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.

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..

Image indexing research today is either conducted on a visual attribute level or on a higher semantic level, forming a semantic gap between the two. There is much to gain if research progress from the two fields is combined. Image retrieval using access points in both visual and semantic significations could improve retrieval and bridge the gap. In social media today, images are often the primary communication agent and the number of images on the web is increasing in an uncontrolled way. New and efficient ways to index and retrieve the images are needed.The purpose of this study is to examine if emotions could be a semantic access point for Image retrieval and if folksonomy indexing is useful when searching for images that represent emotions.

This essay explores to what extent the Swedish language version of Google Images meets the usability requirements of average everyday users. Previously published studies on user behaviour and users? interface and search option preferences define the usability requirements, which are matched against Google Images? actual interface and search options. The retrieval method of Google Images is also briefly discussed, and users? opinions about Google Images too, as they come across in the previously published user studies.The findings are that Google Images lack some of the things that users ask for, but it still seems to be the most used image search engine among average internet users and more appreciated than other search engines.

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 essay is a survey of thirteen user studies performed in the field of Image retrieval. The purpose is to try to distinguish principles that should be kept in mind when wanting to make image databases available for a wide and varied group of users. The essay tries to answer two questions, namely: Are there any results in accordance among the different studies? What in the user studies should be considered when it comes to how content description, interface and functions for searching can be designed when creating systems for Image retrieval? Each study is first reviewed on its own, and then a comparative analysis of all the studies is carried out. Derived from the result of this analysis, the conclusion is presented in the form of a row of suggestions to which aspects are to be suitably included in the design of image databases.

The purpose of this thesis is to evaluate 7 different search strategies for content-based Image retrieval with respect to retrieval effectiveness. The strategies are based on different levels of resolution implemented by the Haar transformation. The result of the study shows an improvement in both mean average precision and mean recall in strategies based on lower levels of resolution..

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 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?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 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 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.

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.

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 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..