Social book search: Comparing topical relevance judgements and book suggestions for evaluation

The Web and social media give us access to a wealth of information, not only different in quantity but also in character - -traditional descriptions from professionals are now supplemented with user generated content. This challenges modern search systems based on the classical model of topical relevance and ad hoc search: How does their effectiveness transfer to the changing nature of information and to the changing types of information needs and search tasks? We use the INEX 2011 Books and Social Search Track's collection of book descriptions from Amazon and social cataloguing site LibraryThing. We compare classical IR with social book search in the context of the LibraryThing discussion forums where members ask for book suggestions. Specifically, we compare book suggestions on the forum with Mechanical Turk judgements on topical relevance and recommendation, both the judgements directly and their resulting evaluation of retrieval systems. First, the book suggestions on the forum are a complete enough set of relevance judgements for system evaluation. Second, topical relevance judgements result in a different system ranking from evaluation based on the forum suggestions. Although it is an important aspect for social book search, topical relevance is not sufficient for evaluation. Third, professional metadata alone is often not enough to determine the topical relevance of a book. User reviews provide a better signal for topical relevance. Fourth, user-generated content is more effective for social book search than professional metadata. Based on our findings, we propose an experimental evaluation that better reflects the complexities of social book search.