Exploiting Social Relations for Query Expansionand Result Ranking
Matthias Bender, Tom Crecelius, Mouna Kacimi, Sebastian Michel, Thomas
Neumann, Josiane Xavier Parreira, Ralf Schenkel, Gerhard Weikumza
This paper was presented by Mouna Kacimi.
This paper is about Query expansion in social networks and addresses the question of defining the valuable content to users in rich, online communities. Mouna suggests that one way to improve the search experience is by utilizing the social network information. The paper defines a social graph and provides scoring mechanism for finding and ranking relevant content for each node. In social networks, users can be both producers and consumers of information.Typically, the user has documents (photos, posts, etc) and tags. There are relations between nodes of the same type, for example
- friendship between nodes
- similarity between text
- similarity between tags
- linkage between the documents
Further there can be relations between nodes of different types:
- Between tags and document
- users and tags -- how imp is this tag for a user;
- user can also have a relation with documents in terms of ratings
This paper presents a generic framework for ranking relevant information for a given user; by utilizing the various elements of the social information. The scoring model can be thought of as a means of querying what your friends think about the relevance of the given information. It combines the following pieces of information:
- what your friends think of this document
- how strong is your friendship with your friend
- user rank for the friend who described the document
- document rank of the document.
Note that the authors have considered an independence assumption in computing the scores. I am not certain if this is a good assumption, but it would be one simple way of combining the scores.
In order to do query expansion, i "ask" my friends about Paris, friend's documents about paris are retrieved and other similar tags are obtained. These are used to compute the query expansion. Friendship strength is computed using the "social distance" while the tag similarity is computed based on co-occurence of the tags.
I was surprised by their finding that social search works better in flickr but not very well in del.icio.us. I think that this is because the social networks of del.icio.us are very sparse. The meaning of friendship is also different here (aka friends and fans).
However, Mouna also pointed out that an improved version of their technique has been accepted at SIGIR 2008 and has a more detailed analysis. I look forward to checking out their extended paper. What I really liked about this paper was that it was a generic framework for combining social information (network, tags, documents, etc) and can be extended in ways that would be suitable for a particular type of network or task.