Edelta: an approach for defining and applying reusable metamodel refactorings

Dipartimento di Ingegneria e Scienze
Università degli Studi dell’Aquila
dell’Informazione e Matematica
Edelta: an approach for defining and applying
reusable metamodel refactorings
Lorenzo Bettini - DiSIA, University of Florence
Davide Di Ruscio – DISIM, Università degli Studi dell’Aquila
Ludovico Iovino – Gran Sasso Science Institute, L’Aquila
Alfonso Pierantonio - DISIM, Università degli Studi dell’Aquila

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ME+ CommitMDE Workshop at MODELS 2017 - September 18, 2017, Austin, Texas
Refactoring in metamodeling
- Metamodels play a key role in any model-based approach
- They are subject of evolutionary pressures that can arise for
several reasons and several maintenance goals
- Refactoring can be defined as the process of changing a
software system to improve its design, readability, and to
reduce bugs

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- Metamodel refactorings can be expressed as a sequence of
additions, deletions and changes of elements
- Metamodel refactorings can involve also complex operations,
which are obtained by mixing atomic changes
- Existing approaches are mainly based on tedious and error-
prone manual activities
- The possibility to organize and reuse already defined refactorings is
limited

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A simple metamodel evolution

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Evolution
The attributes firstname and lastname of the
metaclass Person have been merged into the
new name attribute

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EvolutionThe metaclass Place has been added
as an abstract super class of
WorkPlace and LivingPlace
Their address attribute has been
pulled-up in the new metaclass

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Evolution
The gender attribute of the metaclass Person has been
replaced by the new sub-classes Male and Female

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Evolution
The reference works of the metaclass Person has been
replaced by the new metaclass WorkingPosition between
the new version of Person and WorkPlace

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Modelers might want to define reusable metamodel changes so to
similarly evolve other metamodels in the future

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1. The attributes firstname and lastname of
the metaclass Person have been
merged into the new name attribute;
2. The metaclass Place has been added as
an abstract super class of WorkPlace
and LivingPlace. Their address attribute
has been pulled-up in the new
metaclass;
3. The gender attribute of the metaclass
Person has been replaced by the new
sub-classes Male and Female
4. The reference works of the metaclass
Person has been replaced by the new
metaclass WorkingPosition between the
new version of Person and WorkPlace
Extract Superclass
Introduce Subclass

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Mastering Metamodel Refactoring
- Operating metamodel refactorings without a dedicated support can be an
error-prone task
- There is the need for languages and tools supporting the specification
and application of metamodel refactorings in a disciplined way
- The used language should provide at least the following characteristics:
- Conciseness and comprehensibility
- Integration
- Static checks
- Refactoring composability
- IDE support

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The Edelta Language
- Edelta is a domain specific language for specifying and applying
metamodel refactorings
- It provides modelers with constructs for specifying atomic
refactoring:
- additions, deletions and changes
- and to define complex reusable metamodel changes by properly
composing already defined ones

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A simplified version of the Edelta metamodel

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Xtext-based implementation of Edelta

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Xtext-based implementation of Edelta

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Applying Edelta to PersonList metamodel
example Edelta program

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example

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example
Edelta libraries
Edelta program

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The Edelta editor
- The Edelta editor provides typical Eclipse tooling mechanisms

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The Eclipse-based Edelta editor
- The Edelta editor provides typical Eclipse tooling mechanisms
static type checking,
syntax highlighting,
code completion,
..

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The Eclipse-based Edelta editor
- On-the-fly
interpretation of the
specified
refactorings
- Immediate view of
the modified Ecore
model in the Outline
view.

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Application of a sample Edelta specification
Applied to
Result

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Discussion points
Edelta vs. traditional GPL techniques
- Conciseness and comprehensibility. If we compare the Edelta
specification of the running example with the generated Edelta Java
code in terms of lines of code, the result would be 42 vs 225 LOC
- Integration: We designed Edelta in order to enable its integration
with EMFMigrate. Edelta will be used to specify the patterns that
have to be matched to trigger model migrations
…

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Discussion points
…
- Static checks: Edelta is able to detect refactoring errors at
compilation time
- Refactoring Composability: possibility of defining reusable
refactoring libraries that can be included when specifying Edelta
programs
- IDE support: Edelta is distributed with a complete Eclipse IDE
tooling support available at https://github.com/LorenzoBettini/edelta

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Conclusions
- In Model Driven Engineering metamodels play a key role
- Similarly to any kind of software artifacts, metamodels can evolve
- Edelta is a domain specific language for specifying and applying
reusable metamodel refactorings
- It allows the developer to specify both atomic and complex changes
- The implementation of Edelta is based on Xtext
- The language is endowed with an Eclipse-based development environment
providing also early evaluation of the refactoring being applied

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Future work
- Extend the language and supporting environment by introducing the
notion of quality models
- modelers will have the possibility to assess the refactoring impact on the
quality attributes that might be defined and associated to the metamodel
being changed
- Adoption of the language for specifying the evolution of other kinds
of modeling artifacts
- E.g., model transformations, models, …
- Use of the language in coupled evolution scenarios
- Integration in EMFMigrate

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Thank you !!!!

Edelta: an approach for defining and applying reusable metamodel refactorings

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