1. Jose E. Rivera, Antonio Vallecillo Universidad de Málaga, Spain TOOLS Europe 2008, Zurich

2. TOOLS Europe 2008(2)June 30, 2008  Model-Driven Software Development (MDSD) ● Models are the key artifacts ● Most of the efforts are currently on the definition of models, metamodels and transformations between them ● Other model operations (e.g., model subtyping, model difference) are required in MDSD practices  Model difference ● An essential operation in several software development processes:  Version and change management  Software evolution  Model/data integration  etc.

3. TOOLS Europe 2008(3)June 30, 2008  Previous approaches: ● Edit scripts and coloring techniques:  Do not produce models as results  Do not fulfill other interesting properties (composability…) ● Based on text, data structures or models  Usually restricted to a specific metamodel (UML)  Our approach: ● Model-based:  Differences are models, conforming to a metamodel ● Metamodel independent ● Self-contained, compact, composable, applicable to models conforming to different metamodel ● Implementation available integrated in EclipseMAUDELING

4. TOOLS Europe 2008(4)June 30, 2008 1) Matching ● Finding different objects from the two models that represent the same element ● The result is a model: 2) Differencing ● Makes use of matching models to detect modified elements ● The result is a model: Benefits: Self-contained Compact Independent of the metamodel of the source models

5. TOOLS Europe 2008(5)June 30, 2008  Option 1: Using object persistent identifiers Matching process is simple and robust  But not always feasible!  Option 2: Using structural similarities Allows comparing models…  that do not use persistent object identifiers  conforming to different metamodels  that have evolved independently  Harder to define and implement  You need an algorithm to identify the matches

6. TOOLS Europe 2008(6)June 30, 2008  Compares objects independently of their depth in the containment tree ● Implies more comparisons ●...but brings very interesting advantages:  Moved elements through different levels can be detected;  Example of refactorization-> adding packages  Failing to identify a match does not condition other potential matches below in the tree hierarchy  Implemented in MaudeMAUDELING

7. TOOLS Europe 2008(7)June 30, 2008  Comparing two objects: ● Class rate: ● Name rate:

8. TOOLS Europe 2008(8)June 30, 2008  Structural rate depends on the type of the feature ● Boolean attributes and enumerations match (with rate = 1.0) if they have the same value (otherwise rate = 0.0) ● String attribute values distances are calculated using the Levenshtein distance ● Numerical attribute values match rate is computed with a relative distance function (1-|n-m|/|n+m|) limited to [0..1] ● References are matched recursively, i.e., objects referenced are compared using the same match operation but without taking into account their own references (to avoid cycles)  If the upper cardinality is greater than 1 (i.e., if its value is a collection), the average rate is calculated  If a structural feature is defined only in one of the objects, a penalty is applied to the final sfRate

9. TOOLS Europe 2008(9)June 30, 2008  If (Rate > Threshold) the two objects potentially match  Initially considered (although it is fully configurable):  wc = 0.5; wsf = 0.25; wn = 0.0; Threshold = 0.66  nameRate is used in models in which the attribute name is considered as an identifier. ● If the name rate is omitted (wn=0.0), potential matches are harder: features should be more strongly related  At the end of the process, only those objects that together obtain the biggest rate are kept

10. TOOLS Europe 2008(10)June 30, 2008  Formal notation and system ● High-level language and a high-performance interpreter and compiler of the OBJ algebraic specification family ● Supports membership equational and rewriting logic specification and programming ● Maude specifications are executable  Supported by a toolkit ● Executing the specifications, model-checking, theorem proving, termination and confluence, etc.  Highly efficient and integrated with Eclipse

11. TOOLS Europe 2008(11)June 30, 2008  Maude supports OO specifications and computations ● Classes: class C | a1 : S1, …., an : Sn ● Objects: ● Messages: msg m : S1 … Sn -> Msg. ● A configuration is a multiset of objects and messages that evolves by rewriting rules  Models are represented as configuration of objects Nodes Nodes’ attributes Nodes’ Edges Objects Objects’ attributes Multigraph Maude Configuration of objects

12. TOOLS Europe 2008(12)June 30, 2008  Object-oriented modules (i.e., specifications) ● They contain the classes to which the Maude objects belong ● Models conform to metamodels by construction ● Used to instantiate models, to add behavior…  Metamodels are models too! ● They can be represented as Configuration of objects  The classes of such objects will be the ones that specify the meta-metamodels (for example Ecore)  Used to operate and reason about them

13. TOOLS Europe 2008(13)June 30, 2008 (omod SimpleStateMachines is pr STRING. class State | name : String, stateMachine : Oid, incoming : Set{Oid}, outgoing : Set{Oid}. class StateMachine | initialState : Maybe{Oid}, containedState : Set{Oid}. class Transition | name : String, target : Oid, src : Oid. endom)  Simple State Machine example membership axioms Conforms to +

14. TOOLS Europe 2008(14)June 30, 2008 op modelDiff : Configuration Configuration -> DiffModel.  Possible situations : ● The element appears in both models and has not been modified ● The element appears in both models but has been modified; ceq modelDiff( CONF1> CONF2, MATCHM) = modelDiff(CONF1, CONF2, MATCHM) if match(O1, O2, MATCHM). ceq modelDiff( CONF1, CONF2, MATCHM) = modelDiff(CONF1,CONF2,MATCHM) if match(O1, O2, MATCHM) /\ (not(ATTS1 == ATTS2) or not(C1 == C2)).

15. TOOLS Europe 2008(15)June 30, 2008 ● The element only appears in the minuend model; ● The element only appears in the subtrahend model. ● Both the minuend and subtrahend models are empty: eq modelDiff( CONF1, CONF2, MATCHM ) = modelDiff(CONF1, CONF2, MATCHM) [owise]. eq modelDiff( CONF1, CONF2, MATCHM ) = modelDiff(CONF1, CONF2, MATCHM) [owise]. eq modelDiff( none, none, MATCHMODEL ) = none.

16. TOOLS Europe 2008(16)June 30, 2008 (Minuend Model) (Subtrahend Model) Tr2 (Difference Model)

17. TOOLS Europe 2008(17)June 30, 2008  Operation do ● do ( Ms, Md ) = Mm. ● Applies to a model all the changes specified in a difference model  Operation undo ● undo ( Mm, Md ) = Ms. ● Reverts all the changes specified in a difference model  Sequential composition of differences ● Very useful to, e.g., optimize the process of applying successive modifications to the same model undo(do(Ms, Md), Md) = Ms. do(undo(Mm, Md), Md) = Mm.

18. TOOLS Europe 2008(18)June 30, 2008 op do : Configuration DiffModel -> Configuration. eq do ( MODEL, CONF ) = do ( MODEL, CONF ). ceq do ( MODEL, CONF ) = do ( MODEL, CONF ) if O = originalId(OLDO). ceq do ( MODEL, CONF ) = do(MODEL, CONF) if O = originalId(OLDO). eq do ( MODEL, none ) = MODEL.

19. TOOLS Europe 2008(19)June 30, 2008  Model difference definition ● Independent of the metamodel of the source models ● Can be fully integrated into other MDSD processes ● Self-contained and compact ● Applicable to models conforming to different metamodel ● Suitable for composing deltas and implementing further operations on them ● Results are very encouraging  Tool support: ● All the difference operations implemented in Maude ● Integrated in EclipseMAUDELING

20. TOOLS Europe 2008(20)June 30, 2008  Make Maude completely transparent to the user  Conflict detection and resolution of concurrent modifications  Improving the matching algorithm ● More complex heuristics ● More customizable parameters  Make model operations available via Web services