[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Is XML a Language? (was RE: XSLT Architecture: Nex
Hi Bill, Bill said: Obviously if we're talking about different concepts we're unlikely to come to agreement on a common "defintion". XML is most definitely a Context Free Language specified by a Context Free Grammar. It is also definitely NOT a natural language. Didier replies: Gee and I wanted to close this thread :-) ... Firstly, formal and non formal languages refer to a common base Noam Chomsky's work. Noam Chomsky is a linguist. Secondly, we are going beyond the focus of this list and I suggest that anyone wanting to continue this conversation can email me directly to martind@xxxxxxxxxxxxxx Thirdly, yes I know what a context free language (CFL) is and I don't confound natural and formal languages. I - in my original message - simplified the issue to make it easier to grasp for someone who asked a question and make an emphasis that XML, per se, is a tool used to create languages. Is a CFL a set of rules, somewhat but it's a high level abstraction, and the XML specifications go beyond that (for instance, definition of external entities - that call for an importation mechanism not part of a CFL or CFG definition). Is a DTD a CFG grammar? Yes it is. Do XML has several CFG properties? yes seen from a certain perspective. Can we say that XML + schema languages are a set of rules that anyone can use to create a language? yes. Can we say that a CFG language can do that? yes but with little extras to make it practical and fill the gap between the abstraction and the desired target language. Can we say XML is a strict CFL? No, the specs go beyond that. Can formal languages be reduced to CFL, yes and some notation languages exist for that and again, the XML recommendation goes beyond a strict CFL notation. However the DTD part of the recommendation is pretty close to a CFG definition since it leads to content models using production rules (a CFL characteristic). Conclusion: Can we say that XML as specified by W3C recommendation is CFG? I would prefer to cite Derick Wood on that: " The Standard Generalized Markup Language (SGML) is a meta-syntactic language for the definition of Document Type Definitions (DTDs), which are, essentially, extended context-free grammars in which the right-hand sides of productions are similar to regular expressions and are called content models. The Extensible Markup Language (XML) is, essentially, a simplified version of SGML used to specify DTDs of Web-based documents." I don't want to pollute this list with these issues, please email me personally if you want to continue this thread. Cheers Didier PH Martin XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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