Eliminating Crosscutting Constraints from Visual Model Transformation

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Eliminating Crosscutting Constraints from
Visual Model Transformation
Budapest University of Technology and
Economics Department of Automation and Applied
Informatics Applied Computer Science Group

• László Lengyel, Tihamér Levendovszky
• and Hassan Charaf

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Outline

• Case Study
• Visual Modeling and Transformation System
• Crosscutting constraints
• Aspect-Oriented Constraints
• Global Constraint Weaver
• Summary

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Case Study

• The case study is a variation of the class model
  to RDBMS transformation (also referred to as
  object-relational mapping)

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Case Study Input and Output
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Graph Rewriting
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Model Transformation in VMTS

• Graph Rewriting (LHS ? RHS)
• Metamodel-Based Rewriting
• An instantiation of LHS must be found in the
  graph the rule being applied to instead of the
  isomorphic subgraph of the LHS
• Precondition and postcondition of the rewriting
  rules - OCL expressions in LHS and in RHS

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Metamodel-Based Rewriting

• An instantiation of LHS must be found in the
  graph the rule being applied to instead of the
  isomorphic subgraph of the LHS

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Visual Modeling and Transformation System (VMTS)
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The Transformation of the Case Study
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Crosscutting Constraints

• The constraint appears 30 times in 11
  transformation steps
• The constraint appears 16 times in 6
  transformation steps

-- Persistent class context Class inv
PersistentClass self.is_persistent 1
-- Nonpersistent class context Class inv
NonPersistentClass self.is_persistent 0
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Crosscutting Constraints 2

• Modification and deletion of the constraints is
  not consistent
• It is difficult to maintain and reason about the
  effects and purpose of constraints when they are
  scattered
• We need a mechanism to separate these concerns
• After we separated the constraints from the
  pattern rule nodes we need a weaver method

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Problem Statement

• Precondition and postcondition of the rewriting
  rules - OCL expressions in LHS and in RHS
• Case study
• Crosscutting constraints in metamodel-based
  rewriting rules
• Solution - aspect-oriented constraint management

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Remove Crosscutting Constraints
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Global Constraint Weaver
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Aspect-Oriented Constraints

• VMTS manages constraints using AO-techniques
• Benefits of the AO constraints
• It is beneficial to describe a common constraint
  in a modular manner and designate the places
  where it is to be applied.
• Consistent constraint modification
• The rewriting rules do not contain numerous
  constraints which make more tangled the already
  complex rewriting rules
• Reasoning about the whole transformation

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The correspondence between the AOP and AO
Constraint handling concepts
AOP AO Step Constraints
Join-point Pattern Rule Node (PRN)
Pointcut (name-based, property-based) Context of the OCL Constraint (type-based), Weaving Constraint (property-based)
Advice (before, after) Pre- and postconditions
Aspect AO Constraint
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Summary

• The metamodel-based specification of the
  rewriting rules allows assigning OCL constraints
  to pattern rule nodes
• We have introduced a mechanism how to separate
  crosscutting constraints
• Aspect-Oriented Constraints
• Type-based weaving with constraints
• GCW

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Questions

• ?