Karsten Tolle

Querying the Semantic Web with RQL

Real-scale Semantic Web applications, such as Knowledge Portals and E-Marketplaces, require the management of voluminous repositories of resource metadata. The Resource Description Framework (RDF) enables the creation and exchange of metadata as any other Web data. Although large volumes of RDF descriptions are already appearing, sufficiently expressive declarative query languages for RDF are still missing. We propose RQL, a new query language adapting the functionality of semistructured or XML query languages to the peculiarities of RDF but also extending this functionality in order to uniformly query both RDF descriptions and schemas. RQL is a typed language, following a functional approach a la OQL and relies on a formal graph model that permits the interpretation of superimposed resource descriptions created using one or more RDF schemas. We illustrate the syntax, semantics and type system of RQL and report on the performance of RSSDB, our persistent RDF Store, for storing and querying voluminous RDF metadata.

RQL: A Functional Query Language for RDF

Although real-scale Semantic Web applications, such as Knowledge Portals and E-Marketplaces, require the management of voluminous resource metadata, sufficiently expressive declarative languages for metadata created according to the W3C RDF/S standard1 are still missing. In answer to this need, we have designed a typed, functional query language, called RQL, whose novelty lies in its ability to smoothly combine schema and data querying. The purpose of this chapter is to present RQL’s formal data model and type system and illustrate its expressiveness by means of exemplary queries. RQL’s formal foundations capture the RDF/S modeling primitives and provide a well-founded semantics for a declarative query language involving recursion and functional composition over complex description graphs.

Managing RDF Metadata for Community Webs

The need for descriptive information, i.e., metadata, about Web resources has been recognized in several application contexts (e.g., digital libraries, portals). The Resource Description Framework (RDF) aims at facilitating the creation and exchange of metadata, as directed labeled graphs serialized in XML. In particular, the definition of schema vocabularies enables the interpretation of semistructured RDF descriptions using taxonomies of node and edge labels. In this paper, we propose (i) a formal model capturing RDF schema constructs; (ii) a declarative query language featuring generalized path expressions for taxonomies of labels (iii) a metadata management architecture for efficient storage and querying of RDF descriptions and schemas.

Building and evaluating nonobvious user profiles for visitors of Web sites

Building profiles of registered users of a Web site, as in case of a portal, is of importance if it goes beyond collecting the obvious information the user is willing to give at the time of registration. The starting point of this work is the assumption that a community of users is registered on a Web site and that for each user a profile is built. Such a profile contains two parts of data: one obvious, given directly by the user and one less obvious, inferred by the users behavior during his visits on the site. This paper presents ideas on how to build a user profile based on nonobvious information and takes into account various factors influencing in its development. Special emphases are paid on feedback mechanism and several methods of measuring its results.

The Design of Gugubarra 2.0: A Tool for Building and Managing Profiles of Web Users

We have introduced the concept of non-obvious user profiles (NOPs) to capture the hypothetical interest of Web users. In this paper we present the design principles and rules of our Gugubarra engine, which is a tool to calculate and visualize these non-obvious user profiles

The Gugubarra Project: Building and Evaluating User Profiles for Visitors of Web Sites

In this paper we will report the work currently being doing one the Gugubarra project. The project aims at building tools for better management of communities of Web visitors

Setting Up a Big Data Project: Challenges, Opportunities, Technologies and Optimization

In the first part of this chapter we illustrate how a big data project can be set up and optimized. We explain the general value of big data analytics for the enterprise and how value can be derived by analyzing big data. We go on to introduce the characteristics of big data projects and how such projects can be set up, optimized and managed. Two exemplary real word use cases of big data projects are described at the end of the first part. To be able to choose the optimal big data tools for given requirements, the relevant technologies for handling big data are outlined in the second part of this chapter. This part includes technologies such as NoSQL and NewSQL systems, in-memory databases, analytical platforms and Hadoop based solutions. Finally, the chapter is concluded with an overview over big data benchmarks that allow for performance optimization and evaluation of big data technologies. Especially with the new big data applications, there are requirements that make the platforms more complex and more heterogeneous. The relevant benchmarks designed for big data technologies are categorized in the last part.

Agent-based services for information portals

Web portals have a huge importance on todays Internet. Their purpose is to serve as an entry point to information on the Web, by proposing search and classification related services. The usefulness of a Web portal depends directly on the quality of service it offers. This paper presents the SIMAT architecture which exploits a backbone of machines running a secure mobile agent platform to improve quality of service. The agents are programmed to reduce the latency of information retrieval and to support the personalization and security of information search requests.

Performance and Architecture Modeling of Interoperability System for SME’s

SMEs’ needs to have sufficient information system functionality for affordable price were the main reason for development of business integration. Enterprise Service Bus (ESB) development and technology creation helped to better fulfill modern needs of SMEs. One of ESB variants – Application Bus for InteroperabiLITy In enlarged Europe SMEs (ABILITIES) – is described in this paper. Problems of creation, architecture and performance issues of such interoperability infrastructure are discussed. Colored Petri Net model for performance evaluation of such infrastructure is presented and evaluated.

Tailored Data Science Education Using Gamification

The interest to become a data scientist or related professions in data science domain is rapidly growing. To meet such a demand, we propose a novel educational service that aims to provide a tailored learning paths for data science. Our target user is one who aims to be an expert in data science. Our approach is to analyze the background of the practitioner and match the learning units. A critical feature is that we use gamification to reinforce the practitioner engagement. We believe that our work provides a practical guideline for those who wants to learn data science.