OCL By Example Lecture - TUD - TU Dresden - Startseite - Aktuelles

60 Pages·2009·0.68 MB·English

Department of Computer Science, Institute for Software and Multimedia Technology
OCL
((OObbjjeecctt CCoonnssttrraaiinntt LLaanngguuaaggee))
by Example
DDrr. BBiirrggiitt DDeemmuutthh
In theory, there is no difference
between theory and practice.
But, in practice, there is.
Jan L. A. van de Snepscheut/Yogi Bera
Dr. Birgit Demuth MINE Summer School, Nida, 2009 2
Main Goals of the Lecture
• Bridge the gap between practically used software
specifications (UML) and formal languages
• IInnttrroodduuccee iinnttoo OOCCLL ((hhiissttoorryy, oouuttlliinnee, lliitteerraattuurree))
• Learn how to specify semantics using OCL
• LLeeaarrnn wwhhaatt aarree iinntteerreessttiinngg OOCCLL uussee ccaasseess
• Inform what OCL tools can already be used
Dr. Birgit Demuth MINE Summer School, Nida, 2009 3
Foundation: Assertions
• An assertion is a predicate (i.e., a true–false statement)
placed in a program to indicate that the developer thinks
tthhatt tthhe preddiicatte iis allways ttrue att tthhatt pllace [[WWiikkiipeddiia]].
• Usagge in
– Hoare logic [Hoare 1969]
– Design by contract [Meyer 1986, Eiffel]
– FFoorr rruunn-ttiimmee cchheecckkiinngg ((JJaavvaa ((assertt)), JJMMLL, JJAASSSS, SSQQLL,
…)
– During the development cycle (debugging)
– Static assertions at compile time
Dr. Birgit Demuth MINE Summer School, Nida, 2009 4
Object Constraint
• Model-based assertion
• [[Warmer andd Klleppe]] ddeffine a constraint as ffollllows:
“AA ccoonnssttrraaiinntt iiss aa rreessttrriiccttiioonn oonn oonnee oorr mmoorree vvaalluueess
of (part of) an object-oriented model or system.“
• OCL as specification language for object constraints
Dr. Birgit Demuth MINE Summer School, Nida, 2009 5
History of OCL
• Developed at IBM in 1995 originally as a business
engineering language
• AAddoopptteedd aass aa ffoorrmmaall ssppeecciiffiiccaattiioonn llaanngguuaaggee wwiitthhiinn UUMMLL
• Part of the official OMG standard for UML (from
version 1.1 on)
• Used for precisely defining the well-formedness rules
(WFRs) for UML and further OMG-related metamodels
•• CCuurrrreenntt vveerrssiioonn iiss OOCCLL 22.00
Dr. Birgit Demuth MINE Summer School, Nida, 2009 6
OCL (Object Constraint Language)
• Extends the Unified Modeling Language (UML)
• FFoorrmmaall llaanngguuaaggee ffoorr tthhee ddeeffiinniittiioonn ooff ccoonnssttrraaiinnttss aanndd
queries on UML models
• Declarative
• SSidde effffect ffree
• Add precise semantics to visual (UML-) models
•• GGeenneerraalliizzeedd ffoorr aallll MMOOFF bbaasseedd mmeettaammooddeellss
• Meanwhile generally accepted
• Many extensions such as for temporal constraints
• „Core Language“ of other OMG languages (QVT, PRR)
Dr. Birgit Demuth MINE Summer School, Nida, 2009 7
Literature
[[1]] Warmer,, J.,, Kleppppe,, A.: The Objject Constraint Langguagge.
Precise Modeling with UML. Addison-Wesley, 1999
[2] Warmer, J., Kleppe, A.: The Object Constraint Language
SSeeccoonndd EEddiittiioonn..
Getting Your Models Ready For MDA. Addison-Wesley, 2003
[3] OMG UML specification,
wwwwww..oommgg..oorrgg//tteecchhnnoollooggyy//ddooccuummeennttss//mmooddeelliinngg_ssppeecc_ccaattaalloo
g.htm#UML
[4] OMG UML 2.0 OCL,
wwwwww.oommgg.oorrgg//tteecchhnnoollooggyy//ddooccuummeennttss//ffoorrmmaall//ooccll.hhttmm
[5] Heinrich Hußmann: Formal Specification of Software
Systems. Course, 2000, Technische Universität Dresden
Dr. Birgit Demuth MINE Summer School, Nida, 2009 8
Dr. Birgit Demuth MINE Summer School, Nida, 2009 9
Constraint
Definition
– „A constraint is a restriction on one or more
values of (part of) an object-oriented model or
ssyysstteemm.“
• A constraint is formulated on the level of classes, but
its semantics is applied on the level of objects.
• originally formulated in the syntactic context of a UML
UUMMLL mmooddeell ((ii.ee. aa sseett ooff UUMMLL ddiiaaggrraammss))
Dr. Birgit Demuth MINE Summer School, Nida, 2009 10