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Extending OCL with Null-References

by Achim D. Brucker, Matthias P. Krieger, and Burkhart Wolff

Cover for brucker.ea:ocl-null:2009.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.

Keywords: HOL-OCL, UML, OCL, null reference, formal semantics
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QR Code for brucker.ea:ocl-null:2009.Please cite this article as follows:
Achim D. Brucker, Matthias P. Krieger, and Burkhart Wolff. Extending OCL with Null-References. In Models in Software Engineering. Lecture Notes in Computer Science (6002), pages 261-275, Springer-Verlag, 2009. Selected best papers from all satellite events of the MoDELS 2009 conference.
Keywords: HOL-OCL, UML, OCL, null reference, formal semantics
(full text as PDF file) (BibTeX) (Endnote) (RIS) (Word) (doi:10.1007/978-3-642-12261-3_25) (Share article on LinkedIn. Share article on CiteULike. )

BibTeX
@InCollection{ brucker.ea:ocl-null:2009,
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.},
address = {Heidelberg},
author = {Achim D. Brucker and Matthias P. Krieger and Burkhart Wolff},
bibkey = {brucker.ea:ocl-null:2009},
booktitle = {Models in Software Engineering},
doi = {10.1007/978-3-642-12261-3_25},
editor = {Sudipto Gosh},
keywords = {HOL-OCL, UML, OCL, null reference, formal semantics},
language = {USenglish},
location = {Denver, Colorado, USA},
note = {Selected best papers from all satellite events of the MoDELS 2009 conference.},
number = {6002},
pages = {261--275},
pdf = {https://www.brucker.ch/bibliography/download/2009/brucker.ea-ocl-null-2009.pdf},
publisher = {Springer-Verlag},
series = {Lecture Notes in Computer Science},
title = {Extending OCL with Null-References},
url = {https://www.brucker.ch/bibliography/abstract/brucker.ea-ocl-null-2009},
wsbooktitle = {The Pragmatics of OCL and Other Textual Specification Languages},
year = {2009},
}