Literatur zur Informationserschließung

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: 04. Juni 2021)

Suchergebnisse

• 1
  Zhitomirsky-Geffet, M. ; Bar-Ilan, J. ; Levene, M.: Categorical relevance judgment.
  In: Journal of the Association for Information Science and Technology. 69(2018) no.9, S.1084-1094.
  
  Abstract: In this study we aim to explore users' behavior when assessing search results relevance based on the hypothesis of categorical thinking. To investigate how users categories search engine results, we perform several experiments where users are asked to group a list of 20 search results into several categories, while attaching a relevance judgment to each formed category. Moreover, to determine how users change their minds over time, each experiment was repeated three times under the same conditions, with a gap of one month between rounds. The results show that on average users form 4-5 categories. Within each round the size of a category decreases with the relevance of a category. To measure the agreement between the search engine's ranking and the users' relevance judgments, we defined two novel similarity measures, the average concordance and the MinMax swap ratio. Similarity is shown to be the highest for the third round as the users' opinion stabilizes. Qualitative analysis uncovered some interesting points that users tended to categories results by type and reliability of their source, and particularly, found commercial sites less trustworthy, and attached high relevance to Wikipedia when their prior domain knowledge was limited.
  
  Inhalt: Vgl.: https://onlinelibrary.wiley.com/doi/10.1002/asi.24035.
  
  
  
• 2
  Zhitomirsky-Geffet, M. ; Erez, E.S. ; Bar-Ilan, J.: Toward multiviewpoint ontology construction by collaboration of non-experts and crowdsourcing : the case of the effect of diet on health.
  In: Journal of the Association for Information Science and Technology. 68(2017) no.3, S.681-694.
  
  Abstract: Domain experts are skilled in buliding a narrow ontology that reflects their subfield of expertise based on their work experience and personal beliefs. We call this type of ontology a single-viewpoint ontology. There can be a variety of such single viewpoint ontologies that represent a wide spectrum of subfields and expert opinions on the domain. However, to have a complete formal vocabulary for the domain they need to be linked and unified into a multiviewpoint model while having the subjective viewpoint statements marked and distinguished from the objectively true statements. In this study, we propose and implement a two-phase methodology for multiviewpoint ontology construction by nonexpert users. The proposed methodology was implemented for the domain of the effect of diet on health. A large-scale crowdsourcing experiment was conducted with about 750 ontological statements to determine whether each of these statements is objectively true, viewpoint, or erroneous. Typically, in crowdsourcing experiments the workers are asked for their personal opinions on the given subject. However, in our case their ability to objectively assess others' opinions was examined as well. Our results show substantially higher accuracy in classification for the objective assessment approach compared to the results based on personal opinions.
  
  Inhalt: Vgl.: http://onlinelibrary.wiley.com/doi/10.1002/asi.23686/full.
  
  Themenfeld: Wissensrepräsentation
  Wissenschaftsfach: Medizin
  
  
• 3
  Zhitomirsky-Geffet, M. ; Bar-Ilan, J. ; Levene, M.: Analysis of change in users' assessment of search results over time.
  In: Journal of the Association for Information Science and Technology. 68(2017) no.5, S.1137-1148.
  
  Abstract: We present the first systematic study of the influence of time on user judgements for rankings and relevance grades of web search engine results. The goal of this study is to evaluate the change in user assessment of search results and explore how users' judgements change. To this end, we conducted a large-scale user study with 86 participants who evaluated 2 different queries and 4 diverse result sets twice with an interval of 2 months. To analyze the results we investigate whether 2 types of patterns of user behavior from the theory of categorical thinking hold for the case of evaluation of search results: (a) coarseness and (b) locality. To quantify these patterns we devised 2 new measures of change in user judgements and distinguish between local (when users swap between close ranks and relevance values) and nonlocal changes. Two types of judgements were considered in this study: (a) relevance on a 4-point scale, and (b) ranking on a 10-point scale without ties. We found that users tend to change their judgements of the results over time in about 50% of cases for relevance and in 85% of cases for ranking. However, the majority of these changes were local.
  
  Inhalt: Vgl.: http://onlinelibrary.wiley.com/doi/10.1002/asi.23745/full.
  
  Themenfeld: Suchmaschinen ; Benutzerstudien
  
  
• 4
  Zhitomirsky-Geffet, M. ; Bar-Ilan, J. ; Levene, M.: Testing the stability of "wisdom of crowds" judgments of search results over time and their similarity with the search engine rankings.
  In: Aslib journal of information management. 68(2016) no.4, S.407-427.
  
  Abstract: Purpose - One of the under-explored aspects in the process of user information seeking behaviour is influence of time on relevance evaluation. It has been shown in previous studies that individual users might change their assessment of search results over time. It is also known that aggregated judgements of multiple individual users can lead to correct and reliable decisions; this phenomenon is known as the "wisdom of crowds". The purpose of this paper is to examine whether aggregated judgements will be more stable and thus more reliable over time than individual user judgements. Design/methodology/approach - In this study two simple measures are proposed to calculate the aggregated judgements of search results and compare their reliability and stability to individual user judgements. In addition, the aggregated "wisdom of crowds" judgements were used as a means to compare the differences between human assessments of search results and search engine's rankings. A large-scale user study was conducted with 87 participants who evaluated two different queries and four diverse result sets twice, with an interval of two months. Two types of judgements were considered in this study: relevance on a four-point scale, and ranking on a ten-point scale without ties. Findings - It was found that aggregated judgements are much more stable than individual user judgements, yet they are quite different from search engine rankings. Practical implications - The proposed "wisdom of crowds"-based approach provides a reliable reference point for the evaluation of search engines. This is also important for exploring the need of personalisation and adapting search engine's ranking over time to changes in users preferences. Originality/value - This is a first study that applies the notion of "wisdom of crowds" to examine an under-explored in the literature phenomenon of "change in time" in user evaluation of relevance.
  
  Inhalt: Vgl.: http://www.emeraldinsight.com/doi/abs/10.1108/AJIM-10-2015-0165.
  
  
  
• 5
  Bronstein, J. ; Gazit, T. ; Perez, O. ; Bar-Ilan, J. ; Aharony, N. ; Amichai-Hamburger, Y.: ¬An examination of the factors contributing to participation in online social platforms.
  In: Aslib journal of information management. 68(2016) no.6, S.793-818.
  
  Abstract: Purpose The purpose of this paper is to examine participation in online social platforms consisting of information exchange, social network interactions, and political deliberation. Despite the proven benefits of online participation, the majority of internet users read social media data but do not directly contribute, a phenomenon called lurking. Design/methodology/approach A survey was administered electronically to 507 participants and consisted of ten sections in a questionnaire to gather data on the relationship between online participation and the following variables: anonymity, social value orientation, motivations, and participation in offline activities, as well as the internet's political influence and personality traits. Findings Findings show that users with high levels of participation also identify themselves, report higher levels of extroversion, openness, and activity outside the internet, the motivations being an intermediary variable in the relationship between the variables value. Originality/value The study shows that participation in online social platforms is not only related to personality traits, but they are impacted by the nature of the motivations that drive them to participate in the particular social platform, as well as by the interest toward the specific topic, or the type or nature of the social group with whom they are communicating.
  
  Inhalt: Vgl.: http://www.emeraldinsight.com/doi/full/10.1108/AJIM-05-2016-0059.
  
  
  
• 6
  Bar-Ilan, J. ; Levene, M.: ¬The hw-rank : an h-index variant for ranking web pages.
  In: Scientometrics. 102(2015) no.3, S.2247-2253.
  
  Inhalt: Vgl.: doi:10.1007/s11192-014-1477-2
  
  Anmerkung: Beitrag in einem Special Issue "Combining bibliometrics and information retrieval"
  
  Themenfeld: Informetrie ; Retrievalalgorithmen
  
  
• 7
  Shema, H. ; Bar-Ilan, J. ; Thelwall, M.: How is research blogged? : A content analysis approach.
  In: Journal of the Association for Information Science and Technology. 66(2015) no.6, S.1136-1149.
  
  Abstract: Blogs that cite academic articles have emerged as a potential source of alternative impact metrics for the visibility of the blogged articles. Nevertheless, to evaluate more fully the value of blog citations, it is necessary to investigate whether research blogs focus on particular types of articles or give new perspectives on scientific discourse. Therefore, we studied the characteristics of peer-reviewed references in blogs and the typical content of blog posts to gain insight into bloggers' motivations. The sample consisted of 391 blog posts from 2010 to 2012 in Researchblogging.org's health category. The bloggers mostly cited recent research articles or reviews from top multidisciplinary and general medical journals. Using content analysis methods, we created a general classification scheme for blog post content with 10 major topic categories, each with several subcategories. The results suggest that health research bloggers rarely self-cite and that the vast majority of their blog posts (90%) include a general discussion of the issue covered in the article, with more than one quarter providing health-related advice based on the article(s) covered. These factors suggest a genuine attempt to engage with a wider, nonacademic audience. Nevertheless, almost 30% of the posts included some criticism of the issues being discussed.
  
  Inhalt: Vgl.: http://onlinelibrary.wiley.com/doi/10.1002/asi.23239/abstract.
  
  Themenfeld: Informetrie
  
  
• 8
  Shema, H. ; Bar-Ilan, J. ; Thelwall, M.: Do blog citations correlate with a higher number of future citations? : Research blogs as a potential source for alternative metrics.
  In: Journal of the Association for Information Science and Technology. 65(2014) no.5, S.1018-1027.
  
  Abstract: Journal-based citations are an important source of data for impact indices. However, the impact of journal articles extends beyond formal scholarly discourse. Measuring online scholarly impact calls for new indices, complementary to the older ones. This article examines a possible alternative metric source, blog posts aggregated at ResearchBlogging.org, which discuss peer-reviewed articles and provide full bibliographic references. Articles reviewed in these blogs therefore receive "blog citations." We hypothesized that articles receiving blog citations close to their publication time receive more journal citations later than the articles in the same journal published in the same year that did not receive such blog citations. Statistically significant evidence for articles published in 2009 and 2010 support this hypothesis for seven of 12 journals (58%) in 2009 and 13 of 19 journals (68%) in 2010. We suggest, based on these results, that blog citations can be used as an alternative metric source.
  
  Themenfeld: Informetrie
  
  
• 9
  Zhitomirsky-Geffet, M. ; Bar-Ilan, J.: Towards maximal unification of semantically diverse ontologies for controversial domains.
  In: Aslib journal of information management. 66(2014) no.5, S.494-518.
  (Special issue: Semantic search)
  
  Abstract: Purpose - Ontologies are prone to wide semantic variability due to subjective points of view of their composers. The purpose of this paper is to propose a new approach for maximal unification of diverse ontologies for controversial domains by their relations. Design/methodology/approach - Effective matching or unification of multiple ontologies for a specific domain is crucial for the success of many semantic web applications, such as semantic information retrieval and organization, document tagging, summarization and search. To this end, numerous automatic and semi-automatic techniques were proposed in the past decade that attempt to identify similar entities, mostly classes, in diverse ontologies for similar domains. Apparently, matching individual entities cannot result in full integration of ontologies' semantics without matching their inter-relations with all other-related classes (and instances). However, semantic matching of ontological relations still constitutes a major research challenge. Therefore, in this paper the authors propose a new paradigm for assessment of maximal possible matching and unification of ontological relations. To this end, several unification rules for ontological relations were devised based on ontological reference rules, and lexical and textual entailment. These rules were semi-automatically implemented to extend a given ontology with semantically matching relations from another ontology for a similar domain. Then, the ontologies were unified through these similar pairs of relations. The authors observe that these rules can be also facilitated to reveal the contradictory relations in different ontologies. Findings - To assess the feasibility of the approach two experiments were conducted with different sets of multiple personal ontologies on controversial domains constructed by trained subjects. The results for about 50 distinct ontology pairs demonstrate a good potential of the methodology for increasing inter-ontology agreement. Furthermore, the authors show that the presented methodology can lead to a complete unification of multiple semantically heterogeneous ontologies. Research limitations/implications - This is a conceptual study that presents a new approach for semantic unification of ontologies by a devised set of rules along with the initial experimental evidence of its feasibility and effectiveness. However, this methodology has to be fully automatically implemented and tested on a larger dataset in future research. Practical implications - This result has implication for semantic search, since a richer ontology, comprised of multiple aspects and viewpoints of the domain of knowledge, enhances discoverability and improves search results. Originality/value - To the best of the knowledge, this is the first study to examine and assess the maximal level of semantic relation-based ontology unification.
  
  Inhalt: Vgl.: http://dx.doi.org/10.1108/AJIM-12-2013-0148.
  
  Themenfeld: Wissensrepräsentation ; Semantic Web
  
  
• 10
  Bergman, O. ; Gradovitch, N. ; Bar-Ilan, J. ; Beyth-Marom, R.: Folder versus tag preference in personal information management.
  In: Journal of the American Society for Information Science and Technology. 64(2013) no.10, S.1995-2012.
  
  Abstract: Users' preferences for folders versus tags was studied in 2 working environments where both options were available to them. In the Gmail study, we informed 75 participants about both folder-labeling and tag-labeling, observed their storage behavior after 1 month, and asked them to estimate the proportions of different retrieval options in their behavior. In the Windows 7 study, we informed 23 participants about tags and asked them to tag all their files for 2 weeks, followed by a period of 5 weeks of free choice between the 2 methods. Their storage and retrieval habits were tested prior to the learning session and, after 7 weeks, using special classification recording software and a retrieval-habits questionnaire. A controlled retrieval task and an in-depth interview were conducted. Results of both studies show a strong preference for folders over tags for both storage and retrieval. In the minority of cases where tags were used for storage, participants typically used a single tag per information item. Moreover, when multiple classification was used for storage, it was only marginally used for retrieval. The controlled retrieval task showed lower success rates and slower retrieval speeds for tag use. Possible reasons for participants' preferences are discussed.
  
  Themenfeld: Katalogfragen allgemein ; Benutzerstudien
  
  
• 11
  Bar-Ilan, J. ; Azoulay, R.: Map of nonprofit organization websites in Israel.
  In: Journal of the American Society for Information Science and Technology. 63(2012) no.6, S.1142-1167.
  
  Abstract: In this study, we consider the structure and linking strategy of Hebrew websites of several nonprofit organizations. Because nonprofit organizations differ from commercial, educational, or governmental sectors, it is important to understand the ways they utilize the web. To the best of our knowledge, the linking structure of nonprofit organizations has not been previously studied. We surveyed websites of 54 nonprofit organizations in Israel; most of these sites have at least 100 volunteers. We compared their orientation and contents and we built their linking map. We divided the organizations into four main groups: economic aid and citizen rights organizations, health aid organizations, organizations supporting families and individuals with special needs, and organizations for women and children. We found that the number of links inside the special needs group is much higher than in the other groups. We tried to explain this behavior by considering the data obtained from the site-linking graph. The value of our results is in defining and testing a method to investigate a group of nonprofit organizations, using a case study of Israeli organizations.
  
  Land/Ort: Israel
  
  
• 12
  Barsky, E. ; Bar-Ilan, J.: ¬The impact of task phrasing on the choice of search keywords and on the search process and success.
  In: Journal of the American Society for Information Science and Technology. 63(2012) no.10, S.1987-2005.
  
  Abstract: This experiment studied the impact of various task phrasings on the search process. Eighty-eight searchers performed four web search tasks prescribed by the researchers. Each task was linked to an existing target web page, containing a piece of text that served as the basis for the task. A matching phrasing was a task whose wording matched the text of the target page. A nonmatching phrasing was synonymous with the matching phrasing, but had no match with the target page. Searchers received tasks for both types in English and in Hebrew. The search process was logged. The findings confirm that task phrasing shapes the search process and outcome, and also user satisfaction. Each search stage-retrieval of the target page, visiting the target page, and finding the target answer-was associated with different phenomena; for example, target page retrieval was negatively affected by persistence in search patterns (e.g., use of phrases), user-originated keywords, shorter queries, and omitting key keywords from the queries. Searchers were easily driven away from the top-ranked target pages by lower-ranked pages with title tags matching the queries. Some searchers created consistently longer queries than other searchers, regardless of the task length. Several consistent behavior patterns that characterized the Hebrew language were uncovered, including the use of keyword modifications (replacing infinitive forms with nouns), omitting prefixes and articles, and preferences for the common language. The success self-assessment also depended on whether the wording of the answer matched the task phrasing.
  
  Themenfeld: Suchtaktik
  
  
• 13
  Bar-Ilan, J. ; Zhitomirsky-Geffet, M. ; Miller, Y. ; Shoham, S.: ¬The effects of background information and social interaction on image tagging.
  In: Journal of the American Society for Information Science and Technology. 61(2010) no.5, S.940-951.
  
  Abstract: In this article, we describe the results of an experiment designed to understand the effects of background information and social interaction on image tagging. The participants in the experiment were asked to tag 12 preselected images of Jewish cultural heritage. The users were partitioned into three groups: the first group saw only the images with no additional information whatsoever, the second group saw the images plus a short, descriptive title, and the third group saw the images, the titles, and the URL of the page in which the image appeared. In the first stage of the experiment, each user tagged the images without seeing the tags provided by the other users. In the second stage, the users saw the tags assigned by others and were encouraged to interact. Results show that after the social interaction phase, the tag sets converged and the popular tags became even more popular. Although in all cases the total number of assigned tags increased after the social interaction phase, the number of distinct tags decreased in most cases. When viewing the image only, in some cases the users were not able to correctly identify what they saw in some of the pictures, but they overcame the initial difficulties after interaction. We conclude from this experiment that social interaction may lead to convergence in tagging and that the wisdom of the crowds helps overcome the difficulties due to the lack of information.
  
  Themenfeld: Social tagging ; Internet
  Behandelte Form: Bilder
  
  
• 14
  Bar-Ilan, J. ; Keenoy, K. ; Levene, M. ; Yaari, E.: Presentation bias is significant in determining user preference for search results : a user study.
  In: Journal of the American Society for Information Science and Technology. 60(2009) no.1, S.135-149.
  
  Abstract: We describe the results of an experiment designed to study user preferences for different orderings of search results from three major search engines. In the experiment, 65 users were asked to choose the best ordering from two different orderings of the same set of search results: Each pair consisted of the search engine's original top-10 ordering and a synthetic ordering created from the same top-10 results retrieved by the search engine. This process was repeated for 12 queries and nine different synthetic orderings. The results show that there is a slight overall preference for the search engines' original orderings, but the preference is rarely significant. Users' choice of the best result from each of the different orderings indicates that placement on the page (i.e., whether the result appears near the top) is the most important factor used in determining the quality of the result, not the actual content displayed in the top-10 snippets. In addition to the placement bias, we detected a small bias due to the reputation of the sites appearing in the search results.
  
  
  
• 15
  Bar-Ilan, J. ; Peritz, B.C.: ¬A method for measuring the evolution of a topic on the Web : the case of "informetrics".
  In: Journal of the American Society for Information Science and Technology. 60(2009) no.9, S.1730-1740.
  
  Abstract: The universe of information has been enriched by the creation of the World Wide Web, which has become an indispensible source for research. Since this source is growing at an enormous speed, an in-depth look of its performance to create a method for its evaluation has become necessary; however, growth is not the only process that influences the evolution of the Web. During their lifetime, Web pages may change their content and links to/from other Web pages, be duplicated or moved to a different URL, be removed from the Web either temporarily or permanently, and be temporarily inaccessible due to server and/or communication failures. To obtain a better understanding of these processes, we developed a method for tracking topics on the Web for long periods of time, without the need to employ a crawler and relying only on publicly available resources. The multiple data-collection methods used allow us to discover new pages related to the topic, to identify changes to existing pages, and to detect previously existing pages that have been removed or whose content is not relevant anymore to the specified topic. The method is demonstrated through monitoring Web pages that contain the term informetrics for a period of 8 years. The data-collection method also allowed us to analyze the dynamic changes in search engine coverage, illustrated here on Google - the search engine used for the longest period of time for data collection in this project.
  
  Themenfeld: Informetrie
  Objekt: WWW
  
  
• 16
  Bar-Ilan, J.: Informetrics.
  In: Encyclopedia of library and information sciences. 3rd ed. Ed.: M.J. Bates. London : Taylor & Francis, 2009. S.xx-xx.
  
  Abstract: Informetrics is a subfield of information science and it encompasses bibliometrics, scientometrics, cybermetrics, and webometrics. This encyclopedia entry provides an overview of informetrics and its subfields. In general, informetrics deals with quantitative aspects of information: its production, dissemination, evaluation, and use. Bibliometrics and scientometrics study scientific literature: papers, journals, patents, and citations; while in webometric studies the sources studied are Web pages and Web sites, and citations are replaced by hypertext links. The entry introduces major topics in informetrics: citation analysis and citation related studies, the journal impact factor, the recently defined h-index, citation databases, co-citation analysis, open access publications and its implications, informetric laws, techniques for mapping and visualization of informetric phenomena, the emerging subfields of webometrics, cybermetrics and link analysis, and research evaluation.
  
  Anmerkung: Vgl.: http://www.tandfonline.com/doi/book/10.1081/E-ELIS3.
  
  Themenfeld: Informetrie
  
  
• 17
  Bar-Ilan, J. ; Belous, Y.: Children as architects of Web directories : an exploratory study.
  In: Journal of the American Society for Information Science and Technology. 58(2007) no.6, S.895-907.
  
  Abstract: Children are increasingly using the Web. Cognitive theory tells us that directory structures are especially suited for information retrieval by children; however, empirical results show that they prefer keyword searching. One of the reasons for these findings could be that the directory structures and terminology are created by grown-ups. Using a card-sorting method and an enveloping system, we simulated the structure of a directory. Our goal was to try to understand what browsable, hierarchical subject categories children create when suggested terms are supplied and they are free to add or delete terms. Twelve groups of four children each (fourth and fifth graders) participated in our exploratory study. The initial terminology presented to the children was based on names of categories used in popular directories, in the sections on Arts, Television, Music, Cinema, and Celebrities. The children were allowed to introduce additional cards and change the terms appearing on the 61 cards. Findings show that the different groups reached reasonable consensus; the majority of the category names used by existing directories were acceptable by them and only a small minority of the terms caused confusion. Our recommendation is to include children in the design process of directories, not only in designing the interface but also in designing the content structure as well.
  
  Themenfeld: Folksonomies ; Klassifikationssysteme im Online-Retrieval ; Suchmaschinen ; Benutzerstudien
  
  
• 18
  Bar-Ilan, J. ; Keenoy, K. ; Yaari, E. ; Levene, M.: User rankings of search engine results.
  In: Journal of the American Society for Information Science and Technology. 58(2007) no.9, S.1254-1266.
  
  Abstract: In this study, we investigate the similarities and differences between rankings of search results by users and search engines. Sixty-seven students took part in a 3-week-long experiment, during which they were asked to identify and rank the top 10 documents from the set of URLs that were retrieved by three major search engines (Google, MSN Search, and Yahoo!) for 12 selected queries. The URLs and accompanying snippets were displayed in random order, without disclosing which search engine(s) retrieved any specific URL for the query. We computed the similarity of the rankings of the users and search engines using four nonparametric correlation measures in [0,1] that complement each other. The findings show that the similarities between the users' choices and the rankings of the search engines are low. We examined the effects of the presentation order of the results, and of the thinking styles of the participants. Presentation order influences the rankings, but overall the results indicate that there is no "average user," and even if the users have the same basic knowledge of a topic, they evaluate information in their own context, which is influenced by cognitive, affective, and physical factors. This is the first large-scale experiment in which users were asked to rank the results of identical queries. The analysis of the experimental results demonstrates the potential for personalized search.
  
  Themenfeld: Suchmaschinen ; Benutzerstudien
  Objekt: Google ; MSN Search ; Yahoo
  
  
• 19
  Bar-Ilan, J.: Web links and search engine ranking : the case of Google and the query "Jew".
  In: Journal of the American Society for Information Science and Technology. 57(2006) no.12, S.1581-1589.
  
  Abstract: The World Wide Web has become one of our more important information sources, and commercial search engines are the major tools for locating information; however, it is not enough for a Web page to be indexed by the search engines-it also must rank high on relevant queries. One of the parameters involved in ranking is the number and quality of links pointing to the page, based on the assumption that links convey appreciation for a page. This article presents the results of a content analysis of the links to two top pages retrieved by Google for the query "jew" as of July 2004: the "jew" entry on the free online encyclopedia Wikipedia, and the home page of "Jew Watch," a highly anti-Semitic site. The top results for the query "jew" gained public attention in April 2004, when it was noticed that the "Jew Watch" homepage ranked number 1. From this point on, both sides engaged in "Googlebombing" (i.e., increasing the number of links pointing to these pages). The results of the study show that most of the links to these pages come from blogs and discussion links, and the number of links pointing to these pages in appreciation of their content is extremely small. These findings have implications for ranking algorithms based on link counts, and emphasize the huge difference between Web links and citations in the scientific community.
  
  Themenfeld: Suchmaschinen
  Objekt: Google ; Wikipedia
  
  
• 20
  Bar-Ilan, J. ; Levene, M. ; Mat-Hassan, M.: Methods for evaluating dynamic changes in search engine rankings : a case study.
  In: Journal of documentation. 62(2006) no.6, S.708-729.
  
  Abstract: Purpose - The objective of this paper is to characterize the changes in the rankings of the top ten results of major search engines over time and to compare the rankings between these engines. Design/methodology/approach - The papers compare rankings of the top-ten results of the search engines Google and AlltheWeb on ten identical queries over a period of three weeks. Only the top-ten results were considered, since users do not normally inspect more than the first results page returned by a search engine. The experiment was repeated twice, in October 2003 and in January 2004, in order to assess changes to the top-ten results of some of the queries during the three months interval. In order to assess the changes in the rankings, three measures were computed for each data collection point and each search engine. Findings - The findings in this paper show that the rankings of AlltheWeb were highly stable over each period, while the rankings of Google underwent constant yet minor changes, with occasional major ones. Changes over time can be explained by the dynamic nature of the web or by fluctuations in the search engines' indexes. The top-ten results of the two search engines had surprisingly low overlap. With such small overlap, the task of comparing the rankings of the two engines becomes extremely challenging. Originality/value - The paper shows that because of the abundance of information on the web, ranking search results is of extreme importance. The paper compares several measures for computing the similarity between rankings of search tools, and shows that none of the measures is fully satisfactory as a standalone measure. It also demonstrates the apparent differences in the ranking algorithms of two widely used search engines.
  
  Themenfeld: Suchmaschinen ; Retrievalalgorithmen