Graph Transformation Day Bremen

Directly after the World Usability Day in Dresden I attended the Graph Transformation Day in Bremen. Here, I gave a talk about the generation of correctness-preserving editing operations for diagram editors. More on this later...

The other talks have been given by my supervisor Prof. Mark Minas (about using triple graph grammars for analysis in diagram editors), Dr. Rubino Geiß, the architect of the GrGen graph transformation engine (and indeed his talk was about the implementation and application of GrGen), and finally Edgar Jakumeit, who described the realization of recursive matching rules for GrGen. I have found these recursive "star" rules particularly interesting, because they actually allow to write parsers with GrGen in a declarative style. In a sense, this is quite similar to my approach to graph parsing via combinators.

It was a nice workshop. I learned a lot about the GrGen system. In particular I now have an idea how they managed to build the fastest (at least in quite some cases) graph transformation tool in the wild. Thank you Berthold for organizing this...

Roughly sketch your diagrams

In recent posts I have already demonstrated the power of diagram completion.

In the paper I have presented at this year's LED workshop, I have shown how diagram completion can be used in order to facilitate a completely novel(?) approach to diagram editing. It is enough to just roughly sketch your diagram. You do not need to hit the mark quite precisely anymore as required in traditional diagram editors. Rather the completion engine computes all ways, how the diagram can be put together. Thereafter, the completion causing minimal change to the layout of existing diagram components is selected automatically! I am quite sure that this feature can boost the accessibility of diagram editors.

Example:

This figure shows how tedious the manual correction of a roughly sketched diagram can be. At least three complex mouse dragging operations are necessary here. The completion engine would yield two results for this example, the diagrams A and B given in the upper row. However, it is quite clear which diagram the editor user would prefer: the one with minimal changes to his components, namely A. A shortcut that automatically applies completion A could greatly improve editing performance.

However: This approach is only possible as long as there are not too many possible compositions of the fragements. For instance, n disconnected NSD statements can be put together in n! ways. As a consequence, the user would have to invoke the completion engine every few steps. Even so, this kind of assistance is still useful.

• S. Mazanek, S. Maier, M. Minas. Exploiting the Layout Engine to Assess Diagram Completions. Proc. of the 2nd International Workshop on Layout of (Software) Engineering Diagrams (LED 2008), 2008. Electronic Communications of the EASST.

RTA 2008

I am just back from the RTA 2008 (Rewriting Techniques and Applications) conference in Linz. My talk has been on Wednesday and was about Functional-logic Graph Parser Combinators. I already have written on this blog about graph parser combinators, but this purely functional approach had several problems we solved using functional-logic programming techniques. In particular, the new framework can be used as a back-end for my approach to diagram completion.

Hagenberg, the conference location, is a nice little village 20km away from Linz. It has a romantic, medieval castle in which the conference took place. Furthermore, an important branch of the FH Oberösterreich is located here.

From the talks I attended I especially liked the invited one by Thomas Hillenbrand about the theorem prover Waldmeister which is known to be very fast and powerful. Recently, the popular computer algebra system Mathematica even incorporated the Waldmeister approach to equational theorem proving into its tool suite.

Although I do not know much about automatic theorem proving there have been some impressive facts I remember from the talk. First of all, it is still very important to think about the most efficient data structures for a particular application. In theorem proving execution time and memory usage are really a big issue, so every little improvement of the data structures might make a decisive difference. And second, there is no all-in-one algorithm suitable for every application domain. Thus, it is important to provide a flexible framework that can be parameterized by the users. In Waldmeister one has to choose among several weighting functions from which each one is superior for some special domains. Finally, automatic theorem proving has advanced a lot in the last years. Even for some "real proofs" there is a good chance that they can be found without much manual investigation.

GT-VMT, MetaEdit+

I am back from Budapest where I have attended the GTVMT workshop and ETAPS. The feedback to my talk about graph parser combinators was positive and I even have been pointed to very useful and interesting references later. I will provide a more detailed post about my stay in Budapest soon.

Let me just point you to an up to date news from the DSL tool market. I have already written about the MetaEdit+ tool. You might be interested in the news that this week MetaCase rolled out a new version of their tool as announced by the company's sales manager James Hammond. I have not tried the new version yet, so if somebody has tried it already: please leave a comment on your impression.

By the way, the CEO of MetaCase, Dr. Tolvanen, gave an interesting talk (slides) about the state of the art in the domain of DSL tools and the great speed ups that are possible with proper tool support. A main practical issue I have not been aware of before was the problem of a changing metamodel. According to Tolvanen MetaEdit+ is quite good at dealing with this issue due to its repository approach. I wonder how other tools deal with this issue. Any comments on this?

Visual Week and VL/HCC 2008

From September 15th, 2008 on the Visual Week will take place in Germany near Munich. Our department is organizing this event headed by Prof. Dr.-Ing. Mark Minas. One of the main conferences is the VL/HCC 2008, the 2008 IEEE Symposium on Visual Languages and Human-Centric Computing. Paper submissions here are due to March 11th, i.e., next Tuesday.

I hope to see you in Herrsching.

VL Conferences

You may be interested in using my public google calendar for conferences about visual languages:


I will assume no liability for the correctness of all dates. Its just a service. If you think an important date is missing or wrong please drop me a note.