UMLX : A Graphical Transformation Language for MDA

1
UMLX A Graphical Transformation Language for MDA

• E.D.Willink, EdWillink_at_iee.org
• GMT Consortium, www.eclipse.org/gmt
• (Thales Research and Technology (UK) Limited,
  Reading, England)
• 2nd Generative Techniques in the Context of the
  Model Driven Architecture Workshop
• OOPSLA2003, Anaheim
• 26 October 2003

2
Overview

• UML and QVT perspective
• Use UMLX in less obvious ways
• workshop paper shows use as a programming
  language
• Not UMLX Concrete Graphical Syntax
• see the workshop paper
• Transformation as a Composable Component
• Summary

3
Transformation in Program Context

• Start state comprises the input model(s)
• End state comprises the output model(s)
• For QVT
• Transformation hierarchy is the full program
• More generally
• Transformation is a more powerful form of state
  transition

4
Transformation Syntaxes

• 1 Abstract Transformation Syntax (QVT)
• 1 Concrete Textual Syntax
• 1 Concrete Graphical Syntax
• Transformations
• to QVT (extract information content)
• between formats via XMI or XMID

5
MDA Models

• Platform Independent Model
• specification of what needs to be done
• too abstract for implementation
• Platform (Description) Model
• physical, virtual, intellectual
  resourcesavailable to implement solution
• Platform Specific Model
• a particular implementation
• Mark Model
• PIM PDM specific configuration

6
MDA Meta-Models

• Every Model is an instance of some Meta-Model
• traditionally the meta-model has been undefined
  but implicit
• with MDA we model it

7
Transform as a Model

• Transform may also be a model
• traditionally just Java code
• but even Java code is an instance of the Java
  meta-model
• Closed perspective - frozen executable
• Open perspective - generic engine, re-usable
  model

8
Transform between Meta-Models

• Every model instantiates a meta-model
• Transformation meta-model reuses input/output
  meta-model
• UMLX extends UML for transformations

9
Transformation

• From LHS
• read-only
• shared
• To RHS
• write-only
• shared
• non-conflicting
• In-place if LHS and RHS are same model instance
• Define LHS meta-model
• Define RHS meta-model
• Define transformations between meta-model
  instances
• (and pivot models if complex)

10
Match order

• Select search order - a1,a2, b1,b2,b3,
  c1,c2, d, e, f, g 'loop hoisting'

11
Schema driven matching

• Branch and bound search
• Advance one node/free variable per level
• pick narrowest relationship to advance to next
  node
• composition gt association
• forward gt backward
• unity multiplicity gt multiple
• validate advance
• type
• back relationships
• constraints
• nested transformations
• Smarter heuristics can lookahead

12
Composition

• Re-usable black boxes
• Encapsulation
• internal data
• internal behaviour
• Defined Interface
• external data
• external behaviour
• Meta-Models define what the external data
  comprises
• Ports define where the external data flows

13
Scheduling/Synchronisation

• Data flow defines when transformation occurs
• when the input models exist, then output gets
  created
• Evolution identities (and ordered sets) define
  how
• multiple concurrent match results are combined
• multiple concurrent transform results are
  combined
• Shared, read-only LHS
• Shared, non-conflicting write-only RHS
• Declarative, with causal constraints

14
Re-usability

• The UML to RDBMS example
• http//dev.eclipse.org/viewcvs/indextech.cgi/gmt-h
  ome/doc/umlx/M4M03.pdf?revHEAD
• 11 transforms in UMLX
• multiple transforms/steps/rules/helpers in other
  approaches
• UMLX transform unifies concepts
• Rule/Step is a transform with inputs/outputs
  bound
• steps may be factored out as (sub-)transformations
  
• Helper is a transform with inputs bound
• predicates may be factored out as
  (sub-)transformations
• Graphics scalability problems soluble
• factoring out sub-transformations with good clear
  names
• use of embedded OCL

15
UMLX Support

• UMLX editor configured within GME
• by defining a UMLX editing meta-model
• UMLX compiler designed in UMLX
• over 200 diagrams so far
• UMLX execution engine designed in UMLX
• over 100 diagrams so far
• Bootstrap by manual transliteration to NiceXSL
• human-friendly form of XSLT
• Prototype generates XSLT code
• currently for concurrent and sequential
  transforms on classes
• gt Fast, configurable, custom compiler-compiler

16
Summary

• UMLX is a natural extension of UML
• opportunities for more elaborate/useful syntaxes
• UMLX exhibits good composition properties
• declarative transform sequencing
• can degenerate to imperative
• declarative transform concurrency
• can be ordered
• arbitrary OCL at innermost level
• influence the QVT abstract syntax
• UMLX tools progressing