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## Slot constraints

A slot-constraint consists of a slot name followed by one or more constraints that apply to the slot, written . Each constraint can be either:

• A value constraint with either a list of one or more class-expressions or a list of one or more concrete type expressions, written .
• A value-type constraint with either a list of one or more class-expressions or a list of one or more concrete type expressions, written .
• A has-filler constraint with either a list of one or more individual names or a list of one or more data values, written .
• A max-cardinality constraint with a non-negative integer followed (optionally) by either a class expression or a concrete-type-expression, written ( if the expression is omitted).
• A min-cardinality constraint with a non-negative integer followed (optionally) by either a class expression or a concrete type expression, written ( if the expression is omitted).
• A cardinality constraint with a non-negative integer followed (optionally) by either a class expression or a concrete type expression, written ( if the class expression is omitted).

In order to maintain the decidability of the language, cardinality constraints can only be applied to simple slots. A simple slot is one that is neither transitive nor has any transitive subslots. However, as the transitivity of a slot can be inferred (e.g., from the fact that the inverse of the slot is a transitive slot), simple slot is defined in terms of the translation into : a slot in an ontology is a simple slot iff is a simple role in the terminology .

Next: Axioms Up: OIL-Lite Previous: Concrete type expressions
Ian Horrocks 2000-09-10