowledge

Web searching - one of the most frequent activities in the internet community - is perhaps the most complicated one because of the abundant resulting information available. Users are often puzzled because of long results of ranking lists that are compiled without considering their individual preferences and needs. We present a mechanism in this work that reranks and groups search results on the users side according to his/her explicit and implicit choices. Furthermore, a caching strategy is introduced to minimise personalisation effect response time. A web environment prototype has been developed to exemplify the potentials of the proposed mechanism. User assessment has been conducted to verify the effectiveness of the mechanism. Results and feedbacks have been efficient and encouraging, respectively.

Web service workflow selection using system and network QoS constraints

Web services serve as a leading technology platform for web-based data-centric environments providing flexibility of loose coupling, message-based communication. Interest in more efficient web services selection strategies is rather requisite especially from the business process workflow perspective. We present several strategies to efficiently select a set of web services performing a workflow, fulfilling quality specifications at all workflow steps. The focus is on finding the best performing web service given a history of the execution times and current measured variation in operating system and network resource consumption. To assess their efficiency, we experimentally evaluate them and present comparative results, which strongly indicate that they can effectively reduce the overall workflow execution time in a web service-based workflow with QoS constraints. Approaches are presented for a number of workflows depending on their particular characteristics.

Discovering re-usable design solutions in web conceptual schemas: metrics and methodology

In the Internet era, the development of Web applications has impressively evolved and is characterized by a large degree of complexity. To this end, software community has proposed a variety of modeling methods and techniques. In this work, we provide a methodology and metrics for mining the conceptual schema of applications, to discover recurrent design solutions in an automatic manner. The mechanism is designed for models based on WebML, a modeling language for designing data-intensive applications. This approach, when applied in an applications conceptual schema, results in effective design solutions, as it facilitates reuse and consistency in the development and maintenance process. Furthermore, when applied to a large number of applications, it enables hypertext architects to identify templates for Web application frameworks for specific domains and to discover new design patterns extending the predefined set of patterns supported by WebML. Finally, we illustrate a validation scenario.

Personalization techniques for Web search results categorization

Generic Web search is designed to serve all users, independent of the individual needs and without any adaptation to personal requirements. We propose a novel technique that performs post-categorization to the results of popular search engines at the clients side. A user profile is built based on users choices from a category hierarchy (explicitly given requirements) and users search history (implicitly logged choices). Caching is utilized in order to provide improved responses. An experimental prototype has been implemented based on results coming from a popular search engine. The experimental results indicate strongly that the proposed mechanism is both effective and efficient.

e-souvenir appification: QoS web based media delivery for museum apps

The advent and recent proliferation of applications, created for smartphones and tablets, has altered the way users interact with information that is available online. Appification has been recently introduced to describe the rapidly widening shift from Web browsing to the usage of smartphone Apps for Internet-based information access and e-services consumption. In this paper, we present a solution that introduces e-souvenir (digital souvenir), extending the appification of e-shopping and shopping (non electronic) souvenirs while visiting cultural sights (e.g. museum, exhibitions etc). Instead of just buying a souvenir from a museum, the proposed smartphone App increases user involvement in order to personalize the App with his/her choices while sight-seeing and thus, such choices form an electronic souvenir: the e-souvenir. Additionally, our approach introduces intelligent Quality of Service (QoS) enabled features to the cultural smartphone App to improve user’s experience, while using it at cultural sights and points of interest. We facilitate efficient QoS-based media delivery to the e-souvenir solution in order to make it efficient to operate under heavy network traffic load and best-effort Internet-based connections. This is especially important to handle bottlenecks that occur, when tourists gather the most popular exhibits within the exhibition rooms, and when they visit the museum in groups (e.g. schools, cruises etc). The proposed solution is a tool for better understanding and appreciation of the cultural exhibits while being on site, and it serves as an electronic souvenir in the post-visit experience. We show how QoS assurance techniques enable efficient media delivery through smartphones to assist making the old fashioned shopping souvenirs to go online and become virtual. The proposed QoS enabled smartphone solution serves as a high quality digital souvenir after museums’ visits. This solution has already received warm feedback and encouraging comments by tourist and museum professionals.