In order to provide compatibility with Edinburgh Prolog, the KnowledgeWorks backward chaining system treats Prolog structured terms differently from lists. Structured terms whose functors are not `.' are stored as simple vectors with the functor as element
0
(for example, the term:
foo(bar)
is equivalent to
#(foo bar)
).
KnowledgeWorks and Prolog User Guide (Windows version) - 6 Dec 2011