The ontology is a directed graph where nodes are concepts. Links between nodes are represented as slots and fillers. Slot names themselves are the class of concepts known as Properties except for the names of some ``bookkeeping'' slots. Links are in fact multi-dimensional since each link can have several facets. Each facet can take one or more fillers. No importance is attached to the order of multiple fillers in a slot. A complete BNF description of the ontology is provided in Appendix A. A corresponding set of axioms defining the structure of the ontology is shown in Appendix B at the end of this report.
Formally the ontology is a graph with only two kinds of patterns in
its subgraphs. The structure of these patterns will be elaborated
further below. All concepts in the ontology are classified into one
of OBJECTs, EVENTs, or Properties. OBJECTs and EVENTs are stand alone
concepts; they are instantiated in the TMR. Properties, on the other
hand, are not normally individually instantiated;
they become slots in OBJECTs and EVENTs.
As such, Properties do not have other Properties. They are specified
only in terms of their Domains and Ranges.
Properties are of two types: Relations and Attributes. Corresponding to these two are the two subgraph patterns that constitute the ontology (shown in Section 0.2 below). Relations are different from Attributes in that Relations map an OBJECTor EVENT to another OBJECT or EVENT while Attributes map an OBJECT or an EVENT to a scalar or a literal symbol. In other words, a filler of an Attribute slot is a number, a literal symbol, a mathematical expression involving numbers such as a range specification, or, in unfortunate cases, an undefined symbol not in the known set of literals.
Kavi Mahesh