UML is still inconsistent! How to im prove OCL Constraints in the - - PowerPoint PPT Presentation

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UML is still inconsistent! How to im prove OCL Constraints in the - - PowerPoint PPT Presentation

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Departm ent of Com puter Science Institute for Software and Multimedia Engineering, Software Technology Group UML is still inconsistent! How to im prove OCL Constraints in the UML 2 .3 Superstructure Claas Wilke and Birgit Demuth OCL 2011

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SLIDE 1

UML is still inconsistent!

How to im prove OCL Constraints in the UML 2 .3 Superstructure Claas Wilke and Birgit Demuth

Departm ent of Com puter Science Institute for Software and Multimedia Engineering, Software Technology Group

OCL 2011 Zurich, June 29th 2011

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Motivation

  • OCL usage w ithin the UML specification
  • Definition of constraints
  • Definition of addititonal operations
  • W hen UML w as originally specified, no OCL tooling existed

→ OCL rules where specified manually („by hand“) → No checks of syntax and static semantics

  • I nvestigations on UML/ OCL inconsistency
  • UML 2.0: 361 errors in 246 OCL rules [ BGG04]
  • UML 1.5: 450 errors [ FQL+ 03]
  • UML 1.3: 39 errors in 71 OCL rules [ RG00]
  • This w ork
  • Today‘s situation (UML 2.3)?
  • How can similar problems avoided for future specifications?

Zurich, June 29th 2011 UML is still inconsistent! Slide 2

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SLIDE 3

Methodology (1/ 2)

Zurich, June 29th 2011 UML is still inconsistent! Slide 3

UML 2.3 Superstructure MDT UML 2.3 Metamodel copy / paste import Dresden OCL Parser/ Editor errors / warnings manual investigation / modification / classification Project online at http:/ / w w w .dresden-ocl.org/ index.php/ DresdenOCL:W FRsI nUML

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Methodology (2/ 2)

  • Only OCL expressions from constraints sections investigated
  • Additional operations (body expressions) ignored
  • Context declarations were added manually
  • Textual constraints w ere counted
  • Neither transformed into OCL
  • Nor checked if that is possible at all
  • Erroneous constraints w ere fixed w here possible
  • Sam e error occuring m ultiple tim es in one constraint
  • Counted as one error

Zurich, June 29th 2011 UML is still inconsistent! Slide 4

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Results

  • 4 6 .8 % of all constraints have no OCL sem antics!
  • 4 8 .5 % of all OCL rules are erroneous!

Zurich, June 29th 2011 UML is still inconsistent! Slide 5

General Statistics

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Results

  • Total: 3 2 0 errors
  • Classified into 1 4 types of five categories

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Different Types of Errors

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Results

1 . Typing Errors 15 (6.4 % ) 2 . Brackets 27 (11.5 % ) 3 . W rong I fs 8 (3.4 % ) 4 . Missing Escape 14 (6.0 % ) 5 . W rong use of # 6 (2.6 % ) 6 . W rong use of -> / . 9 (3.8 % )

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Syntactical Errors

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Results

1 . W rong Nam edElem ent Referred 62 (26.4 % ) 2 . Operation vs. Property Call 9 (3.8 % )

Zurich, June 29th 2011 UML is still inconsistent! Slide 8

Minor I nconsistencies

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3 . Missing asSet( ) 15 (6.4 % ) 4 . Missing asOrderedSet( ) 9 (3.8 % ) 1 . Result Type 20 (8.5 % ) 2 . W rong I terator 4 (1.7 % )

Results

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Type Checking Errors

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SLIDE 10

1 . Enum eration Literals 54 (23.0 % ) 2 . Set{ } vs. null 16 (6.8 % )

Results

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Evolution Errors

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SLIDE 11

1 . I m plicit asSet 94 2 . I m plicit collect 18

Results

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I m plicit Conversions

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  • The OCL rule quality has not been im proved since [ BBG0 4 ] !
  • The current specification approach is insufficient
  • 1. No syntactical checks
  • 2. No static semantics checks
  • 3. No dynamic semantic checks
  • 4. No Support for UML/ OCL coevolution
  • Proposed specification im provem ents
  • 1. Model-Based Specification process
  • 2. Elucidative Specification
  • 3. Use of OCL unit testing
  • 4. Use of UML/ OCL coevolution tools
  • Proposed OCL im provem ents
  • 1. Removal of -> operator
  • 2. Avoidance of implicit conversions
  • 3. Introduction of selectByKind()

Lessons Learnt

Zurich, June 29th 2011 UML is still inconsistent! Slide 12

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[ WBS+ 11]

Possible Improvements

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Elucidative Specification

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  • The -> operator for collection operations is irritating
  • Even authors of UML do not know how to use it
  • Using w rong operators is dangerous
  • Different semantics
  • Unnecessary conversions

→ Use . for collection operations as w ell

Possible Improvements

Zurich, June 29th 2011 UML is still inconsistent! Slide 14

Rem oval of the -> operator

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SLIDE 15
  • I m plicit conversions often occur unforeseen
  • Dangerous and unnecessary com binations possible

→ They should be avoided, if not forbidden

Possible Improvements

Zurich, June 29th 2011 UML is still inconsistent! Slide 15

Avoid im plicit asSet and im plicit collect

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Summary

  • I nvestigation of OCL rules defined in UML
  • 53.2 constraints do not define any OCL rules
  • 48.5% of all OCL rules contain errors
  • Many errors could be avoided
  • Improved specification process
  • Modifications of the OCL
  • Future W ork
  • Do other specifications have the same problems?
  • Are proposed improvements applicable
  • How did existing UML implementations solved the OCL errors?

Zurich, June 29th 2011 UML is still inconsistent! Slide 16

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Literature (1/ 2)

[ BGG04] H. Bauerdick, M. Gogolla, F. Gutsche. Detecting OCL Traps in the UML 2.0 Superstructure: An Experience Report. In: UML 2004 - The Unified Modeling Language. LNCS 3273, pp. 188-196. Springer Berlin / Heidelberg, 2004. [ FQL+ 03] J. Fuentes, V. Quintana, J. Llorens, G. Genova,

  • R. Prieto-Daz. Errors in the UML metamodel? ACM SIGSOFT

Software Engineering Notes 28(6), 2003. [ RG00]

  • M. Richters, M. Gogolla. Validating UML Models and OCL
  • Constraints. In: Proceedings of the 3rd international

conference on The unified modeling language: advancing the standard, pp. 265-277. Springer Berlin / Heidelberg, 2000. [ CO09]

  • J. Chimiak-Opoka. OCLLib, OCLUnit, OCLDoc: Pragmatic

Extensions for the Object Constraint Language. In: Model Driven Engineering Languages and Systems. LNCS 5795,

  • pp. 665–669. Springer Berlin / Heidelberg, 2009.

Zurich, June 29th 2011 UML is still inconsistent! Slide 17

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Literature (2/ 2)

[ HG10]

  • L. Hamann, M. Gogolla. Improving Model Quality by

Validating Constraints with Model Unit Tests. In: Proceedings

  • f the Models Workshop on Model-Driven Enginering,

Verification and Validation (MoDeVVa2010). 2010. [ WBS+ 11] C. Wilke, A. Bartho, J. Schroeter, S. Karol, U. Aßmann. Elucidative Specification of the Unified Modeling Language. Submitted for the ACM/ IEEE 14th International Conference

  • n Model Driven Engineering Languages and Systems

(MODELS 2011), Wellington, New Zealand, October 16 - 21, 2011.

Zurich, June 29th 2011 UML is still inconsistent! Slide 18

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Thank you!

Dresden OCL http:/ / w w w .dresden-ocl.org/ Softw are Technology Group http:/ / st.inf.tu-dresden.de/ QualiTune http:/ / w w w . qualitune.org/ claas.w ilke@tu-dresden.de

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Backup

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Results

→ Most OCL rules are rather sim ple

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OCL Rule Com plexity ( structure)

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  • Testing OCL constraints is sensible
  • Do they constrain what they shall constrain?
  • Checks for runtime errors (invalid values)

E.g., division by zero

  • OCL testing facilities exist
  • [ CO09] , [ HG10]
  • Unit tests could be deployed together w ith the specification
  • Regression/ acceptance tests for UML case tools

Possible Improvements

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OCL Unit Testing

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  • A select is often follow ed by a cast
  • Filter → Cast
  • Requires two iterations → overhead
  • I ntroduction of a selectByKind iterator

→ Only one iteration remaining

  • And even more readable

Possible Improvements

Zurich, June 29th 2011 UML is still inconsistent! Slide 23

I ntroduction of selectByKind iterator