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244 Selected Studies on Software and Information Systems
User Modeling
Explicit
Social Network
Implicit
User-generated
data
formation
discovery
DB
Keywords, feedback, ...
Communication
logs
User model
Documents
the Web
Figure 8-10. Formation of a social network by explicitly collecting ratings or profiles (left). Identification
and discovery of a network by exposing self-organizing communities implicit in user-generated data
such as communication or web logs (right), according to [55].
Typically, a ratings dataset can be modeled as a bipartite graph rather than a matrix
(bipartite graph is often called affiliation network in social network theory). For example,
if we consider an affiliation network formed by people and publications they
(co)authored, we can bring people together via their relationships with publications.
– Small-World Networks – are networks naturally modeling the small-world phenomenon
(a Harvard social psychologist Stanley Milgram conceived an experiment in the late
1960’s which revealed that any two randomly picked individuals residing in the
US were connected by no more than six intermediate acquaintances and thus that
a human society is organized as a small world type network). According to [55],
small-worlds present opportunities for recommender systems. If identified, not only
do they help model users and communities implicitly by revealing social structure
(via the structure of the connections between documents which members of those
communities manually created), but also help connect people via short chains. For
example, if search engines could take advantage of the web’s small-world property,
then users with only local knowledge of the web may actually be able to find and
construct short paths between pairs of web pages.
ReferralWeb. An example of link analysis approach can be found in [32]. Authors
propose a system which supports users in searching for a piece of information by searching
the social network for an expert on the topic together with a chain of personal referrals from
the searcher to the expert. The social network is constructed automatically, querying the Web.