204,557 research outputs found
Query-Answer Causality in Databases: Abductive Diagnosis and View-Updates
Causality has been recently introduced in databases, to model, characterize
and possibly compute causes for query results (answers). Connections between
query causality and consistency-based diagnosis and database repairs (wrt.
integrity constrain violations) have been established in the literature. In
this work we establish connections between query causality and abductive
diagnosis and the view-update problem. The unveiled relationships allow us to
obtain new complexity results for query causality -the main focus of our work-
and also for the two other areas.Comment: To appear in Proc. UAI Causal Inference Workshop, 2015. One example
was fixe
Social Structure and Opinion Formation
We present a dynamical theory of opinion formation that takes explicitly into
account the structure of the social network in which in- dividuals are
embedded. The theory predicts the evolution of a set of opinions through the
social network and establishes the existence of a martingale property, i.e.
that the expected weighted fraction of the population that holds a given
opinion is constant in time. Most importantly, this weighted fraction is not
either zero or one, but corresponds to a non-trivial distribution of opinions
in the long time limit. This co-existence of opinions within a social network
is in agreement with the often observed locality effect, in which an opinion or
a fad is localized to given groups without infecting the whole society. We
verified these predictions, as well as those concerning the fragility of
opinions and the importance of highly connected individuals in opinion
formation, by performing computer experiments on a number of social networks
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