Ontologies of time: Review and trends

Time, as a phenomenon, has been in the focus of scientific thought from ancient times. It continues to be an important subject of research in many disciplines due to its importance as a basic aspect for understanding and formally representing change. The goal of this analytical review is to find out if the formal representations of time developed to date suffice to the needs of the basic and applied research in Computer Science, and in particular within the Artificial Intelligence and Semantic Web communities. To analyze if the existing basic theories, models, and implemented ontologies of time cower these needs well, the set of the features of time has been extracted and appropriately structured using the paper collection of the TIME Symposia series as the document corpus. This feature set further helped to structure the comparative review and analysis of the most prominent temporal theories. As a result, the selection of the subset of the features of time (the requirements for a Synthetic Theory) has been made reflecting the TIME community sentiment. Further, the temporal logics, representation languages, and ontologies available to date, have been reviewed regarding their usability aspects and the coverage of the selected temporal features. The results reveal that the reviewed ontologies of time taken together do not satisfactorily cover some important features: (i) density; (ii) relaxed linearity; (iii) scale factors; (iv) proper and periodic subintervals; (v) temporal measures and clocks. It has been concluded that a cross-disciplinary effort is required to address the features not covered by the existing ontologies of time, and also harmonize the representations addressed differently.