(define-instance <instance-name> (<class-name>+)
[<docstring>]
[:= <term-expression-without-arg-vars>]
[:axiom-def <sent-without-arg-vars>]
[:slots (<slot-spec>*)]
[:theory <theory-name>]
[:implementation <target-system-name>]
[:issues <issue-tree>])
Macro for defining Ontolingua instances. No arguments are evaluated. See also CREATE-INSTANCE, which is the functional form.
<instance-name> should be a symbol which names the instance being defined. Ontolingua will convert this symbol into a format which is appropriate for the selected target representation system during translation (e.g., if one were translating into CycL, the symbol would be converted into a string which would obey the CycL conventions for case and word delimiters.)
<docstring> should be a string which describes the instance being defined. It is used in hypertext reports.
The remaining keyword arguments may occur in any order, and are described below:
:= - The value of this keyword argument should be a KIF term expression which denotes the instance being defined. For example:
(define-instance PI (real-number)
"PI is the ratio of the perimeter of a circle to its diameter."
:= 3.145)
:AXIOM-DEF - The value of this keyword argument should be a KIF sentence which mentions the instance being defined; it will be asserted when the instance is defined. Terminologically, this sentence will be considered part of the definition of the instance. For example:
(define-instance FRED (GUYS-WITH-GENERIC-NAMES)
"The canonical random person name."
:axiom-def (usual-temperament fred nice))
means that FRED is a member of the class GUYS-WITH-GENERIC-NAMES, and that FRED is usually nice. The axiom that fred is usually nice is considered part of the definition of FRED.- The value should be a KIF sentence with no free variables. In particular, the sentence does not implicitly constrain the variables in the argument list (that is what :def and :iff-def are for). The :AXIOM-DEF sentence is considered to be definitional. That is, it is part of the definition as are :DEF and :IFF-DEF sentences. Non-definition axioms should be specified with the :AXIOM-CONSTRAINTS keyword.
A list of sentences may be supplied instead of a single sentence; Ontolingua will automatically construct a conjunction of all the supplied :AXIOM-DEF sentences in this case.
:IMPLEMENTATION - The value of this keyword argument should be a symbol (usually a keyword) which names the target representation system in which the definition should be defined. This is independent of the theory in which the defined is defined. If the :IMPLEMENTATION argument is not supplied, the current implementation is assumed (see IN-IMPLEMENTATION.)
:ISSUES - The value of this argument should be a Lisp "tree" of strings. The tree can be either a string, or a list of strings, or a list of (<label> <any-lisp-object>) pairs, where <label> is a string or symbol that names the type of the comment. For examples,
:issues ("This is a footnote about FOO."
(:example (= (foo ?x) (inverse (bar ?x))))
("Why not do it this way?
:SLOTS The value of the :SLOTS keyword is a list of slot specifications. These are the same as :OWN-SLOTS used in DEFINE-CLASS.
:THEORY - The value of this keyword argument should be a symbol which names the theory in which the definition should be defined. If the :THEORY argument is not supplied, the current theory is assumed (see IN-THEORY.)
In principle one could define Ontolingua classes, relations, and functions by making them instances of CLASS, RELATION, and FUNCTION, but this is not guaranteed to do the right thing in supported implementations. For these cases, use DEFINE-CLASS, DEFINE-RELATION, and DEFINE-FUNCTION.