%0 Book Section
%T Extending OCL with Null-References
%A Brucker, Achim D.
%A Krieger, Matthias P.
%A Wolff, Burkhart
%E Gosh, Sudipto
%B Models in Software Engineering
%D 2009
%N 6002
%I Springer-Verlag
%C Heidelberg
%G USenglish
%F brucker.ea:ocl-null:2009
%O Selected best papers from all satellite events of the MoDELS 2009 conference.
%X From its beginnings, OCL is based on a strict semantics for undefinedness, with the exception of the logical connectives of type Boolean that constitute a three-valued propositional logic. Recent versions of the OCL standard added a second exception element, which, similar to the null references in object-oriented programming languages, is given a non-strict semantics. Unfortunately, this extension has been done in an ad hoc manner, which results in several inconsistencies and contradictions. In this paper, we present a consistent formal semantics (based on our HOL-OCL approach) that includes such a non-strict exception element. We discuss the possible consequences concerning class diagram semantics as well as deduction rules. The benefits of our approach for the specification-pragmatics of design level operation contracts are demonstrated with a small case-study.
%K HOL-OCL, UML, OCL, null reference, formal semantics
%U http://www.brucker.ch/bibliography/abstract/brucker.ea-ocl-null-2009
%U http://www.brucker.ch/bibliography/download/2009/brucker.ea-ocl-null-2009.pdf
%U http://dx.doi.org/10.1007/978-3-642-12261-3_25
%P 261-275