Creates a new relation (called a slot or property in some KBMS).
The user can optionally specify properties of the relation such as
maximum cardinality and a default value.
- The name of the new relation.
- (domain-class range)
- The domain and range (also called from
and to) of the relation.
- :MIN-CARDINALITY (optional, default 0)
- Specifies the minimum cardinality of the relation (how
many values it can hold). The default is zero, which
means that the relation is not required for a frame.
- :MAX-CARDINALITY (optional, default 1)
- Specifies the maximum cardinality of the relation (how
many values it can hold). The default is one. Use :ANY to
specify unlimited maximum cardinality.
- :DEFAULT (optional, default is none)
- Specifies the default value of the relation which is
stored in new instances of the relation if a value is
not given when the relation instance is created.
- :INVERSE (optional, default is none)
- Specifies the name of the inverse of this relation.
In most KBMS, when a relation is created from frame A to
frame B, its inverse is also automatically created from
frame B to frame A. The inverse relation must already
(:ADD-RELATION Color (Physical_Objects Colors))
(:ADD-RELATION Length (Physical_Objects :INTEGER))
(:ADD-RELATION Pet (Humans Animals) :MAX-CARDINALITY 10 :DEFAULT Rover :INVERSE OwnedBy)
(:ADD-RELATION Friend (Humans Humans) :MAX-CARDINALITY :ANY)
Succeeds if the relation is successfully created.
Fails if the relation can not be created.
- The domain and range classes of the new class must already exist.
- The domain must always be a class.
- The range may be a class or a data type. The allowed data types are:
- MAX-CARDINALITY, if specified, must be greater than MIN-CARDINALITY.
- The INVERSE relation must already exist.
- The DEFAULT value must be a legal value for the relation.
- In some KBMS, such as Protege, the same relation can be created multiple times
with different domains and ranges. This is legal in Algernon if the KBMS backend
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