The purpose of this paper is to compare the three search engines Web of Science, Google Scholar and MEDLINE in regards of recovery efficiency and the overlap of relevant documents when it comes to information searching for academic purposes. Furthermore, it raises the question whether freely available search engines and licensed search engines are interchangeable with each other. The empirical data in this study were collected through searches conducted in the three search engines Web of Science, Google Scholar and MEDLINE. Twenty search queries were used and the first twenty retrieved documents for each query were examined for relevance using previously designed criteria. The documents were scored by a binary relevancy scale and thereafter a precision value for each search engine was calculated.

The purpose of this thesis is to examine which factors influence librarians selection of electronic information sources, and to investigate whether librarians use of search strategies and search tactics changes depending on which information source they use. The electronic information sources are: online databases, Online Public Access Catalogues OPAC, World Wide Web, and CD-ROM databases. The theoretical framework is based on step 3 Select a source and step 4 Formulate a Query in Marchioninis information seeking model. The search strategies are divided into two categories: analytical and browsing strategies. In order to supplement the theoretical framework with empirical facts, 8 librarians were interviewed.

This thesis deals with query formulation in full text retrieval. The variables studied were query expansion and query structur[INS: e :INS , and the aim of the thesis is to study their co-effects on retrieval performance in a probabilistic system. The expansion was made with synonyms, and the structure by expressing facets and phrases. The study was performed using QPA, Query Performance Analyzer, which includes InQuery retrieval system and a sub-collection of TREC documents with its topics. The measurement used was precision at 11 DCV points.

This thesis examines the retrieval effectiveness of two Web search engines. The two search engines are chosen to represent two different types Google as a broad general search engine and Dogpile as a broad general metasearcher. Twenty queries have been used and the first twenty hits for each query were evaluated for relevance. The queries were invented by the authors, based upon their interests and information needs. They were expressed in a general manner, by using one or several keywords, in accordance with the simple search mode available for each search engine.

This thesis examines the effects of proximity operators and query expansion with synonyms on retrieval performance. The queries were expanded with synonyms and structured with proximity operators where the permitted distance between terms varied from 1 to 3. The expansion terms were selected from the online lexical reference system WordNet. Initial query terms were selected from 28 topics that contained compound words and were chosen on the basis of their expandibility. The English morphological analyser ENGTWOL was used for normalization of query terms.

The purpose of this thesis is to examine the performance of queries that are expanded by 1 inflections, 2 compound splitting and 3 inflections and compound splitting combined. For compound splitting, the morphological analyser SWETWOL was used. Queries were executed in the Query Performance Analyser, QPA, containing the InQuery system. Query terms were selected from 29 topics, all of whom containing at least one compound word. Both the queries and the documents were in Swedish.

The aim of this study was to compare the Query-by-Humming systems Midomi, Musicline and Tunebot regarding their retrieval effectiveness. The aim was to see if there were differences between the systems but also between the user groups common users, musicians and singers. Query-by-Humming system means that the user sings a tune that the system then use to find the right melody.To compare the systems and their users, queries where collected from the different user groups and replayed for the systems. Mean Reciprocal Rank and Friedman test was used to do the comparison.The results showed that the system did not achieve equivalent and that there were no difference between the user groups. The Mean Reciprocal Rank showed that the systems had very different retrieval effectiveness, where Midomi was the system with best result and Musicline with the lowest result..

The aim of this thesis is to contribute to increased knowledge concerning students? information seeking in an electronic environment. Using a qualitative approach; focus groups interviews, a total of nine nursing students were interviewed in two groups. The interviews were transcribed and analyzed with an analysis tool based upon Lucy Kuntz?s, Gary Marchionini?s and Carol C Kuhlthau?s models of the information seeking process.

The theoretical focus in this master is information retrieval (IR), and especially the part of IR that includes interactivity. This research is by some researchers called IIR. Our principal aim was to examine if search engines on the WWW are taking advantage of research results from IIR research. A way to do this is to look at the application of special features, in this case query expansion (QE) and relevance feedback (RF). Both these methods aim for a better matching of documents and the searchers information need.

This aim of this thesis is to measure the effect of the user interface in real searches on the Internet through a small experiment. Theories on web and search usability and psychological factors concerning usability were first explored. Then three interfaces were constructed, one "good" that followed usability guidelines and had multiple search functions, one "bad" that completely disobeyed those guidelines and had only a simple and small search field, and one "intermediate" interface that was a mix of the two. The search field was set to different sizes, with the shortest in the "bad" interface, a medium field in the "intermediate" interface and several long fields in the "good" interface. All three interfaces were then attached to the same web search engine, Altavista.

The aim of this thesis is to compare the effectivity of using a natural language and a controlled vocabulary when performing subject searches in the bibliographic database LISA Library and Information Science Abstracts. 20 topics were created and for each topic two searches were made, one by using a query formulated with natural language directed to the abstract field and the other one by using a query formulated with descriptors from the thesaurus in LISA directed to the descriptor field. The average relative recall amounted to 64,8% for the AB-queries and 54% for the DE-queries. Failure analysis showed that the majority of the relevant documents not retrieved by AB-queries could have been retrieved with other query terms, such as synonyms. In a natural language there are many different ways of expressing a topic, and this tends to have a negative effect on retrieval effectivity.

The Internet offers an abundance of information. This information is easy to access in technical terms, however it is difficult to find. At present there is a wide variety of search services to choose from. This master's thesis is about selecting the appropriate search service for a certain question. Are different types of services suitable for different types of questions, and if so, which services for which questions?To answer this, I have undertaken one theoretical and one empirical study.

The aim of this thesis is to examine how thesauri constructed with latent semantic indexing LSI are performing when used for query expansion. There is a well-known problem with synonymy in information retrieval and one solution to this problem is to use a thesaurus. In this thesis thesauri are created automatically to find statistically related words and not only synonyms. LSI is a method that uses singular value decomposition SVD to reduce dimensions in a matrix and find latent relationships between words. We constructed nine thesauri and used them for query expansion in a Swedish database, GP_HDINF.

The purpose of this thesis is to examine how academic librarians seek information for themselves and for others, and what differences exist. The terms self-generated and imposed information seeking is used to describe the two different types of information seeking. Step 2 ? define and understand the problem, step 3 ? choose a search system and step 4 ? formulate a query of Marchionini?s information-seeking model forms the basis of the theoretical framework, which is supplemented with Soergel and Katz. Qualitative interviews with eight academic librarians were conducted and analyzed in order to gather empirical facts.

The purpose of this thesis is to examine how academic librarians seek information for themselves and for others, and what differences exist. The terms self-generated and imposed information seeking is used to describe the two different types of information seeking. Step 2 ? define and understand the problem, step 3 ? choose a search system and step 4 ? formulate a query of Marchionini?s information-seeking model forms the basis of the theoretical framework, which is supplemented with Soergel and Katz. Qualitative interviews with eight academic librarians were conducted and analyzed in order to gather empirical facts.