February 22, 2008

Bidirectional synchronization

The effort of blogging already seems to pay off as I start to get mails with interesting references to related work. Yesterday Miguel Garcia pointed me to his workshop paper Bidirectional Synchronization of Multiple Views of Software Models.

What I liked about the paper is its discussion of related work and the references that give a very comprehensive overview of the state of the art in this field, i.e., Miguel discusses with a bird's eye view approaches to solve the view update problem like program inversion, lenses, QVT, ATL and TGG (triple graph grammars, to be discussed in the future). Indeed, in my research on diagram editors I currently have to deal with the problem of reflecting changes on the abstract syntax level back to concrete syntax (and vice versa, of course).

Abstract of Miguel's paper:
Current best-practices for defining Domain-Specific Modeling Languages call for metamodeling techniques, which do not take into account the future use of such languages in multiview design environments. Tool implementers have tried a variety of ad-hoc techniques to maintain views in-synch, with modest results. To improve this state of affairs, a declarative approach is elaborated to automate multiview synchronization, building upon existing metamodeling techniques and recent advances in the field of function inversion for bidirectionalization. An application of these ideas to EMOF and a discussion of the resulting Declarative MVC software architecture are also provided. A significant benefit of the approach is the resulting comprehensive solution to a recurrent problem in the software modeling field.

I look forward to further external contributions!

February 21, 2008

Practical - end of first stage

The first stage of our practical on graph and model transformation is already finished. The students have produced nice class diagram editors with all three meta-CASE-tools. As expected, all tools have particular strengths and weaknesses.


  • Strong points: open source, integration with popular eclipse platform and EMF, wizards, tutorials

  • Weak points: difficult to realize nested packages, internal metamodels not documented very well (students sometimes had to consult the generated code to understand the differences of particular options), graphics cannot be defined in a visual way

DSL Tools:

  • Strong points: predefined skeletons, good documentation (in particular the book "Domain-Specific Development with Visual Studio DSL Tools"), good error messages, visual mapping between abstract and concrete syntax

  • Weak points: generated editors need Visual Studio, arrangement of the metamodel as a tree is rather confusing, nested packages difficult to realize


  • Strong points: good documentation, many examples, changes to graphics and metamodel on the fly, integrated code generator, nested packages possible

  • Weak points: generated editors need MetaEdit+, project portability, too many open dialogs in particular situations

The students have learned that domain specific languages can be realized with modern tools very conveniently.

February 12, 2008


Let me today write about a tool I have tried recently: VlDesk.

Compared to other research tools VlDesk outstands with a comprehensive website (including demos) and smooth installation procedure. The underlying formalism, eXtended Positional Grammars (XPG), is well-studied (see further reading) and allows for efficient parsing. In fact, the parser is generated using the well-known Yacc parser generator. All parts of this meta-CASE-tool are well-integrated. For instance, there is a graphical symbol editor and productions can also be defined in a visual way. One can easily switch between the perspectives for language design (Visual Grammar Environment) and usage (Visual Programming Environment).

However, there are also some weak points. For instance, the system is only available for Windows systems. Further, some examples and particular features have not worked properly.

All in all, VlDesk is a system worth to try out, in particular after reading the papers listed below.

Further reading:

  • Building syntax-aware editors for visual languages, Costagliola, G., Deufemia, V., Polese, G., Risi, M., 2005, Journal of Visual Languages & Computing

  • Extended Positional Grammars, Costagliola, G., Polese, G., 2000, Proceedings of the 2000 IEEE International Symposium on Visual Languages