1. Higher-Order Transformation Eugene SyrianiandHans Vangheluwe

2. Higher-Order Transformation Outline 1.What is a Higher-Order Transformation (HOT)? 2.Uses of HOT 3.Precise Modelling of Transformations 4.HOT in action 2

3. Higher-Order Transformation 1 What is a Higher-Order Transformation (HOT)? “A higher-order transformation is a model transformation such that its input and/or output models are themselves transformation models.” [Tisi09] At least one of the input or output artefacts of the HOT must be a transformation model. Transformation model  Transformation model Model*  Transformation Transformation  Model*   Transformation (generation through grammar) 3 [Tisi09] Tisi, M.; Jouault, F.; Fraternali, P.; Ceri, S. & Bézivin, J. On the Use of Higher-Order Model Transformations. ECMDA-FA, LNCS: 5562, pp. 18-33, Springer-Verlag. Enschede (The Netherlands), June 2009

4. Higher-Order Transformation Classification A HOT is just a transformation: The same classification as for simple model transformations can be applied Keeping in mind that the input and/or output models are transformations themselves. 4

5. Higher-Order Transformation 2 Uses of HOT (inspiration from [Tisi09]) Transformation Synthesis Input:  or Model – Output: Transformation Mapping Implementation  Reduce abstraction level: QVT-Relations  QVT-Core (w.r.t. traces) [OMG08]  Declarative to Operational specification: TGG rules  TGG operational rules [Klar07] 5 TGG rule TGG operational rules [OMG08] OMG. Meta Object Facility 2.0 Query/View/Transformation Specification. April 2008. [Klar07] Klar, F.; Königs, A. & Schürr, A. Model transformation in the large. ESEC/FSE, pp. 285-294, ACM. Dubrovnik (Croatia), 2007.

6. Higher-Order Transformation Uses of HOT Transformation Synthesis Input:  or Model – Output: Transformation Generic Transformation Input or output meta-models of a transformation is not known a priori: generate a transformation on-the-fly specific to the input or output meta-models.  HOT takes as input a meta-model MM and outputs a transformation model T. T takes as input two models that conform to MM and outputs the difference model between them: union of both models + annotations (similar, from left, from right) [Graaf07] 6 [Graaf07] Graaf, B. & van Deursen, A. Using MDE for generic comparison of views. Models in Software Engineering, INRIA. Nashville (USA), October 2007.

7. Higher-Order Transformation Uses of HOT Transformation Analysis Input: Transformation – Output: Model* Generate data information from a transformation for analysis purposes Query a transformation model  Transform the operational semantics of a Petri-Net-like language defined as a graph transformation, together with an instance model of the language into a Petri-Net. [Lara10] This Petri-Net can be used for analysis. 7 [Lara10] de Lara, J. & Vangheluwe, H. Automating the transformation-based analysis of visual languages. Formal Aspects of Computing, 22, no. 3-4, pp. 297-326, Springer. May 2010.

8. Higher-Order Transformation Uses of HOT Transformation Composition / Decomposition Input: [1..*] Transformation – Output: [1..*] Transformation Compose two transformations into one: complex merge of the rules Weaving of transformations: chain transformations with separate concerns (e.g. multi-stage)  See “Application” part of this lecture: adding animation concern to a Petri-Net simulator 8

9. Higher-Order Transformation Uses of HOT Transformation Migration Input: Model – Output: Transformation When a language evolves, all associated transformations must be adapted. 9

10. Higher-Order Transformation Uses of HOT Transformation Modification Input: Transformation – Output: Transformation (INPLACE) Modify the semantics of the transformation engine Add a copy operator rules Add a grouping mechanism in the patterns Transformation Optimization Improve the transformation definition for more efficient results Refactor a transformation with best practices 10 [0..1]

11. Higher-Order Transformation 3 Precise Modelling of Transformations “A higher-order transformation is a model transformation such that its input and/or output models are themselves transformation models.” model transformation The notion of model transformation  Manipulation of any model (see “Model Transformation” talk). transformation model The notion of transformation model  Transformations must be modelled and thus conform to a meta-model. Model everything explicitly... But in which formalism? Which meta-model? 11

12. Higher-Order Transformation Models, Meta-Models, and Transformations T: operation that transforms the model M 1 into M 2. M T : model of a transformation that transforms any model of MM 1 into a model of MM 2. MM T : meta-model of all transformations that transform any meta-model. MMM: meta-model of the language used to describe meta-models. 12 MM’ T MM 1 MM 2 MM T MMM MTMT conforms to is modelled by transformed to

13. Higher-Order Transformation What is the most appropriate formalism for MM T ? MM TU : meta-model of the transformation units (rules, primitive operators,...) MM SC : meta-model of the scheduling language MM PL : meta-model of the pattern language 13 MM’ T MM 1 MM 2 MM T MMM MTMT

14. Higher-Order Transformation Precise Modelling of Transformations MoTif transformation language [Syriani10] 14 [Syriani10] Syriani, E. & Vangheluwe, H. A Modular Timed Model Transformation Language. McGill University, no. SOCS-TR-2010.4, School of Computer Science. March 2010. MM SC MM TU

15. Higher-Order Transformation What about MM PL ? [Kuhne09] Unlike the transformation units and scheduling sub-languages, the pattern language depends on other languages: the domains of the transformation. 1.Generic pattern language +Most economic solution -Generic concrete syntax (MOF-like) -Allow to specify patterns that will never occur 2.Customized pattern language +Concrete syntax adapted to the source/target languages (DSL) +Exclude patterns that do not have a chance to match -More work for the tool builder 15 [Kuhne09] Kühne, T.; Mezei, G.; Syriani, E.; Vangheluwe, H. & Wimmer, M. Explicit Transformation Modeling. MODELS 2009 Workshops, LNCS: 6002, pp. 240-255, Springer. Denver (USA) 2010.

16. Higher-Order Transformation What about MM PL ? RAM process: (quasi-)Automatically generated environment for pattern language 16 Input Meta-ModelOutput Meta-Model Relax Augment Modify Customized Pattern Meta-Model

17. Higher-Order Transformation What about MM PL ? RAM process: generate pre-/post-condition patterns meta-models Relaxation: Concretize abstract entities Reduce minimal multiplicity constraint Constraints (automatic?) Free form: no constraints Valid elements: ensure typing Valid multiplicities: enforce (relaxed) multiplicities Valid constraints: enforce (a subset of) meta-model constraints 17

18. Higher-Order Transformation What about MM PL ? RAM process: generate pre-/post-condition patterns meta-models Augmentation: Type all meta-model entities to MT(pre/post)_Element Add model transformation specific properties Labels Parameter passing (pivots) Allow abstract rules* Other (e.g., isProcessed ) Generic elements Trace elements 18

19. Higher-Order Transformation What about MM PL ? RAM process: generate pre-/post-condition patterns meta-models Modification: Pre-condition pattern constraint Attributes are of type constraint Post-condition pattern action Attributes are of type action Concrete syntax Abstract classes Association ends Other (e.g., replace topological visual syntax constraints) 19

20. Higher-Order Transformation What about MM PL ? RAM process: Generate the MM PL for Finite State Automata 20 RelaxAugmentModify

21. Higher-Order Transformation Is RAM a HOT? Answer: It takes as input the meta-models of the source and target languages. It produces as output a meta-model of transformations models. So it doesn’t take as input nor generate a transformation. 21

22. Higher-Order Transformation 4 HOT in Action [Kuhne09] 22 Translate Simulate Animate [Kuhne09] Kühne, T.; Mezei, G.; Syriani, E.; Vangheluwe, H. & Wimmer, M. Explicit Transformation Modeling. MODELS 2009 Workshops, LNCS: 6002, pp. 240-255, Springer. Denver (USA) 2010.

23. Higher-Order Transformation Meta-Model Definitions The meta-models of the domain 23

24. Higher-Order Transformation Transformation Meta-Model The meta-model of the transformation language 24

25. Higher-Order Transformation Transformation Meta-Model RAM The meta-model of the pattern language for the transformation (result of RAM) 25

26. Higher-Order Transformation Translation 26 Translate Translate: Denotational Semantics of Finite State Automata

27. Higher-Order Transformation Simulation 27 Simulate Simulate: Operational Semantics of Petri-Net

28. Higher-Order Transformation HOT in Action Meta-Models must include animation support The user adds correspondence links. Therefore the meta-models have evolved. We want to evolve the transformations without affecting the existing transformations. Simulate  HOT: Transform the Simulate transformation to include animation support. 28

29. Higher-Order Transformation Expected outcome of HOT 29 The animation transformation

30. Higher-Order Transformation HOT in Action 30  At the rule level, when an PN element is created from an FSA element, add a correspondence link between them.

31. Higher-Order Transformation HOT in Action 31  At the scheduling level, add the animate rules at the last step of the simulator’s loop.

32. Higher-Order Transformation Higher than first-order transformation second order transformation  Can you think of a second order transformation? i.e., a transformation that takes as input and outputs a HOT. In model-based testing, a technique called mutation analysis proposes to test transformations on faulty models (mutants). It allows to assess how effective a transformation can detect faulty models. A mutation on a model can be easily defined by a transformation. first-order transformation The faults in the mutant models must be realistic. To ensure that, we can create a first-order transformation that takes as input a meta-model and outputs a transformation (mutation operator). The mutation operator takes as input a model and that generates realistic faulty models w.r.t the meta-model provided. But now we want a composite mutation operation that mutates models by combining primitive mutation operators: transforming mutation operators. This can be done with a second-order transformation. 32