Larch
The Larch Project develops aids for formal specifications.
Each Larch specification has two components: an interface
containing predicates written in the LIL ({Larch Interface
Language}) designed for the target language and a 'trait'
containing assertions about the {predicate}s written in LSL,
the {Larch Shared Language} common to all.
["The Larch Family of Specification Languages", J. Guttag et
al, IEEE Trans Soft Eng 2(5):24-365 (Sep 1985)].