Larch/Smalltalk is a behavioral interface specification language for Smalltalk-80.
An overview of Larch/Smalltalk is contained in the following papers.
You might also want to look at the book J.V. Guttag and J.J. Horning, Larch: Languages and Tools for Formal Specification, (Springer-Verlag, 1993), to see more details on the Larch approach to specification.
You may also want tools for the Larch Shared Language (LSL). These can be obtained by anonymous ftp from larch.lcs.mit.edu in the directory pub/Larch.
There is a global home page for Larch.
Graduate student Yoonsik Cheon (firstname.lastname@example.org) is the main designer of Larch/Smalltalk. He works with Gary T. Leavens.
Larch/Smalltalk was funded in part by NSF grant CCR-9593168.