Xtext and Java VM configuration

By developing DSLs with Xtext one usually work with two Eclipse workbenches:

• one by design-time containing three projects: the grammar, the DSL-editor and the generator,
  
• and a second one started from the first where the three DSL-plugin are deployed.
  

In order to avoid PermGem space problem it is important to configure properly the VM where the second runtime-workbench is started. A good setting is:


-Xms256m -Xmx512m -XX:MaxPermSize=256m

If you are working on Max OS you will possibly get the following errors : "Cannot load 32-bit SWT libraries on 64-bit JVM". To fix the problem I use the following VM parameters:

-d32 -Dosgi.requiredJavaVersion=1.5 -XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts -XX:MaxPermSize=256m -Xms256m -Xmx512m -Xdock:icon=../Resources/Eclipse.icns -XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts

Graphical versus textual DSLs

We are presently developing for a customer a DSL that aims to map different data structures. Our solution is based an Xtext of oAW. As its name said, Xtext is a framework that enables the development of textual DSLs. Our customer was scarred when he understood that he will have to WRITE code with our DSL. He had in mind a more user friendly DSL, something more graphical.

But is a graphical DSL more user frienly? Here some advantages that textual representations have over graphical notations:

• while graphical notations are often useful to describe structural concepts (e.g. class diagrams), textual notations are often a better fit for describing behavior or algorithms (e.g. expressions)
  
• expert users often find them faster and easier to modify
• there is a rich set of existing tooling for dealing with text files (diff, merge, copy & paste, search & replace ...).
• by using any source control systems (CVS, SVN, ...) it is possible to manage different versions of the DSL.

The textual or graphical nature of a DSL represents only the concrete syntax of the language. The abstract syntax is anyway independant of this discussion. This means also that it should alway be possible to transform a textual representation in a graphical one and vice versa.