Luckily Common Lisp already has ways to do that: Functions have defined keyword argument lists and can have type declarations which for example a compiler like

Luckily Common Lisp already has ways to do that: Functions have defined keyword argument lists and can have type declarations which for example a compiler like SBCL can partially check at compile-time. Common Lisp uses for anything more complex than lists of keyword value combinations CLOS classes, which form a multiple inheritance hierarchy and types for slots. That way I can look into a debugger at runtime and see what functions are actually supposed to receive and what these collects of keyword/value maps actually mean (since they are CLOS classes). Having simple lists as maps was popular with assoc lists in the 70s - basically the same as hash tables, but slower. Then lots of dynamic object systems were developed which were in essence dynamic key/value sets. Later various object systems appeard, with CLOS as a local maximum. Where Rich Hickey points to RDF, there is a lot prior art in Lisp as well -> Frame systems / description logics / .... http://wilbur-rdf.sourceforge.net/docs/ivanhoe.html http://wilbur-rdf.sourceforge.net/docs/ivanhoe.html http://franz.com/agraph/racer/krss-spec.pdf http://franz.com/agraph/racer/krss-spec.pdf and zillion others CLIM, the Common Lisp interface manager, uses 'presentation types' to specify user level data structures...