:ADD-RELATION

Purpose

Parameters

name

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 be created.

Examples

  (: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)

Success criteria

Failure criteria

Notes

• 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:
  • :BOOLEAN
  • :FLOAT
  • :INTEGER
  • :LIST
  • :STRING
  • :SYMBOL
• 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 allows it.

Related commands

• :ADD-CLASS
• :IS-RELATION
• :TAXONOMY

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