flex Expert System Toolkit - LPIS

8. Run-Time Interpretation of KSL 111
Dereferencing of KSL Objects
The following table shows the method by which Prolog terms (and thus KSL objects)
are dereferenced.
Term
N
T
Dereferenced Value
Get the current value for global variable N and
dereference it
T, whenever T is an atomic term
[E 1
, … ,E k
] [T 1
, … ,T k
] where each E i
dereferences to T i
or([E 1
, … ,E k
])
Choose some E i
and dereference it to T i
@(A,F) First of all, dereference A and F to A1 and F1,
respectively; then get the current value, the default
value or an inherited value for attribute A1 of frame
F1, and dereference it; during the subsidiary
dereferencing F1 becomes the original frame
its(A)
X : C
O(E l
,E r
)
O(E)
If there is an original frame F then the dereferencing
proceeds as if it were @(A,F), otherwise the structure
its(A) is returned
Execute the condition C and dereference the resulting
instance of X
Dereference the operands down to T l
and T r
; if they
are both numbers then apply the operator, otherwise
return the structure O(T l
,T r
)
Dereference the operand down to T; if it is a number
then apply the operator, otherwise return the structure
O(T)
F(E 1
,…,E k
) Dereference each E i
to some T i
; if it is a defined
function then replace with the right-hand-side of the
definition and continue dereferencing, otherwise return
the structure F(T 1
,…,T k
)
$(E)
E
flex toolkit