[antlr-interest] Thoughts on tree construction

[Oliver Zeigermann]

Tiller, Michael (M.M.) wrote:
One last comment thought on this idea.  As far as I can tell, there
> really isn't a formal mechanism for validating an AST in ANTLR or
> formally stating it.  The tree walker grammar formally describes this,
> but it isn't very useful outside of ANTLR.  I could imagine that if ASTs
> were based on XML, part of the compiler process could be to
> automatically formulate a DTD (or other type of schema) for the AST that
> would be generated.  If you work completely within ANTLR, this might not
> be useful, but if you were to interact with other tools, such a formal
> statement of the tree structure might be useful.

DTDs are only useful in the XML world, ANTLR tree grammars in the ANTLR 
world. Are you thinking of some sort of transformation from DTD to tree 
grammar? Or the other way round? What for? A DTD is only good for 
validation while tree grammars usually contain both analysis and 
synthesis. The synthesis part of XML usually is contained in informal 
code that works on the DOM, SAX, JDOM or whatever data structure. So 
tree grammars are much more poweful than a DTD or a Schema. Comparing 
ANTLR tree grammars to transformation languages like XSLT would make 
much more sense.

Oliver


 
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