The representation of temporal information has been in the center of intensive research activities over the years in the areas of knowledge representation, databases and more recently, the Semantic Web. The proposed approach extends the existing fram

We propose CHRONOS, a system for reasoning over temporal information in OWL ontologies. Representing both qualitative temporal (i.e., information whose temporal extents are unknown such as “before”, “after” for temporal relations) in addition to quantitative information (i.e., where temporal information is defined precisely e.g., using dates) is a distinctive feature of the proposed approach. Qualitative representations are very common in natural language expressions such as in free text or speech and can be proven to be valuable in the Semantic Web. CHRONOS reasoner applies over temporal relations in order to infer implied relations and to detect inconsistencies while retaining soundness, completeness and tractability over the supported relations set. The experimental results demonstrated that CHRONOS runs up to several times faster compared to its SWRL counterpart and scales-up well for large relation sets.