@InCollection{	  brucker.ea:ocl-null:2010,
  author	= {Achim D. Brucker and Matthias P. Krieger and Burkhart
		  Wolff},
  wsbooktitle	= {The Pragmatics of OCL and Other Textual Specification
		  Languages},
  note		= {Selected best papers from all satelite events of the
		  MoDELS 2009 conference.},
  booktitle	= {Models in Software Engineering},
  publisher	= {Springer-Verlag},
  address	= {Heidelberg},
  series	= {Lecture Notes in Computer Science},
  number	= {6002},
  editor	= {Sudipto Gosh},
  pages		= {251--275},
  doi		= {10.1007/978-3-642-12261-3_25},
  language	= {USenglish},
  title		= {Extending OCL with Null-References},
  year		= {2010},
  classification= {workshop},
  categories	= {holocl},
  location	= {Denver, Colorado, USA},
  areas		= {formal methods, software},
  public	= {yes},
  abstract	= {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.},
  bibkey	= {brucker.ea:ocl-null:2010},
  pdf		= {http://www.brucker.ch/bibliography/download/2010/brucker.ea-ocl-null-2010.pdf},
  ps		= {http://www.brucker.ch/bibliography/download/2010/brucker.ea-ocl-null-2010.ps.gz},
  keywords	= {HOL-OCL, UML, OCL, null reference, formal semantics},
  url		= {http://www.brucker.ch/bibliography/abstract/brucker.ea-ocl-null-2010}
		  
}