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 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.

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.

This master thesis deals with events, dynamics and problems of mediated information seeking within the context of a new information service called "Book a librarian". The study, based on a survey and interviews both in academic and public libraries and participant observations in academic libraries, has its theoretical base in the cognitive theory of Information retrieval interaction. The cognitive view is used to throw light upon the need of an ongoing dialogue during the session in order to detect the information needs of the user and to conduct a successful retrieval of information. The communicative interaction is seen as threepart interaction between the intermediary, the user and the information system, where the current cognitive states of all three participants are involved. The study shows that the cognitive obstacles for a successful mediation and Information retrieval are mostly connected to participants current knowledge of the subject and of the retrieval techniques.

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 aim of this Masters thesis is, partly, to examine the information needs of lesbians: what discernable information needs they have, how they seek information and which information sources they use. The purpose is also to examine what part fiction plays regarding the information needs mentioned above and how fiction indexing could improve retrieval. The study is conducted through ten qualitative interviews with lesbians as well as through textual analysis. The theoretical framework includes queer theory and theory concerning information needs and uses. The results indicate that lesbians have evident information needs that mostly concern identity.

The purpose of this paper is to examine the three main translation methods used in experimental Cross-language Information retrieval CLIR research today, namely translation using either machine-readable dictionaries, machine translation systems or corpus-based methods. Working notes from research groups participating in the Text Retrieval Conference TREC and the Cross-Language Evaluation Forum CLEF between 1997 and 2000 have provided the main source material used to discuss the possible advantages and drawbacks that each method presents. It appears that all three approaches have their pros and cons, and because the different researchers tend to favour their own chosen method, it is not possible to establish a "winner approach" to CLIR translation by studying the working notes alone. One should remember however that the present interest in cross-language-applications of Information retrieval has arisen as late as in the 1990s, and thus the research is yet in its early stages. The methods discussed in this paper may well be improved, or perhaps replaced by others in the future..

The purpose of this bachelor thesis is to find out how information seeking habits and experiences of people in different generations affects their expectations on Information retrieval systems like OPAC. Two OPACs are used, one web-OPAC and one mobile-OPAC. The following questions are asked: how can theories about information seeking behaviors explain why and in which way one seeks information? In which way does information seeking behaviors and habits affect the experience of OPAC? Which differences and/or similarities can be found between the web-OPAC and the mobile-OPAC? How does generational aspects affect experiences and preferences in an information seeking context? The theoretical framework of the thesis is Information retrieval with several models about information-seeking/searching needs and behaviors. The empirical data contains interviews with nine people in different generations and protocols about two different OPACs.

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.

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.

The web has made an incredible amount of unorganized information available to anyone. There are search engines that help us structuring the information, but it is still difficult to find what you search for on the web. The purpose of this master's thesis is to investigate whether the already existing techniques for automatic indexing are suited for the new Information retrieval context on the web and how the choice to support these techniques, or not, affects the search results. This is examined through a literature study on automatic indexing and other related concepts, such as Information retrieval and information searching on the web in order to get a theoretical frame to the work and by an observation of the search engine HotBot to approach the purpose of the thesis. The observation is carried out by searching HotBot's database and investigating the search results in order to try to identify patterns that can reveal something about how HotBot's automatic indexing is done.

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.

As the information society becomes increasingly flooded with digital images, the need for efficient image retrieval systems increases as well. To handle the vast amounts of data involved, the indexing process needs to be run automatically, using content-based descriptors extracted directly from the digital image, such as colour composition, shape and texture features. These content-based image retrieval systems are often slow and cumbersome, and can appear confusing to an ordinary user who does not understand the underlying mechanisms. One step towards more efficient and user-friendly retrieval systems might be to adjust the weight placed on various descriptors depending on which image category is being searched for. The results of this thesis show that certain categories of digital images would benefit from having extra weight assigned to colour, texture or shape features when searching for images of that category..

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.