A model abstracts certain aspects from reality. It identifies objects, relationships, properties and attributes of the objects, relationships between objects and properties of objects, and so on. It is formally described by an order-sorted theory that imports the ontologies it uses to represent its knowledge. The knowledge representation formalism and contents of a model are respectively described by the axiom schemas (which make the syntactical structure of its axioms explicit) and axioms parts of its formal description.
sorts sort tree
constants (constantsymbol +: sortsymbol) *
functions (functionsymbol +: sortsymb sortsymbol) *
predicates (predicatesymbol +: sortsymbol *) *
variables (variablesymbol +: sortsymbol) *
axiom schemas (formulaschema +: metavariable) *
axioms (formula) *
The following examples show the formal descriptions of some models which use the ontology defined in the previous example.