It is possible to type logic definitions directly into the interpreter. The resulting Lisp code will be compiled in memory and you may use the definition immediately, for example.:
|==> (defrel color
| ((color red))
| ((color blue))
| ((color green)))
|
|<... various compilation messages ...>
|
|YES.
|OK.
|
|==> (color ?x)
|
|?X = RED
KnowledgeWorks and Prolog User Guide (Unix version) - 26 Feb 2015