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Subject: Re: Issue: Should we disallow nested grammars?
From: "Murata Makoto" <mura034@attglobal.net> To: <trex@lists.oasis-open.org> 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
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