Towards Modular Code Generators
Using Symmetric
Language-Aware Aspects
Steffen Zschaler, Awais Rashid
FREECO’11
Lancaster, 26 July 2011

Motivation
Code generators can become quite complex
– Generate code related to a number of different
concerns / features
• Different model elements (global-to-local
transformation)
• Additional technical concerns (e.g., persistence
annotations)
– Flexibly combine generation pipeline depending
on features required
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Configuring Code Generators
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Application Model
Java Code
Business
Logic Generator
Java Data Model
Generator

Configuring Code Generators
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Application Model
Java Code
Business
Logic Generator
EMF GeneratorGUI Generator
plugin.xml

Existing Modularity Techniques
• Templates
– Typically one template per target file
– May produce more than one file
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Existing Modularity Techniques
• Templates
– Typically one template per target file
– May produce more than one file
• Generation Rules
– Allow hierarchy similar to operations
– Good for capturing common design rules
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Existing Modularity Techniques
• Templates
– Typically one template per target file
– May produce more than one file
• Generation Rules
– Allow hierarchy similar to operations
– Good for capturing common design rules
• Import of module templates
– Allow reuse of rules
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Existing Modularity Techniques
• Templates
– Typically one template per target file
– May produce more than one file
• Generation Rules
– Allow hierarchy similar to operations
– Good for capturing common design rules
• Import of module templates
– Allow reuse of rules
• Asymmetric Aspects
– Explicitly address tangling
– BUT...
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Drawbacks of Asymmetric AO
• Need for a base template
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Drawbacks of Asymmetric AO
• Need for a base template
• Need for scaffolding
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Drawbacks of Asymmetric AO
• Need for a base template
• Need for scaffolding
• No explicit support for weaving context
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Drawbacks of Asymmetric AO
• Need for a base template
• Need for scaffolding
• No explicit support for weaving context
• Not language aware
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Registration + Weaving =
Symmetric AO for Code Generation
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CG Template 1
CG Template 2
CG Template n
...

Registration + Weaving =
Symmetric AO for Code Generation
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CG Template 1
CG Template 2
CG Template n
Code
Slice
Registry
...

Registration + Weaving =
Symmetric AO for Code Generation
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CG Template 1
CG Template 2
CG Template n
Code
Slice
Registry
Code Slice Weaver
...

Registration + Weaving =
Symmetric AO for Code Generation
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CG Template 1
CG Template 2
CG Template n
Code
Slice
Registry
Code Slice Weaver Output
Files
...

Registration + Weaving =
Symmetric AO for Code Generation
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CG Template 1
CG Template 2
CG Template n
Code
Slice
Registry
Code Slice Weaver Output
Files
...

Registration + Weaving =
Symmetric AO for Code Generation
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CG Template 1
CG Template 2
CG Template n
Code
Slice
Registry
Code Slice Weaver Output
Files
...

Text Merging
• 2-way vs 3-way
– We can only support 2-way merging
• State-based vs change-based
– We can only support state-based merging
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based on Tom Mens’ classification

Text Merging
• 2-way vs 3-way
– We can only support 2-way merging
• State-based vs change-based
– We can only support state-based merging
• Textual vs syntactic vs semantic
– The more semantic the more powerful
– But also the more configuration needed!
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based on Tom Mens’ classification

Prototype
• Extends Epsilon Generation Language (EGL)
– New workflow tasks:
eglRegister – generate from a template, but store result in
registry
eglMerge – merge registry contents for specific files
– Can be configured with different text merging
algorithms
• Distribution uses FeatureHouse
• Available from EpsilonLabs:
http://epsilonlabs.googlecode.com/
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Conclusions & Outlook
• Asymmetric aspects can address some
modularity issues in code generation
• Presented a prototype
• Larger comparative study of modularity
properties currently under way
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THANK YOU FOR YOUR
ATTENTION!
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