Relation Extraction refers to the task of populating a database with tuples
of the form $r(e_1, e_2)$, where $r$ is a relation and $e_1$, $e_2$ are
entities. Distant supervision is one such technique which tries to
automatically generate training examples based on an existing KB such as
Freebase. This paper is a survey of some of the techniques in distant
supervision which primarily rely on Probabilistic Graphical Models (PGMs)