From: "Murata Makoto" <>
To: <>
Sent: Sunday, April 29, 2001 9:58 PM
Subject: Issue: Should we disallow nested grammars?
> At present, nesting of grammars is freely allowed. I propose
> to disallow such nesting in V1.0.
I strongly disagree with this. I believe it to be a very good feature of
TREX that it allows all forms of pattern to be composed with very few
restrictions. A grammar is just another kind of pattern.
> First, I do not see any use cases. The TREX tutorial says:
> "Of course, in a trivial case like this, there is no advantage in nesting
> the grammars: we could simply have have included table.trex within the
outer
> grammar element."
>
> It further says: "However, when the included grammar has many definitions,
> nesting it avoids the possibility of name conflicts between the including
> grammar and the included grammar." In other words, we only have to
perform
> renaming upon inclusion. This is very easy.
Yes, it is easy for computers. But for humans, it means they have to create
a copy of a pattern and rename definitions. This renamed copy has to be
kept in sync with the original whenever it changes.
> Second, I believe that modularization mechanisms requires further study.
> I think that it is dangerous to provide nested grammars without fully
> understanding modularization.
Wherein lies the danger?
James
