  We present, FT-SWRL, a fuzzy temporal extension to the Semantic Web Rule
Language (SWRL), which combines fuzzy theories based on the valid-time temporal
model to provide a standard approach for modeling imprecise temporal domain
knowledge in OWL ontologies. The proposal introduces a fuzzy temporal model for
the semantic web, which is syntactically defined as a fuzzy temporal SWRL
ontology (SWRL-FTO) with a new set of fuzzy temporal SWRL built-ins for
defining their semantics. The SWRL-FTO hierarchically defines the necessary
linguistic terminologies and variables for the fuzzy temporal model. An example
model demonstrating the usefulness of the fuzzy temporal SWRL built-ins to
model imprecise temporal information is also represented. Fuzzification process
of interval-based temporal logic is further discussed as a reasoning paradigm
for our FT-SWRL rules, with the aim of achieving a complete OWL-based fuzzy
temporal reasoning. Literature review on fuzzy temporal representation
approaches, both within and without the use of ontologies, led to the
conclusion that the FT-SWRL model can authoritatively serve as a formal
specification for handling imprecise temporal expressions on the semantic web.
