Dear Paulo,

Possible outputs of predicate_property/2 predicate are:

interpreted: Predicate is currently interpreted (because it is loaded in debug mode or it is dynamic) compiled: Predicate is not interpreted dynamic: Predicate is dynamic (or data) concurrent: Predicate is to be used as data interchange among concurrent threads wait: Predicate is blocking (in development) multifile: Predicate is multifile

On the other hand, as predicate_property/2 is provided to access internal information, the format of the first argument is a bit odd: to know about predicate foo/2 in module bar, you have to write 'bar:foo'(_,_) (this may change in next versions).

Thus, the goal predicate_property(P,dynamic) succeeds only if P (in the above format) exists and is dynamic.

Regarding whether a given predicate is built-in is a more involved question, at least in Ciao. Almost all predefined predicates in Ciao can be redefined, and even using package 'pure' you can undefine all of them (except control constructs '->', ';', '!', etc). Anyway, if you tell me what is exactly your idea of "built-in predicate" and/or for what purpose do you need to know which predicates are so, perhaps I can find a hacking to find it out.