P.M.E. De Bra

Information retrieval in the World-Wide Web: making client-based searching feasible

Abstract Finding specific information in the World-Wide Web (WWW, or Web for short) is becoming increasingly difficult, because of the rapid growth of the Web and because of the diversity of the information offered through the Web. Hypertext in general is ill-suited for information retrieval as it is designed for stepwise exploration. To help readers find specific information quickly, specific overview documents are often included into the hypertext. Hypertext systems often provide simple searching tools such as full text search or title search, that mostly ignore the “hyper-structure” formed by the links. In the WWW, finding information is further complicated by its distributed nature. Navigation, often via overview documents, still is the predominant method of finding ones way around the Web. Several searching tools have been developed, basically in two types: • A gateway, offering (limited) search operations on small or large parts of the WWW, using a pre-compiled database. The database is often built by an automated Web scanner (a “robot”). • A client-based search tool that does automated navigation, thereby working more or less like a browsing user, but much faster and following an optimized strategy. This paper highlights the properties and implementation of a client-based search tool called the “ fish-search ” algorithm, and compares it to other approaches. The fish-search, implemented on top of Mosaic for X, offers an open-ended selection of search criteria. Client-based searching has some definite drawbacks: slow speed and high network resource consumption. The paper shows how combining the fish search with a cache greatly reduces these problems. The “ Lagoon ” cache program is presented. Caches can call each other, currently only to further reduce network traffic. By moving the algorithm into the cache program, the calculation of the answer to a search request can be distributed among the caching servers.

A taxonomy of web agents

We propose a taxonomy of Web agents, which encompasses agents that provide a text-based interface to, for example, information retrieval services as well as avatar-embodied guides that help visitors to navigate in virtual environments. Our taxonomy must be regarded as an instrument to delineate targets for research and the realization of prototype applications that demonstrate the usefulness of agent-based intelligence on the Web. In addition, we deploy our agent-taxonomy to establish the implications particular target applications have with respect to software architecture and computational resources.

Tailoring Feedback in Online Assessment: Influence of Learning Styles on the Feedback Preferences and Elaborated Feedback Effectiveness

Design of feedback is a critical issue of online assessment development within Web-based Learning Systems (WBLSs). This paper examines the potential possibilities of tailoring the feedback that is presented to a student as a result of his/her preferences and responses to questions of an online test with respect to the individual learning styles (LS). The paper briefly reviews the main types of feedback that can be presented during online assessment and discusses the challenges in authoring and tailoring of feedback in WBLSs. We report the results of some recent experiments organized as online assessment of students through multiple-choice quizzes in which students were able to request different kinds of feedback for the answered questions. The experimental results have confirmed that LS have a significant influence on (1) the feedback preferences (with regard to response certitude and correctness) of students and (2) the effectiveness of elaborated feedback (EF), i.e. improving studentspsila performance during the test.

Discovery service for user models in a multi-application context

In order to efficiently manage information on the Web it becomes crucial to provide personalization not only within single systems, but across various Web applications. Interoperability of user models, on both syntactic and semantic level, emerges as a vital issue in order to achieve seamless personalization across different user-adaptive systems. In this paper we discuss the architecture of a broker-based discovery service for user models (BD-SUM), which allows applications to discover and invoke semantically described user models, in a multi-application context.

Retrieval of volatile database output through hypermedia applications

This paper reports on research on the generation of hypermedia (Web) applications for querying multimedia databases. We have proposed a heuristic algorithm for generating navigational structures for multimedia database output, based on ideas from RMM. Here we discuss two extensions to our approach. The first extension concerns in more depth the generation of navigation for volatile database output. The semantics of the data are used to produce a navigational structure for the hypermedia presentation, while by adding elements to the query syntax we allow the user to influence this. The second extension deals with the automatic generation of a presentation for the multimedia database output. While many of the presentation issues can be settled at design time by the designer of the application, a number of issues should be tackled at query time. These issues concern the presentation of records and their relationships with other records.

Adapting SME Learning Environments for Adaptivity

There is a genuine demand for personalization and guidance in learning systems, as well as in general commercial learning systems for the WWW, and further, for the new, emerging Semantic Web. Some isolated attempts towards adaptation are being made without fully responding to this demand. However, systematic frameworks for adaptive content and behavior description are already available in the research on Adaptive Hypermedia (AH). Here we present a novel application of an Adaptive Hypermedia Authoring framework and its principles towards extending an existing SME authoring environment for e-learning, as well as some initial evaluation results.

Transforming functional database schemes to relational representations

Semantic database models have become a popular tool for designing database schemes, despite the lack of an exact and efficient way to transform these schemes into (relational) database schemes for which efficient implementations exist and are widely available. This paper presents a precise and linear-time algorithm for transforming functional database schemes into relational ones.