Diese Datenbank enthält über 40.000 Dokumente zu Themen aus den Bereichen Formalerschließung – Inhaltserschließung – Information Retrieval.
© 2015 W. Gödert, TH Köln, Institut für Informationswissenschaft / Powered by litecat, BIS Oldenburg (Stand: 28. April 2022)
1Vakkari, P. ; Völske, M. ; Potthast, M. ; Hagen, M. ; Stein, B.: Predicting essay quality from search and writing behavior.
In: Journal of the Association for Information Science and Technology. 72(2021) no.7, S.839-852.
Abstract: Few studies have investigated how search behavior affects complex writing tasks. We analyze a dataset of 150 long essays whose authors searched the ClueWeb09 corpus for source material, while all querying, clicking, and writing activity was meticulously recorded. We model the effect of search and writing behavior on essay quality using path analysis. Since the boil-down and build-up writing strategies identified in previous research have been found to affect search behavior, we model each writing strategy separately. Our analysis shows that the search process contributes significantly to essay quality through both direct and mediated effects, while the author's writing strategy moderates this relationship. Our models explain 25-35% of the variation in essay quality through rather simple search and writing process characteristics alone, a fact that has implications on how search engines could personalize result pages for writing tasks. Authors' writing strategies and associated searching patterns differ, producing differences in essay quality. In a nutshell: essay quality improves if search and writing strategies harmonize-build-up writers benefit from focused, in-depth querying, while boil-down writers fare better with a broader and shallower querying strategy.
Inhalt: Vgl.: https://asistdl.onlinelibrary.wiley.com/doi/10.1002/asi.24451.
2Vakkari, P. ; Völske, M. ; Potthast, M. ; Hagen, M. ; Stein, B.: Modeling the usefulness of search results as measured by information use.
In: Information processing and management. 56(2019) no.3, S.879-894.
Abstract: The documents retrieved by a web search are useful if the information they contain contributes to some task or information need. To measure search result utility, studies have typically focused on perceived usefulness rather than on actual information use. We investigate the actual usefulness of search results-as indicated by their use as sources in an extensive writing task-and the factors that make a writer successful at retrieving useful sources. Our data comprise 150 essays written by 12 writers whose querying, clicking and writing activities were recorded. By tracking authors' text reuse behavior, we quantify the search results' contribution to the task more accurately than before. We model the overall utility of the search results retrieved throughout the writing process using path analysis, and compare a binary utility model (Reuse Events) to one that quantifies a degree of utility (Reuse Amount). The Reuse Events model has greater explanatory power (63% vs. 48%); in both models, the number of clicks is by far the strongest predictor of useful results-with ß-coefficients up to 0.7-while dwell time has a negative effect (ß between -0.14 and -0.21). As a conclusion, we propose a new measure of search result usefulness based on a source's contribution to an evolving text. Our findings are valid for tasks where text reuse is allowed, but also have implications on designing indicators of search result usefulness for general writing tasks.
Inhalt: Vgl.: https://doi.org/10.1016/j.ipm.2019.02.001.
3Wu, I.-C. ; Vakkari, P.: Effects of subject-oriented visualization tools on search by novices and intermediates.
In: Journal of the Association for Information Science and Technology. 69(2018) no.12, S.1428-1445.
Abstract: This study explores how user subject knowledge influences search task processes and outcomes, as well as how search behavior is influenced by subject-oriented information visualization (IV) tools. To enable integrated searches, the proposed WikiMap + integrates search functions and IV tools (i.e., a topic network and hierarchical topic tree) and gathers information from Wikipedia pages and Google Search results. To evaluate the effectiveness of the proposed interfaces, we design subject-oriented tasks and adopt extended evaluation measures. We recruited 48 novices and 48 knowledgeable users, that is, intermediates, for the evaluation. Our results show that novices using the proposed interface demonstrate better search performance than intermediates using Wikipedia. We therefore conclude that our tools help close the gap between novices and intermediates in information searches. The results also show that intermediates can take advantage of the search tool by leveraging the IV tools to browse subtopics, and formulate better queries with less effort. We conclude that embedding the IV and the search tools in the interface can result in different search behavior but improved task performance. We provide implications to design search systems to include IV features adapted to user levels of subject knowledge to help them achieve better task performance.
Themenfeld: Visualisierung ; Suchtaktik
4Mikkonen, A. ; Vakkari, P.: Reader characteristics, behavior, and success in fiction book search.
In: Journal of the Association for Information Science and Technology. 68(2017) no.9, S.2154-2165.
Abstract: We examined the search behaviors of diverse fiction readers in different search scenarios. The aim was to understand how fiction readers with varied reading preferences are selecting interesting novels in library catalogs. We conducted a controlled user study with 80 participants. Two reader groups were elicited according to similar reading preference patterns. The readers enjoyed the entertainment, escape, and comfort that reading as a pleasurable activity offered. The aesthetic readers valued the artistic and aesthetic pleasures, widening vocabulary, and ability to express oneself through fiction books. We compared the search queries and search actions between the 2 reader groups. Our results demonstrated that preference patterns were associated with readers' search behavior, that is, the number of viewed search result pages, opened book pages, dwell time on book pages, and the type of search queries. Based on the findings, we present 3 search tactics for fiction books in library catalogs: i) focused querying, ii) topical browsing, and iii) similarity-based tactic. The most popular search tactic in each search scenario was "focused querying" with known author in both reader groups.
Inhalt: Vgl.: http://onlinelibrary.wiley.com/doi/10.1002/asi.23843/full.
Themenfeld: Schöne Literatur
5Mikkonen, A. ; Vakkari, P.: Readers' interest criteria in fiction book search in library catalogs.
In: Journal of documentation. 72(2016) no.4, S.696-715.
Abstract: Purpose - The purpose of this paper is to investigate fiction readers' interest criteria when selecting novels in library catalogs for various search tasks. Design/methodology/approach - The data of the book selection behavior from 80 genuine fiction readers were collected using recorded interviews and conversations. The data were qualitatively analyzed. Reuter's categorization of the components of aesthetic relevance has contributed to the construction of interest dimensions. Findings - A five-dimension categorization of interest criteria is presented based on fiction readers' interpretations of the influential factors in fiction book selection in different search tasks. The findings revealed that readers apply the identified interest criteria in a flexible and multiphase way depending to the search task and the system used. The findings showed a context-related pattern in readers' fiction book selections. A combination of readers' search capacities, "behind the eyes" knowledge, affective factors and a well-functioning interaction with a system used results in a successful book selection. Originality/value - A five-dimension categorization of adult fiction readers' interest criteria was created based on their search behaviors in library catalogs. The results provide a systematic step toward a comprehensive understanding of readers' fiction book selection in digital environments.
Inhalt: Vgl.: http://www.emeraldinsight.com/doi/abs/10.1108/JDOC-11-2015-0142.
Themenfeld: Schöne Literatur
6Tuomaala, O. ; Järvelin, K. ; Vakkari, P.: Evolution of library and information science, 1965-2005 : content analysis of journal articles.
In: Journal of the Association for Information Science and Technology. 65(2014) no.7, S.1446-1462.
Abstract: This article first analyzes library and information science (LIS) research articles published in core LIS journals in 2005. It also examines the development of LIS from 1965 to 2005 in light of comparable data sets for 1965, 1985, and 2005. In both cases, the authors report (a) how the research articles are distributed by topic and (b) what approaches, research strategies, and methods were applied in the articles. In 2005, the largest research areas in LIS by this measure were information storage and retrieval, scientific communication, library and information-service activities, and information seeking. The same research areas constituted the quantitative core of LIS in the previous years since 1965. Information retrieval has been the most popular area of research over the years. The proportion of research on library and information-service activities decreased after 1985, but the popularity of information seeking and of scientific communication grew during the period studied. The viewpoint of research has shifted from library and information organizations to end users and development of systems for the latter. The proportion of empirical research strategies was high and rose over time, with the survey method being the single most important method. However, attention to evaluation and experiments increased considerably after 1985. Conceptual research strategies and system analysis, description, and design were quite popular, but declining. The most significant changes from 1965 to 2005 are the decreasing interest in library and information-service activities and the growth of research into information seeking and scientific communication.
7Wu, I.-C. ; Vakkari, P.: Supporting navigation in Wikipedia by information visualization : extended evaluation measures.
In: Journal of documentation. 70(2014) no.3, S.392-424.
Abstract: Purpose - The authors introduce two semantics-based navigation applications that facilitate information-seeking activities in internal link-based web sites in Wikipedia. These applications aim to help users find concepts within a topic and related articles on a given topic quickly and then gain topical knowledge from internal link-based encyclopedia web sites. The paper aims to discuss these issues. Design/methodology/approach - The WNavis application consists of three information visualization (IV) tools which are a topic network, a hierarchy topic tree and summaries for topics. The WikiMap application consists of a topic network. The goal of the topic network and topic tree tools is to help users to find the major concepts of a topic and identify relationships between these major concepts easily. In addition, in order to locate specific information and enable users to explore and read topic-related articles quickly, the topic tree and summaries for topics tools support users to gain topical knowledge quickly. The authors then apply the k-clique of cohesive indicator to analyze the sub topics of the seed query and find out the best clustering results via the cosine measure. The authors utilize four metrics, which are correctness, time cost, usage behaviors, and satisfaction, to evaluate the three interfaces. These metrics measure both the outputs and outcomes of applications. As a baseline system for evaluation the authors used a traditional Wikipedia interface. For the evaluation, the authors used an experimental user study with 30 participants. ; Findings - The results indicate that both WikiMap and WNavis supported users to identify concepts and their relations better compared to the baseline. In topical tasks WNavis over performed both WikiMap and the baseline system. Although there were no time differences in finding concepts or answering topical questions, the test systems provided users with a greater gain per time unit. The users of WNavis leaned on the hierarchy tree instead of other tools, whereas WikiMap users used the topic map. Research limitations/implications - The findings have implications for the design of IR support tools in knowledge-intensive web sites that help users to explore topics and concepts. Originality/value - The authors explored to what extent the use of each IV support tool contributed to successful exploration of topics in search tasks. The authors propose extended task-based evaluation measures to understand how each application provides useful context for users to accomplish the tasks and attain the search goals. That is, the authors not only evaluate the output of the search results, e.g. the number of relevant items retrieved, but also the outcome provided by the system for assisting users to attain the search goal.
8Vakkari, P. ; Huuskonen, S.: Search effort degrades search output but improves task outcome.
In: Journal of the American Society for Information Science and Technology. 63(2012) no.4, S.657-670.
Abstract: We analyzed how effort in searching is associated with search output and task outcome. In a field study, we examined how students' search effort for an assigned learning task was associated with precision and relative recall, and how this was associated to the quality of learning outcome. The study subjects were 41 medical students writing essays for a class in medicine. Searching in Medline was part of their assignment. The data comprised students' search logs in Medline, their assessment of the usefulness of references retrieved, a questionnaire concerning the search process, and evaluation scores of the essays given by the teachers. Pearson correlation was calculated for answering the research questions. Finally, a path model for predicting task outcome was built. We found that effort in the search process degraded precision but improved task outcome. There were two major mechanisms reducing precision while enhancing task outcome. Effort in expanding Medical Subject Heading (MeSH) terms within search sessions and effort in assessing and exploring documents in the result list between the sessions degraded precision, but led to better task outcome. Thus, human effort compensated bad retrieval results on the way to good task outcome. Findings suggest that traditional effectiveness measures in information retrieval should be complemented with evaluation measures for search process and outcome.
Themenfeld: Retrievalstudien ; Suchtaktik
9Numminen, P. ; Vakkari, P.: Question types in public libraries' digital reference service in Finland : comparing 1999 and 2006.
In: Journal of the American Society for Information Science and Technology. 60(2009) no.6, S.1249-1257.
Abstract: This study analyzes to which degree the question types addressed to a digital reference service run by a consortium of public libraries have changed between the Years 1999 and 2006. The data consist of representative samples of reference questions to a Finnish Ask a Librarian digital reference service in the years studied. Questions were classified based on a taxonomy refining earlier major taxonomies. The proportion of ready reference questions had increased from 33 to 45% whereas the proportion of subject-based research questions had decreased from 57 to 47%. Among the former, fact-finding questions had especially increased, and among the latter, topical search questions had decreased. These changes in the popularity of question types are likely related to the way people are searching on the Internet. It is concluded that the Internet has somewhat reduced the traditional role of public libraries in mediated topical searching.
Themenfeld: Internet ; Informationsdienstleistungen
Anwendungsfeld: Öffentliche Bibliotheken
10Vakkari, P.: Perceived influence of the use of electronic information resources on scholarly work and publication productivity.
In: Journal of the American Society for Information Science and Technology. 59(2008) no.4, S.602-612.
Abstract: This study explores how the use of electronic information resources has influenced scholars' opinion of their work, and how this is connected to their publication productivity. The data consist of a nationwide Web-based survey of the end-users of FinELib, the Finnish Electronic Library, at all universities in Finland. Scholars feel that the use of electronic literature has improved their work considerably in several ways. This influence can be differentiated into two dimensions. The first one is improved accessibility and availability of literature, and the second is more directly related to the content and quality of scholarly work. The perceived improved access is positively associated with the number of international publications produced, among doctoral students in particular. The more direct influence of e-resource use on the content of scholarly work is, however, not associated with publication productivity. The results seem to imply that investments in academic digital libraries are beneficial for the researchers and for the universities.
11Eerola, J. ; Vakkari, P.: How a general and a specific thesaurus cover expressions in patients' questions and physicians' answers.
In: Journal of documentation. 64(2008) no.1, S.131-142.
Abstract: Purpose - This paper sets out to examine the degree to which General Finnish Thesaurus (GFT) and FinMeSH cover various semantic expressions of medical concepts in patients' questions and physicians' answers concerning cardiovascular diseases. The former represents lay persons' information needs. Design/methodology/approach - A total of 50 question-answer pairs were collected in a medical web site. Concepts and their expressions (terms) with their semantic relations were identified in questions and answers. Findings - FinMeSH covered 65 per cent and GFT 41 per cent of all medical terms in texts. The expressions of patients and physicians matched better with FinMeSH than GFT regardless of the type of expression. The difference in favour of FinMeSH was typically about 25 per cent-units. Originality/value - The low fit with users' vocabularies makes GFT a poor tool for supporting searching, whereas the relatively high fit of FinMeSH suggests that it is a reasonable tool in assisting searching. Conclusions concerning the bridging of these two thesauri are discussed.
Objekt: General Finnish Thesaurus ; FinMeSH
12Huuskonen, S. ; Vakkari, P.: Students' search process and outcome in Medline in writing an essay for a class on evidence-based medicine.
In: Journal of documentation. 64(2008) no.2, S.287-303.
Abstract: Purpose - The aim of this study is to explore to which extent searching by medical students in Medline produces information items useful for writing an essay measured by precision and relative recall as perceived by the students, the proportion of cited items, and their utilization on four dimensions of the essay writing task evaluated by external assessors. It also aims to study interrelations of search process and outcome. Design/methodology/approach - The study subjects were 42 third year medical students attending a class on Diagnostic and therapy. Searching in Medline was a part of their assignment of essay writing. The data consist of students' printed logs of Medline searches, students' assessments of the usefulness of the references retrieved, a questionnaire concerning the search process, and evaluation scores of the essays given by the teachers of the class. Pearson correlation coefficients were calculated for answering the research questions. Findings - The paper finds that precision and relative recall were not associated with evaluation scores in three of the four dimensions assessed. Some of the process variables were associated with precision and with assessment scores in two of the four dimensions assessed. Citing rate was negatively associated with recall. It seems that precision and recall are only weakly, if at all, associated to the use of information in the documents retrieved for writing the essay. Precision and relative recall are not associated to the way information in the retrieved items is used for performing the task. Users evidently look for a sufficient number of documents containing enough information for progressing in their task. Precision and recall are not sufficient measures in evaluating IR systems, but they have to be completed by other measures indicating the impact of the system on users' task performance. Originality/value - The paper provides useful information on students' information search process.
13Talja, S. ; Vakkari, P. ; Fry, J. ; Wouters, P.: Impact of research cultures on the use of digital library resources.
In: Journal of the American Society for Information Science and Technology. 58(2007) no.11, S.1674-1685.
Abstract: Currently, there exists little evidence concerning how various characteristics of research cultures are associated with patterns of use of electronic library resources. The present study addresses this gap by exploring how research-group membership, across-fields scattering of literature, and degree of establishment of research area are related to patterns of digital library use. The analytic dimensions are derived from Richard Whitley's () theory of the social and intellectual organization of academic fields. The article represents a first attempt to operationalize Whitley's concepts in a large-scale study of e-resources use. The data used in the study were gathered in 2004 by the Finnish Electronic Library (FinElib) through a nationwide Web-based user questionnaire (N = 900). Membership in a research group significantly increased searching in journal databases, the importance of colleagues as sources of information about electronic articles and journals, and the use of alert services. A significant interaction effect was found between degree of across-fields scattering of relevant resources and degree of establishment of research fields. A high degree of across-fields scattering of relevant literature increased the number of journal databases used mainly in less established research areas whereas it influenced the use of journal databases less in established fields. This research contributes to our picture concerning the complex set of interacting factors influencing patterns of use of e-resources.
14Serola, S. ; Vakkari, P.: ¬The anticipated and assessed contribution of information types in references retrieved for preparing a research proposal.
In: Journal of the American Society for Information Science and Technology. 56(2005) no.4, S.373-381.
Abstract: This small-scale empirical study focuses an students' anticipated and assessed contribution of references retrieved during the preparation of research proposals. It explores how the expected contribution of types of information before searches differs from the assessed contribution of relevant references found by the types of information. Twenty-two psychology undergraduates searched the PsychINFO database for references at the initial and end stages of a seminar for preparing proposals. Data about their subject knowledge, search goals, and utility assessments were collected using several methods. They were asked to predict and assess the utility of information types provided by relevant references for the proposals. At the beginning of the process, they found fewer general types of information and more specific types of information than they expected. However, the students tended to accept references according to their expectations. By the end of the process, the expected importance of general information types declined and the importance of specific information types increased. At the end of the task, students became more proficient at recognizing the utility and topicality of references. They also became more critical in accepting found information to match their expectations.
15Vakkari, P. ; Järvelin, K.: Explanation in information seeking and retrieval.
In: New directions in cognitive information retrieval. Eds.: A. Spink, C. Cole. Dordrecht : Springer Netherland, 2005. S.113-138.
(The information retrieval series, vol. 19)
Abstract: Information Retrieval (IR) is a research area both within Computer Science and Information Science. It has by and large two communities: a Computer Science oriented experimental approach and a user-oriented Information Science approach with a Social Science background. The communities hold a critical stance towards each other (e.g., Ingwersen, 1996), the latter suspecting the realism of the former, and the former suspecting the usefulness of the latter. Within Information Science the study of information seeking (IS) also has a Social Science background. There is a lot of research in each of these particular areas of information seeking and retrieval (IS&R). However, the three communities do not really communicate with each other. Why is this, and could the relationships be otherwise? Do the communities in fact belong together? Or perhaps each community is better off forgetting about the existence of the other two? We feel that the relationships between the research areas have not been properly analyzed. One way to analyze the relationships is to examine what each research area is trying to find out: which phenomena are being explained and how. We believe that IS&R research would benefit from being analytic about its frameworks, models and theories, not just at the level of meta-theories, but also much more concretely at the level of study designs. Over the years there have been calls for more context in the study of IS&R. Work tasks as well as cultural activities/interests have been proposed as the proper context for information access. For example, Wersig (1973) conceptualized information needs from the tasks perspective. He argued that in order to learn about information needs and seeking, one needs to take into account the whole active professional role of the individuals being investigated. Byström and Järvelin (1995) analysed IS processes in the light of tasks of varying complexity. Ingwersen (1996) discussed the role of tasks and their descriptions and problematic situations from a cognitive perspective on IR. Most recently, Vakkari (2003) reviewed task-based IR and Järvelin and Ingwersen (2004) proposed the extension of IS&R research toward the task context. Therefore there is much support to the task context, but how should it be applied in IS&R?
16Vakkari, P. ; Sormunen, E.: ¬The influence of relevance levels an the effectiveness of interactive information retrieval.
In: Journal of the American Society for Information Science and Technology. 55(2004) no.11, S.963-969.
Abstract: In this paper, we focus an the effect of graded relevance an the results of interactive information retrieval (IR) experiments based an assigned search tasks in a test collection. A group of 26 subjects searched for four Text REtrieval Conference (TREC) topics using automatic and interactive query expansion based an relevance feedback. The TREC- and user-suggested pools of relevant documents were reassessed an a four-level relevance scale. The results show that the users could identify nearly all highly relevant documents and about half of the marginal ones. Users also selected a fair number of irrelevant documents for query expansion. The findings suggest that the effectiveness of query expansion is closely related to the searchers' success in retrieving and identifying highly relevant documents for feedback. The implications of the results an interpreting the findings of past experiments with liberal relevance thresholds are also discussed.
17Sihvonen, A. ; Vakkari, P.: Subject knowledge improves interactive query expansion assisted by a thesaurus.
In: Journal of documentation. 60(2004) no.6, S.673-690.
Abstract: This study explores how experts and novices in pedagogics expanded queries supported by the ERIC thesaurus, and how this was connected to the search effectiveness in an easy and a difficult search task. The expert group consisted of 15 undergraduates in pedagogy and the novice group of 15 students with no previous studies in this field. Their search logs were recorded and a pre- and post-search interview was conducted. The results show that the number and type of terms selected from the thesaurus for expansion by experts improved search effectiveness, whereas there were no connections between the use of thesaurus and improvement of effectiveness among novices. The effectiveness of expansions varied between the facets of the queries. Thus, a vital condition for benefiting from a thesaurus in query expansion to improve search results is sufficient familiarity with the search topic. The results suggest also that it is not in the first place the number of terms used in expansion, but their type and quality that are crucial for search success.
Anmerkung: Vgl. auch unter: http://www.emeraldinsight.com/10.1108/00220410410568151
Themenfeld: Konzeption und Anwendung des Prinzips Thesaurus ; Semantisches Umfeld in Indexierung u. Retrieval
18Vakkari, P. ; Jones, S. ; MacFarlane, A. ; Sormunen, E.: Query exhaustivity, relevance feedback and search success in automatic and interactive query expansion.
In: Journal of documentation. 60(2004) no.2, S.109-127.
Abstract: This study explored how the expression of search facets and relevance feedback (RF) by users was related to search success in interactive and automatic query expansion in the course of the search process. Search success was measured both in the number of relevant documents retrieved, whether identified by users or not. Research design consisted of 26 users searching for four TREC topics in Okapi IR system, half of the searchers using interactive and half automatic query expansion based on RF. The search logs were recorded, and the users filled in questionnaires for each topic concerning various features of searching. The results showed that the exhaustivity of the query was the most significant predictor of search success. Interactive expansion led to better search success than automatic expansion if all retrieved relevant items were counted, but there was no difference between the methods if only those items recognised relevant by users were observed. The analysis showed that the difference was facilitated by the liberal relevance criterion used in TREC not favouring highly relevant documents in evaluation.
Anmerkung: Vgl. auch unter: http://www.emeraldinsight.com/10.1108/00220410410522016
19Pennanen, M. ; Vakkari, P.: Students' conceptual structure, search process, and outcome while preparing a research proposal : a longitudinal case study.
In: Journal of the American Society for Information Science and technology. 54(2003) no.8, S.759-770.
Abstract: This article focuses an analysing students' information needs in terms of conceptual understanding of the topic they propose to study and its consequences for the search process and outcome. The research subjects were 22 undergraduates of psychology attending a seminar for preparing a research proposal for a small empirical study. They were asked to make searches in the PsycINFO database for their task in the beginning and end of the seminar. A pre- and postsearch interview was conducted in both sessions. The students were asked to think aloud in the sessions. This was recorded, as were the transaction logs. The results show that during the preparation of research proposals different features of the students' conceptual structure were connected to the search success. Students' ability to cover their conceptual construct by query terms was the major feature affecting search success during the whole process. In the beginning also the number of concepts and the proportion of subconcepts in the construct contributed indirectly via search tactics to retrieving partly useful references. Students' ability to extract new query terms from retrieved items improved search results.
20Vakkari, P. ; Pennanen, M. ; Serola, S.: Changes of search terms and tactics while writing a research proposal : a longitudinal case study.
In: Information processing and management. 39(2003) no.3, S.445-463.
Abstract: The study analyses how students' growing understanding of the topic and search experience were related to their choice of search tactics and terms while preparing a research proposal for a small empirical study. In addition to that, the findings of the study are used to test Vakkari's (2001) theory of task-based IR. The research subjects were 22 students of psychology attending a seminar for preparing the proposal. They made a search for their task in PsychINFO database at the beginning and end of the seminar. Data were collected in several ways. A pre- and post-search interview was conducted in both sessions. The students were asked to think aloud in the sessions. This was recorded as were the transaction logs. The results show that search experience was slightly related to the change of facets. Although the students' vocabulary of the topic grew generating an increased use of specific terms between the sessions, their use of search tactics and operators remained fairly constant. There was no correlation between the terms and tactics used and the total number of useful references found. By comparing these results with the findings of relevant earlier studies the conclusion was drawn that domain knowledge has an impact on searching assuming that users have a sufficient command of the system used. This implies that the tested theory of task-based IR is valid on condition that the searchers are experienced. It is suggested that the theory should be enriched by including search experience in its scope.