1. Implementing Language Extensions with Model Transformations
Ivan Kurtev
Software Engineering Group
University of Twente
the Netherlands

2. Outline The Role of Languages in MDE; Language Elements;
Language Extensions;
Examples:
Language composition;
Abstract syntax extension;
Conclusions;

3. Use of Languages in MDE Languages for expressing models:
Meta-modeling: modeling of languages;
Transformation languages:
Can we use MDE techniques to solve language design problems?

4. Language Elements Concrete Syntax Abstract Syntax (L) Semantics:
Related to parsing;
Textual, visual;
Abstract Syntax (L)
Defines the structures represented by the concrete syntax;
Semantics:
Semantic Domain (D);
Semantic Mapping (M)
M: L -> D

5. Language Extensions Syntax Extensions: Semantic Extensions:
Extensible grammars;
Extensible parsers;
Macro definitions;
Semantic Extensions:
Modular attribute grammars;
Monads;
Action semantics;
Language Composition:
Involves syntax and semantic extensions;

6. Language Elements in MDA Terms (1)
Concrete Syntax: ?
Abstract Syntax (L)
Defined as a meta-model;
Semantics:
Semantic Domain (D): a model
Semantic Mapping (M): a model transformation;
M: L -> D

7. Language Elements in MDA Terms (2)
How can MDA techniques be used for language design tasks?
What do we gain (do we do better than the current techniques) ?
How are traditional problems solved in MDA?
Language reuse;
Language composition;
Language extension;

8. Example 1: Composing XML Languages
Application-specific XML processing:
XML Document
DOM
Parser
Processing
Code
DOM Tree
Application Objects
Transformation
Transformation from XML document to application objects;
XML Language Composition:
Concrete syntax composition is solved;
Semantic mapping: composition of transformations;
Semantic domain: software composition;
Application: hybrid XML languages and compound documents;

9. Transformation Pattern for XML Processing
Schema-less processing: based on DOM;
Schema-based processing: an XML schema and DOM are available;

10. Structure of XML Applications
Separation of concerns:
Syntax (schema);
Processing logic (transformation specification);
Application classes (semantic domain);

11. Example (1) Processing of a subset of SMIL timing module;
Source schema:
<attribute name=’begin’ type=’string’/>
<attribute name=’end’ type=’string’/>
<attribute name=’dur’ type=’string’/>
<attribute name=’timeContainer’ type=’string’/>
Example of a timed document:
<a timeContainer=’seq’ begin=’1’ dur=’20’>
<b timeContainer=’par’ dur=’10’>
<c timeContainer=’none’ dur=’10’/>
<d timeContainer=’none’ dur=’10’/>
</b>
<e timeContainer=’none’ dur=’10’/>
</a>
SMIL – Synchronized Multimedia Integration Language

12. Example (2)
Target Application Classes:

13. Composition of XML Languages
A new language may be composed with the timing module:
New processor is obtained via:
Composing target application classes (software composition);
Composing transformation definitions (based on the transformation language constructs);

14. Example 2: Abstract Syntax Extensions
Problem:
what if a transformation language does not support required compositional operators?
Possible Solutions:
Compose transformation definitions by applying a transformation;
Extend the transformation language with new constructs;
Example:
Extending the abstract syntax of a language;

15. Example 2: Implementation
Extended syntax is transformed to the initial syntax:

16. Sequential Composition of Extensions

17. Conclusions Examples of applicability of MDA techniques:
Composition of XML languages;
Abstract syntax extension;
Open Questions:
Are model transformations suitable for defining semantic mappings?
For which type of languages?
Scalability in case of language composition?
Comparison to other techniques (attribute grammars, action semantics,…)