| Preface | 5 |
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| Contents | 7 |
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| 1 Introduction | 11 |
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| 1.1 Recommender Systems | 11 |
| 1.2 Scienti.c and Technical Information | 14 |
| 1.3 Motivation and Focus | 16 |
| 1.4 Chapter Guide | 18 |
| 2 The Market of Scienti.c and Technical Information | 19 |
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| 2.1 Information Providers in the Digital Age | 19 |
| 2.2 The 2-3-6-Value-Chain for STI Markets | 24 |
| 2.3 The Strategic Positions of the Market Players | 26 |
| 2.4 Recommender Systems in the Business Pro.le of Information Providers | 31 |
| 3 Classi.cation and Mechanism Design of Recommender Systems | 32 |
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| 3.1 Classi.cations of Recommender Systems | 32 |
| 3.2 Mechanism Design | 35 |
| 4 A Survey of Recommender Systems at Major STI Providers | 40 |
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| 4.1 Scienti.c Libraries | 40 |
| 4.2 Scienti.c Projects | 44 |
| 4.3 E-Commerce: Amazon.com | 45 |
| 4.4 Social Tagging | 48 |
| 5 Case Study: Explicit Recommender Services for Scienti.c Libraries | 52 |
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| 5.1 General Setup | 52 |
| 5.2 Rating Service | 56 |
| 5.3 Review Service | 57 |
| 5.4 Usage Statistics | 59 |
| 5.5 Discussion | 60 |
| 6 General Concepts of Behavior-Based Recommender Services | 65 |
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| 6.1 Revealed Preference Theory and Choice Sets | 65 |
| 6.2 Self-Selection | 67 |
| 6.3 Prices, Transaction Costs, Market Baskets, Lending Data, and Browser Sessions | 67 |
| 6.4 Knowledge Discovery and Data Mining | 69 |
| 6.5 Observed Users vs. Target Group of Recommendations | 69 |
| 6.6 Factors for the Di.usion of Recommendations | 70 |
| 7 Algorithms for Behavior-Based Recommender Systems | 72 |
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| 7.1 Purchase Noise Filtering by Means of the Logarithmic Series Distribution | 72 |
| 7.2 POSICI and POMICI: Recommendations from Small Samples | 83 |
| 7.3 Related Methods | 94 |
| 8 Case Study: Behavior-Based Recommender Services for Scienti.c Libraries | 97 |
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| 8.1 Service Description | 97 |
| 8.2 Implementation | 103 |
| 8.3 Evaluation | 112 |
| 8.4 BibTip: Commercial Implicit Recommendation Services for Libraries | 121 |
| 8.5 Extensions, Improvements, and Further Applications | 122 |
| 9 Visualizing and Exploring Information Spaces | 126 |
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| 9.1 A Survey of Visual Interfaces to Information Providers | 127 |
| 9.2 RecoDiver: A Graph-Based User Interface to Recommendations | 129 |
| 9.3 Evaluation | 135 |
| 9.4 Discussion and Outlook | 137 |
| 10 Discussion | 139 |
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| List of Figures | 143 |
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| List of Tables | 146 |
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| References | 147 |