The well designed data mining systems should present results
and discovered patterns in a formal and structured format,
so that data mining results are capable to be interpreted as
domain knowledge and to further enrich and improve current
knowledge bases. Ontology is one of the way to represent the
data mining results in a formal and structured way. As a formal
definition of concepts and relationships, ontology can encode
rich semantics for different domains. The data mining results
from different domains and tasks conform naturally with the
representation of ontology, for example, information extraction
and association rule mining. Specifically, in ontology-based
information extraction (OBIE) [55], [77], the extracted information
are a set of annotated terms from the document with
the relations defined in the ontology. It is therefore straight
forward to represent the extracted information with ontology