flex Expert System Toolkit - LPIS

7. Knowledge Specification Language 64
KSL Objects
Variants
flex toolkit
This section describes the actual objects of KSL (i.e. constructs which
correspond to entities in your particular domain). They range from variants
which can change in value through time (by assignment) to set abstractions
which portray a collection of objects.
A variant can change in value over time (i.e. like a variable). There are
essentially two forms of variant: a straightforward global variable, or a slot.
Both of these have values associated with them.
A global variable is any name whatsoever, optionally be prefixed by the
determiner the.
Examples
staff
the staff
'today''s temperature'
A simple slot is specified by the name of an attribute and the name of the
frame (or frame instance) to which the attribute belongs, using the KSL
keyword of or the operator `s. (Note the use of the backwards quote
character `.) The attribute or frame may be optionally prefixed by the
determiner the. The general formats of slots are as follows.
frame`s attribute
attribute of frame
the attribute of the frame
Examples
Variant Schema
size of the collar
the collar`s size
the colour of money
money`s colour
The variant schema is a generalisation of slots by which the name of the
frame is only indirectly referred to. That is, the variant is a specific attribute
of some under-specified frame, rather than any particular frame.
The first kind of variant schema does not mention any particular frame at
all. These are don't care constructs, in which the name of the frame is
irrelevant, only that one exists. The general format is as follows.
attribute of anything
attribute of something