TY - CHAP AU - Brucker, Achim D. AU - Krieger, Matthias P. AU - Wolff, Burkhart ED - Gosh, Sudipto PY - 2009 DA - 2009// TI - Extending OCL with Null-References BT - Models in Software Engineering T3 - Lecture Notes in Computer Science SP - 261 EP - 275 IS - 6002 PB - Springer-Verlag CY - Heidelberg KW - HOL-OCL, UML, OCL, null reference, formal semantics AB - 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. L1 - https://www.brucker.ch/bibliography/download/2009/brucker.ea-ocl-null-2009.pdf UR - https://www.brucker.ch/bibliography/abstract/brucker.ea-ocl-null-2009 UR - https://doi.org/10.1007/978-3-642-12261-3_25 DO - 10.1007/978-3-642-12261-3_25 LA - USenglish N1 - Selected best papers from all satellite events of the MoDELS 2009 conference. ID - brucker.ea:ocl-null:2009 ER -