The thesis deals with three document retrieval models based on logic: the Boolean model,the fuzzy model and the Van Rijsbergen model.In Chapter 1, the author presents the purpose of the thesis. This is to give the logical foundationof the models, to describe them and to examine them critically. In Chapter 2, some importantnotions in document retrieval are presented. Chapter 3 is devoted to the Boolean model, Chapter4 to the fuzzy model and Chapter 5 to the Van Rijsbergen model.These three chapters are organized in the same way. First, the logical foundation of the modelis given.

The aim with this thesis came out of a strong interest for Passage Retrieval. Our intention has not been to evaluate an IR-system. Instead our goal has been to analyze the result of indexing documents and their passages. We have been studying the weights of the different terms in the different indices, in comparison with other parameters like frequency, normalized frequency and the inversed document frequency. Further more we have been looking at how the weights are spread using for instance the standard deviation.

The purpose of this study is to examine the difference between three query strategies with respect to retrieval effectiveness. The thesis aims at examining how two types of noun phrases containing a modifier to the head word, which is a noun affect the retrieval performance with regard to recall and precision. The noun phrases in the thesis are of two types: 1) noun phrases containing a modifier to the head word (which is a noun) and which are not dictionary phrases (NF) and 2) dictionary phrases. Both types of noun phrases in this thesis contain at least two words. The queries were executed in Query Performance Analyser, QPA, containing the InQuery system and a sub collection of TREC-Uta documents with its topics.

Automatic query expansion has long been studied in information retrieval research as a technique that deals with the fundamental issue of word mismatch between query and document. The purpose of this thesis is to compare the retrieval effectiveness of different strategies for automatic query expansion. The strategies are based on local analysis of the corpus and use statistical information from the local document set to extract terms that suppose to adapt themselves to each individual search and therefore appear to be searchonyms to the index terms. The strategies compared are: association clusters, metric cluster and scalar cluster. Baseline queries of 24 topics are expanded using terms from the different clusters and searches are made.

TPB, The Swedish Library of Talking Books and Braille, has requested a study to investigate the organization and content of a possible future Swedish web portal for users with reading disabilities. The aim of this thesis is to conduct such a study, with an emphasis on knowledge organization. The main aspects studied are formal description, representation, search and retrieval, document retrieval, and additionally also aspects related to content. The following questions are answered in this thesis: - How are web portals, online databases and Internet libraries for users with reading disabilities constructed, from an organization of knowledge point of view? - How can these solutions for knowledge organization be incorporated into a possible Swedish web portal? - With regards to content, which additional aspects are present in the studied web portals, online databases and Internet libraries? The questions are addressed through a detailed study of ten web portals, online databases and Internet libraries from Nordic and Anglo-American parts of the world.

The aim of this thesis is to describe passage retrieval (PR), with basis in results from various empirical experiments, and to critically investigate different approaches in PR. The main questions to be answered in the thesis are: (1) What characterizes PR? (2) What approaches have been proposed? (3) How well do the approaches work in experimental information retrieval (IR)? PR is a research topic in information retrieval, which instead of retrieving the fulltext of documents, that can lead to information overload for the user, tries to retrieve the most relevant passages in the documents. This technique was investigated studying a number of central articles in the research field. PR can be divided into three different types of approaches based on the segmentation of the documents.

This thesis deals with one of the main questions within information science: The question about controlled and uncontrolled vocabulary and which of the two that are most effective when it comes to retrieve relevant information from electronic databases. The method used here is literature studies. I have described and examined five empirical studies which has been done in purpose to compare the effectiveness in retrieval with controlled and uncontrolled vocabulary, in the way they are used in retrieval of information in databases. The studies I have examined have also used recall and precision as a value to measure the effectiveness of retrieval. The studies which I have chosen is also limited to deal only with studies that have been done in bibliographic databases.

The aim of this thesis is to describe and critically investigate eight different evaluations of the retrieval effectiveness of webbased search engines. The questions to be answered in this investigation are: - What kind of relevance judgements have been used? - Which criteria have been used when judging the relevance of a document? - Which measures have been used? - How many queries have been used? - How were the queries constructed? - What document cut-off value has been used? - Has hypothes testing been applied? - What kind of webbased search engines have been included in the evaluations? The study showed that although the evaluations investigate the same phenomena, they are very different from each other in certain aspects. Generally the study showed that precision is the preferred measure in comparison to recall in the chosen evaluation even though all the included evaluations have constructed unique formulas for calculating precision. Some attempts to measure relative recall have been performed but they all suffer from different defects.

This Master?s thesis examines different retrieval strategies used in cross-language information retrieval (CLIR). The aim was to investigate if there were any differences between baseline queries and translated queries in retrieval effectiveness; how the retrieval effectiveness was affected by query structuring and if the results differed between different languages. The languages used in this study were Swedish, English and Finnish. 30 topics from the TrecUta collection were translated into Swedish and Finnish.

The purpose of this essay is to examine how high school students (age 13 to 19) search for information on the web and in databases. Furthermore, it aims to look into how critical of sources they are. The questions asked was: how the students search for information in digital media? Which kind of sources do the students use? How they evaluate the information they find? Do they get any education in information retrieval and source evaluation? To answer these questions students were interviewed in groups about their information retrieval behavior. Furthermore two school librarians were interviewed about their experience of the students? information retrieval.During the interviews it was clear that the students had received quite sparse instructions on the subjects of information retrieval and criticism of the sources.

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This paper is a comparing study of the retrieval effectiveness of the search engines Google, Google Scholar and Scirus. The aim is to find out how good they are at retrieving relevant academic material in the research-field of Library and Information science. The thirty search questions where based on actual information needs collected from exams within the field of Library and Information Science. This method was used to prevent that none of the search engines were given an advantage because of construction of the information needs. The first twenty retrieved documents on the retrieval lists are examined for academic content and relevance.

The aim of this master thesis is to evaluate the performance of the content-based image retrieval system ImBrowse from a semantic point of view. Evaluation of retrieval performance is a problem in content-based image retrieval (CBIR). There are many different methods for measuring the performance of content-based image retrieval systems, but no common way for performing the evaluation. The main focus is on image retrieval regarding the extraction of the visual features in the image, from three semantic levels. The thesis tries to elucidate the semantic gap, which is the problem when the systems extraction of the visual features from the image and the user?s interpretation of that same information do not correspond.

E-mail lämpas som marknadsföringskanal endast i förhållande till varans eller tjänstens relationsförväntan, som kunden förknippar varan ellertjänsten med. Denna relationsförväntan utgörs av faktorer såsom pris, tidigare kunskap om produkten och produktsegment..

Romanization as a method in the bibliographic environment makes retrieval difficult in many aspects. The object of this thesis is to illustrate the importance and the possibility to include non-Roman script in the records of the library catalogue. The questions at issue are about the consequences of romanization, the technical requirements for implementing non-Roman script, and bibliographical resources that have been developed during the last 20 years. The thesis is based on a literature study and correspondence with people who are familiar with the subject. The thesis points out that Romanization causes information to be distorted in various ways and is inconsistent with the requirements of exactitude in bibliographic control.