Achim D. Brucker Burkhart Wolff A Proposal for a Formal OCL Semantics in Isabelle/HOL. 99-114 2002 conf/tphol/2002 TPHOLs http://link.springer.de/link/service/series/0558/bibs/2410/24100099.htm db/conf/tphol/tphol2002.html#BruckerW02