Improving Code Generation for Associations: Enforcing Multiplicity Constraints and Ensuring Referential Integrity

SERA 2013 (August 7, 2013 in Prague, Czech Republic)

Omar Badreddin, Andrew Forward, Timothy C. Lethbridge1 University of Ottawa

obadr024@uottawa.ca / oobahy@gmail.com aforward@site.uottawa.ca / aforward@gmail.comtcl@site.uottawa.cahttp://umple.org

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1

Overview• Umple Philosophy (Quick Review)• Umple Association Syntax• Umple in Academia and Industry• Getting Involved• Future Work

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Umple Philosophy

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Umple features can be created and viewed diagrammatically or textually

Umple extends a base language in a minimally invasive way

Intermediate generated code should not be edited

=Modeling is programming and vice versa

No round-trip engineering required

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Defining Association• Specification describing the links between objects that can

exist at run time

• Each end of the association has a multiplicity• Specifies upper and lower bound on the number of links

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class X { 0..1 -- * Y;}class Y {}

X can have many Y’s, and Y can optionally have one X.

Available Multiplicities

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Optional One / OneMany / Star

Umple Association Syntax

// Embed within the classclass X{ 0..1 -- * Y yonks;}

class Y {}

// Or Define explicitlyclass Z {}association m { * Z -> * Y; } 6

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Supports all multiplicities,e.g. 1, m..n, 1..*

To name an association (also optional) simply declare it explicitly as shown here.

Optionally name the association end for clearer intention as well as to support multiple associations between two classes.

Directed associations

Referential Integrity• Either side of the relationship can be set, and the other will

automatically be maintained, so

x.addY(y) equivalent to y.setX(x)

• If either side removes a relationship, then the other side will automatically be removed as well, so

y.setX(x1); // x1 associated with yy.setX(x2); // x1 unassociated with y

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Multiplicity Constraint• Set / Add / Remove might fail (returns a false) if the

multiplicity is not supported• Multiplicities also affect relationship (e.g. setting Y to a new X,

removes the old relationship because of the 0..1 multiplicity)

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Associations In Practice

• Too difficult to identify associations with any degree of certainty by looking only at the source code

• Difficulty with which we had trying to identify the use of association in code served as a motivation in itself

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Expl

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Mod

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ML

Attrib

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Analyzed Models Instead• 1400 Industry examples by looking at UML specs and UML

profiles• UML v1.5• UML v2.1.2• MARTE, Flow Composition, ECA, Java, Patterns, rCOS

• 98 Example models from a course textbook of one of the authors

• 250 Repository models from the collection of models codified in Umple

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Multiplicity Rankings inIndustrial Models

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One To Many Most Used In All Sources

Very few non one or many ends

Multiplicity Rankings inExample / Textbook Models

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Multiplicity Rankings inUML Repositories

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UML Repository viewable at http://try.umple.org

Code Generation for Associations in Existing Tools

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• All similar implementations, member variables for One multiplicities and List variables for Many

• Little to no referential integrity• Little to no multiplicity constraints

Association Combinations

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Bi-Directional Associations (between different classes)

Directed Associations* -> 0..1; -> 1; -> *; -> m..n; -> n; -> m..*; -> 0..n

Symmetric Associations (between the same class)• Reads the same in both directions (e.g. spouse)

A total of 42 different possible association types have been identified• 28 for bidirectional associations• 7 for unidirectional associations• 7 for symmetric associations

Each case explicitly handled, with code re-use where possible

Association Code Generation• Member variables for One• List variables for Many• Referential Integrity maintained

• E.g. a student switches mentors• Multiplicity Constraints enforced

• E.g. cannot overload a mentor

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class X { 0..1 -- * Y;}class Y {}

One Association-End

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Many Association-End

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Try For Yourself

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http://try.umple.org

Academic Use Of Umple

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Umple (metamodel.umple.org)

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Teaching Umple• University of Ottawa, Canada

• Second year Introduction to Software Engineering• Fourth year Advanced Design• Other professors, including at graduate level

• SCORE finalists at ICSE 2011• UCOSP (Undergraduate Capstone Open Source Project)

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Industry Examples

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hatchmortgage.com

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alms.arrowmight.ca

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arm.arrowmight.ca

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http://cruise.eecs.uottawa.ca/umpleonline/iframeexample.html

Embed Models In HTML

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<html><head><title>My Example</title></head><body><p> <iframe height=550 width=100% frameborder="0" scrolling="auto" src="http://try.umple.org/umple.php?example=2DShapes&readOnly&notext&nomenu&nochrome"><p>No iframe support</p></iframe></p>

<p> <iframe height=550 width=100% frameborder="0" scrolling="auto" src="http://try.umple.org/umple.php?example=2DShapes&readOnly&nodiagram&nomenu&nochrome"><p>No iframe support</p></iframe></p>

</body></html>

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Current and Future Work• Umplification

• Starting with OO code, incrementally add modeling abstractions• Maintain system functionality throughout the process• Using existing code repositories• Reduce code size

• Model Based Tracing• Define tracing directive at the model level

• Aspect Orientation• Additional Refactoring on Umple itself

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Getting Involved• Open source project: https://code.google.com/p/umple/• Teaching

• Use Umple to introduce UML and MDE.• Umplification

• Incrementally replace boilerplate code with modeling abstractions

• Lightweight Modeling and Analysis• Visualize Umple source as UML diagrams to analyze it

• Model driven development• Generate code in one of the supported base languages

• Rapid system prototyping

Comments and feedback: tcl@site.uottawa.ca30

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More information

• Publications on Umple:

https://code.google.com/p/umple/wiki/Publications

• The User Manual:

http://cruise.eecs.uottawa.ca/umple/GettingStarted.html

• Umple Home page: http://cruise.eecs.uottawa.ca/umple/

• Download Umple:

http://cruise.eecs.uottawa.ca/umpleonline/download_eclipse

_umple_plugin.html

• Report an issue:

https://code.google.com/p/umple/issues/entry

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Summary• 42 unique ways to define an association between one or two• In practice, mostly One or Many, but mostly does not mean

always• Implemented referential integrity and multiplicity constraints

for each unique combination• Test-Driven approach to reduce regressions• Important as new features are added to the languagethe help

reduce code clones• Many additional features available in Umple including tracing,

state machines, code injections, mixin• More coming including better support for aspect orientation

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