Transformations and Abstractions

The GPCE 2010 program committee has selected 18 papers from the submitted research papers. The complete list is available in the GPCE 2010 proceedings entry of researchr. Feel free to extend the entries with abstracts, identification of authors, and links to pre-prints.

I finally got back into the photo processing game by mastering selection with Adobe Bridge; first make a selection of photos and then only process the ones with highest rank; separation of duties. I shot some photos at last week's TOOLS 2010 conference, mostly during the dinners, since I was busy at other times. I uploaded the selection to a flickr set; here is a selection from the selection:

Today I've been participating in the Transformation Tool Contest 2010, which is held as part of the TOOLS 2010 conference in Malaga. The plan for my participation was the use of researchr for use in the evaluation of the results of the contest. Then it turned out that the example problem for the live part of the contest was evaluation of lambda terms. An excellent problem to tackle with Spoofax. So after doing some last improvements of researchr, I spent the afternoon creating a little lambda language environment.

The source code of the project is part of the Spoofax contributions directory.

Here is the Eclipse editor:

In the figure example.lam is the input for the transformation in concrete syntax; example.aterm is the abstract syntax for example.lam; example.nf.aterm is the result of normalizing example.aterm; finally, example.nf.lam is the result of pretty-printing the normal form. The result should be the correct addition of the lambda numeral for 2 with itself.

The syntax of the language is defined in SDF:

The Lambda.sdf module contains the definition of the concrete syntax. The Lambda.str module is automatically derived from Lambda.sdf and defines the abstract syntax (as an algebraic signature in Stratego).

The transformation is defined in Stratego. Here are the rules for pretty-printing and beta reduction:

Renaming rules are used to introduce the bindings of bound variables. The check rule verifies that no two definitions for the same name are given. The warning rule finds free variables and gives a warning in the editor.

Here's a screencast with a little demo to give an impression of the environment:

download

In my keynote talk at the Model-Driven Service Engineering workshop in Malaga (co-located with ICMT and TOOLS) I gave a presentation of mobl, the domain-specific language for mobile (web) application development that we (Zef Hemel) are developing.

"In the beginning were the words, and the words were trees, and the trees were words. All words were made through grammars, and without grammars was not any word made that was made. Those were the days of the garden of Eden. And there where language engineers strolling through the garden. They made languages which were sets of words by making grammars full of beauty. And with these grammars, they turned words into trees and trees into words. And the trees were natural, and pure, and beautiful, as were the grammars.

Among them were software engineers who made software as the language engineers made languages. And they dwelt with them and they were one people. The language engineers were software engineers and the software engineers were language engineers. And the language engineers made language software. They made recognizers to know words, and generators to make words, and parsers to turn words into trees, and formatters to turn trees into words.

But the software they made was not as natural, and pure, and beautiful as the grammars they made. So they made software to make language software and began to make language software by making syntax definitions. And the syntax definitions were grammars and grammars were syntax definitions. With their software, they turned syntax definitions into language software. And the syntax definitions were language software and language software were syntax definitions. And the syntax definitions were natural, and pure, and beautiful, as were the grammars."

Thus starts our essay on declarative syntax definition, which has been accepted for presentation at the Onward! 2010 conference:

Lennart C. L. Kats, Eelco Visser, Guido Wachsmuth. Pure and Declarative Syntax Definition: Paradise Lost and Regained. In Proceedings of Onward! 2010. ACM, 2010. (draft of final version)

Abstract Syntax definitions are pervasive in modern software systems, and serve as the basis for language processing tools like parsers and compilers. Mainstream parser generators pose restrictions on syntax definitions that follow from their implementation algorithm. They hamper evolution, maintainability, and compositionality of syntax definitions. The pureness and declarativity of syntax definitions is lost. We analyze how these problems arise for different aspects of syntax definitions, discuss their consequences for language engineers, and show how the pure and declarative nature of syntax definitions can be regained.

The slides of my keynote talk at Code Generation 2010 with an appendix about model-to-model transformation and transformation strategies.

In the fifth lecture in the Model-Driven Software Development course at TU Delft I talked about strategies for design and implementation of domain-specific languages, illustrated with a sketch of the mapping from WebDSL to Java.