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Re: [xml-dev] ASN.1 is an XML Schema Language (Fix those lists!) and Bin
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On Saturday, Nov 1, 2003, at 17:57 America/Detroit, Bob Wyman wrote:
A call for fairness and equal rights...
Now that X.694 has been approved, ASN.1 based systems can generate and consume just about any XML object that can be defined using XML Schema. Thus, there seems to be no reason why ASN.1 wouldn't be considered to be just as much an "XML Schema Language" as any of the other more well-known languages like XML Schema, Relax NG, Schematron, etc. Yet, of hundreds of sites and many books that include lists and/or discussions of languages for describing XML schemas, virtually none mention ASN.1... This doesn't make sense to me.
"Just about any XML object" may be the operative phrase here. Can ASN.1 systems handle mixed content and open content models, e.g. XHTML? I was under the impression that ASN.1 could model strongly typed, regularly structured XML but haven't heard anyone advocate it for more content-oriented, document-like uses. If it can, some advocacy, and especially demonstrations of what concrete advantages ASN.1 might offer in specific circumstances would help spread the word.
It seems to me that responsible writers would include references to ASN.1 as an XML schema language. If ASN.1 was limited in its ability to describe XML objects,
This gets into another point -- there is a widely-held belief by many (most?) XML developers/analysts that XML *is* a text markup format, so "XML objects" is an oxymoron. See http://lists.w3.org/Archives/Public/www-tag/2003Oct/0036.html for the most recent outbreak of the long running debate on this point . (Note that I personally am on the "you also need a data model" side, but that doesn't mean that I'm ready to accept ASN.1 as an "XML" technology!).
Given that ASN.1 is now capable of fully describing XML objects, it should be included in all lists of "XML schema languages." And, we should put to bed the now mute discussion of "Binary XML." XML should stay in the realm it started in -- a text-based language for tagged data exchange. The problem of binary exchange is handled well by others...
Now I'm confused: If ASN.1 is an "XML" technology, isn't it a "binary XML" system, that is, an alternative Infoset with a range of possible serialization formats?
I'm probably more sympathetic to alternative serializations of the XML Infoset than most people on this list, but I'm far from convinced that ASN.1 is a useful part of the XML suite of tools. One exception would be in very limited circumstances where there a tight coupling between components of an application, a strong use case for XML Infoset-tools such as SOAP, DOM and XSLT, but for some reason XML itself is too inefficient in the application context. I can imagine that occurring in certain Web services contexts (and Sun has proposed an ASN.1 approach tailored to just that situation, see http://developer.java.sun.com/developer/technicalArticles/WebServices/fastWS/ ) but that's a fairly specialized scenario.
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