To ensure correct semantics in the context of multiple modules, some predicates are subject to module name expansion. Clauses or directives containing goals for such predicates need to have certain arguments annotated by a module prefix. A declaration:
:- meta_predicate :MetaPredSpec, ..., :MetaPredSpec.
where each MetaPredSpec is a skeletal goal, informs the compiler which predicates and which of its arguments should be subject to such annotations. See ref-mod-met and ref-mod-mne for details.