1. Daniel Amyot and Jun Biao Yan
Flexible Verification of User-Defined Semantic Constraints in Modelling Tools
Daniel Amyot and Jun Biao Yan
CASCON, October 28, 2008

2. Overview Motivations Tool Requirements
Illustration with a URN Tool: jUCMNav
Applications
Related Work, Conclusions and Future Work
URN and jUCMNav, CASCON Workshop, 2008 p. 2

3. Why Constraints? Person
Name
Gender
biologicalFather
0..1
0..*
child
The syntax of modelling languages is not always sufficient to describe user models precisely
Can we ensure the biological father of a person is a male?
URN and jUCMNav, CASCON Workshop, 2008 p. 3

4. Constraints in Metamodels?
Class
Name
superClass
0..1
0..*
subClass
Similar needs for metamodels, which define modelling languages such as UML, BPMN, URN…
Can we prevent circular relationships in class inheritance?
Can we enforce uniqueness of names in a given scope?
URN and jUCMNav, CASCON Workshop, 2008 p. 4

5. Semantic Constraints Provide precision in language definitions
“Well-formedness” of models
Can be expressed in many ways
e.g. with the Object Constraint Language (OCL)
Typically, semantic constraints are provided with the language
Tools can verify them
URN and jUCMNav, CASCON Workshop, 2008 p. 5

6. User-Defined Semantic Constraints
Not provided in the definition of a language
Needed to better support:
Different modelling styles and standards
Checking inputs to analysis algorithms
Verifying (cumulative) assumptions on chains of transformation tools, for interoperability
Such constraints vary from models to models, and their relevance may vary over time
Modelling tools must offer flexible and usable mechanisms for the verification of customizable semantic constraints.
URN and jUCMNav, CASCON Workshop, 2008 p. 6

7. Overview Motivations Tool Requirements
Illustration with a URN Tool: jUCMNav
Applications
Related Work, Conclusions and Future Work
URN and jUCMNav, CASCON Workshop, 2008 p. 7

8. Tool Requirements (I) Goals: Flexibility, Usability, Scalability
The tool shall
allow users to create, modify, and delete constraints, without having to recompile or restart
report constraints syntax errors
allow users to enable and disable individual constraints
verify, upon the user’s request, all enabled constraints on the model
URN and jUCMNav, CASCON Workshop, 2008 p. 8

9. Tool Requirements (II)
The tool shall
report constraint violations to the user
allow loading & saving constraints (for sharing & updates)
allow users to create, modify, and delete groups of constraints.
allow users to add/remove a constraint to/from one or many groups.
allow users to enable and disable groups of constraints
URN and jUCMNav, CASCON Workshop, 2008 p. 9

10. Overview Motivations Tool Requirements
Illustration with a URN Tool: jUCMNav
Applications
Related Work, Conclusions and Future Work
URN and jUCMNav, CASCON Workshop, 2008 p. 10

11. User Requirements Notation - URN
Graphical language standardized by ITU-T
Supports goal and scenario modelling
Goal-oriented Requirement Language (GRL)
Use Case Map (UCM) notation
Defined by a metamodel
(More in workshop on Wednesday afternoon)
URN and jUCMNav, CASCON Workshop, 2008 p. 11

12. jUCMNav: URN Editor
URN and jUCMNav, CASCON Workshop, 2008 p. 12

13. EMF-Based Implementation Metamodel
URN and jUCMNav, CASCON Workshop, 2008 p. 13

14. Groups and Constraints in Preferences
URN and jUCMNav, CASCON Workshop, 2008 p. 14

15. Constraint Structure Name Context (e.g. Package::ClassName)
OCL query expression
returns a sequence of objects of the type specified in the rule context.
OCL constraint expression (invariant to be verified)
Description (also used as error message)
Enabling indicator
Utility definitions (simplify invariant logic, optional)
URN and jUCMNav, CASCON Workshop, 2008 p. 15

16. Constraints Definition (with MDT-OCL)
URN and jUCMNav, CASCON Workshop, 2008 p. 16

17. Violations Reported in Problems View
URN and jUCMNav, CASCON Workshop, 2008 p. 17

18. Overview Motivations Tool Requirements
Illustration with a URN Tool: jUCMNav
Applications
Related Work, Conclusions and Future Work
URN and jUCMNav, CASCON Workshop, 2008 p. 18

19. Language and Style Compliance
Modelling tools deviate from standards… Extended subsets!
For example, for jUCMNav
jUCMNav implements a subset of the “standard” URN
jUCMNav extends URN with KPI and AoURN
Define constraints to verify that extension are not used in a given URN model
URN’s GRL builds on the i* framework
Define constraints to restrict the usage of GRL to an i* style
Appearance of diagrams
Define constraints to prevent certain colours in GRL diagrams reserved for analysis results (green, yellow, red)
URN and jUCMNav, CASCON Workshop, 2008 p. 19

20. Analysis of Models
Analysis procedures make assumptions about input models!
Might be cheaper to define constraints externally to the analysis procedure
For example:
URN allows for structural alternatives to be explored in a model Inconsistencies in the use of components are allowed across UCM diagrams
Define constraints to detect such inconsistencies when undesirable by an analysis procedure
Some completeness aspects of a model could be analysed directly using semantic constraints
jUCMNav allows modellers to create traceability links between GRL goals and UCM scenarios.
Define constraints to detect the absence of links for specific types of elements
URN and jUCMNav, CASCON Workshop, 2008 p. 20

21. Transformation of Models
Semantic constraints can act as large-scale preconditions to ensure a model is compatible with a transformation algorithm
Possibly cheaper than running a complex transformation to realize the model was not as expected
More importantly: Constraints accumulate when we start combining transformations in sequence!
URN and jUCMNav, CASCON Workshop, 2008 p. 21

22. Transformation of Models
Define constraints to check that important elements (e.g. actors, responsibilities) have non-empty descriptions
URN and jUCMNav, CASCON Workshop, 2008 p. 22

23. Transformation of Models
Constraints to check proper use of metadata in UCM responsibilities
Further constraints…
Further constraints…
URN and jUCMNav, CASCON Workshop, 2008 p. 23

24. Overview Motivations Tool Requirements
Illustration with a URN Tool: jUCMNav
Applications
Related Work, Conclusions and Future Work
URN and jUCMNav, CASCON Workshop, 2008 p. 24

25. Related Work
General Modeling Environment (GME) and Generic Eclipse Modeling System (GEMS)
OCL at model and metamodel levels
Sophisticated constraint manager
MOMENT-OCL
EMF Validation Framework
Better start point for implementing our approach
Support for live constraints (on-the-fly evaluation)
URN and jUCMNav, CASCON Workshop, 2008 p. 25

26. Conclusions
Need for flexible and usable mechanisms for the verification of customizable semantic constraints in modelling tools
Requirements and proof of concept with URN/jUCMNav
Applications to modeling styles, inputs of analysis algorithms, and preconditions on chains of transformation tools
Approach independent from target modelling language, constraint language, and implementation frameworks, but works well with EMF and OCL!
URN and jUCMNav, CASCON Workshop, 2008 p. 26

27. Future Work Is the approach beneficial? Empirical studies are needed…
Is the approach usable?
Knowledge of OCL and of the modelling language’s metamodel is required to create constraints…
Partial generation of OCL query expressions from metamodel
Use to define customizable metrics on models (queries)
URN and jUCMNav, CASCON Workshop, 2008 p. 27

28. URN Virtual Library: http://www.UseCaseMaps.org/pub/
For More Information
URN Virtual Library:
Over 210 papers and theses
jUCMNav:
URN and jUCMNav, CASCON Workshop, 2008 p. 28