Towards SCM in Unified Modelspi.informatik.uni-siegen.de/CVSM2008/slides/koegel.pdf · • Model...

Technische Universität München

Towards SCM for Unified Models

Maximilian Kögel [email protected]

Technische Universität München Department for Informatics

Chair for Applied Software Engineering


Motivation

• Model Driven Development – Models exist and are maintained over extended periods of time – Models are designed collaboratively

• Unified Modeling – More and more tools and therefore models are integrated – Tracking evolution of intra-and-inter model links

17.05.2008 ICSE'08, CVSM: Towards SCM for Unified Models - M. Kögel 2



Unified Models



Traditional SCM approaches

• Impedance mismatch – complex graph of interrelated artifacts

vs. files and lines – configuration items: files vs. model elements – change granularity: line vs. model element attributes and graph structure

• Possible implementations – Graph is represented in one file:

• No meaningful change tracking (per element) • Frequent merges • Difficult to merge without destroying model integrity

– One file per model element: • Loss of semantic relationships of model elements • Model integrity cannot be preserved by SCM



Operation-based change tracking

• State-based deltas – Deltas calculated from two states – Expensive to perform for large and complex graphs – Difficult or impossible to recreate original changes

• Operation-based deltas – Deltas based on original sequence of editor operations – Editor must support capture of operations – Editor is coupled with SCM



Three layers of change

Logical Layer set of changes comprising logically coherent task

Meta Model Layer operations as defined by the meta model

clarify use case … …

add actor add step set name … …

create elem add link set field … …

Model Layer operations as defined by the domain models



Three Layers of change (cont.)



Version model

• Versions: v1.1, v1.2, v1.3 … • Change Packages: c1, c2, c2

v1.2 v1.3 v1.1

v2.1 v2.2

c1

c2

c3

variant of

revision of



Version model (class diagram)


Operation-based Diffing

• Version Model instances are trees • Collect ChangePackages on directed path from source to target version • Optional: Canonize changes (optional)

– One-pass in reverse order – Add Elements of Delete and Modify MetaModelOperations to set A – Remove all Modify MetaModelOperations referring to elements in set A – Remove empty ModelOperations


v1.2 v1.3 v1.1

v2.1 v2.2

c1

c2

c3



Operation-based Merging

• Merging is required if conflicts arise on update • Merging driven by conflict detection strategy:

– Defines transitive requires relation: A requires B – Defines conflicts relation: A conflicts B

• Merging algorithm: – Two lists of operations: mine, theirs – User must select operations to accept or reject – Case Accept Operation o in set mine:

• Find all required operations for o in mine (transitive closure) => set A • Find all operations in set theirs conflicting with set A => set B • Find all operations in theirs that require operations from B (transitive closure) => set C • Set A must be accepted if o is accepted • Set C must be rejected if o is accepted • Merge result (list of operations):

– Reversed list of all reversed operations in set C – List of all operations in A – Operation o



Example: Operation-based Merging

MyOperation1

MyOperation2

MyOperation3

TheirOperation1

TheirOperation2

TheirOperation3

TheirOperation4

TheirOperation4-1

TheirOperation3-1

TheirOperation1-1

MyOperation1

MyOperation3

My List: Merged List: Their List:


Prototype Implementation in Sysiphus (http://sysiphus.org)

• Use of prototype in project in collaboration with Airport Munich: – 40 Students – Real client, real problem, real data

• Change Tracking: – 54.000 changes on logical layer: change packages (and revisions) – 73.000 changes on model layer – 243.000 changes on meta model layer




Future research, next steps

• Evaluation: fine-grained vs. file-based change tracking

• Semantic operations – Define semantics of operations not only by its meta model operations – Result might depend on initial project state

• Integration of current research prototype with Eclipse EMF => More information on http://unicase.org



Questions? Discussion…

Towards SCM in Unified Modelspi.informatik.uni-siegen.de/CVSM2008/slides/koegel.pdf · • Model...

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