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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: Wikipedia on XML
 Perhaps another thread would be: How would you like to see next generation XML described. For now the definition in Wikipedia has to flow from the W3C recommendations we have now. -----Original Message----- From: Amelia A Lewis [mailto:amyzing@talsever.com] Sent: Sunday, August 09, 2009 9:15 PM To: Michael Kay Cc: 'Jim Tivy'; Tim.Bray@Sun.COM; 'Dave Pawson'; 'Pete Cordell'; 'XML Developers List' Subject: RE: Wikipedia on XML On Mon, 10 Aug 2009 03:20:27 +0100, Michael Kay wrote: > There may be millions of markup languages that allow <a/> as a document, or > there may be none. It doesn't matter: <a/> is a well-formed XML document > regardless. I think this stuff about XML being used to define other markup > languages is a very confusing way of explaining things to newcomers. The > first thing to get across is that <a/> is (a document allowed by the rules > of) XML. Yes. It's probably not worthwhile to draw the distinction, in the article, between "well-formedness" and "validity", but it's probably important to have it in mind while writing the article. When people describe XML as a meta-language, or a syntax or language for defining markup languages, they are, in effect, talking about validity: documents are valid or invalid according to some schema (or similar mechanism). XML is still XML without a schema, and can be characterized without a schema (or DTD). XML has rules of well-formedness. It's true that these rules do not establish the tag names, but they do establish: that the XML declaration must be the first thing in the file (or stream) (FSVO "first", but it's a fairly rigorous V) that only whitespace, comments, and processing instructions may appear in the prologue (and epilogue? I don't think XML actually defines the epilogue, as MIME does) that there is a single root element for a document (but the restriction is relaxed for an XML entity) that every element must be closed (tags are paired or empty) that elements may not overlap that attribute content must be quoted with regard to namespaces, that every namespace prefix must be declared "before" use (FSVO "before") There are a fair number of XML dialects out there that are not easily represented in any common schema or specification (ant comes to mind, particularly, especially since it lends itself to extension). Even though you cannot validate these dialects, they are *clearly* XML. So ... I'd lean in the direction of *rejecting* the argument that XML is a complex beastie that provides tools for defining markup languages. That's certainly true, but it's equally true that there are markup languages that are clearly *XML* without much formal definition. In fact, there are probably quite a lot of "little" languages (for configuration and the like) that are almost entirely undocumented (and which default to "mustignore" semantics, for the most part). You can verify well-formedness without any knowledge of what's in the document, without knowing anything about any particular elements or attributes. You have named elements, named attributes; these have standard syntax. The XML spec doesn't specify what any of them are; it's extensible that way. You have comments and processing instructions; these have standard syntax. Again, there's no definition of what's *in* them; that's an extension point. It's an extensible markup language. Keep it simple. Amy! -- Amelia A. Lewis amyzing {at} talsever.com How do you make a cat go moo? Ask it: "Does a dog have the Buddha-nature?" _______________________________________________________________________ XML-DEV is a publicly archived, unmoderated list hosted by OASIS to support XML implementation and development. To minimize spam in the archives, you must subscribe before posting. [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ Or unsubscribe: xml-dev-unsubscribe@lists.xml.org subscribe: xml-dev-subscribe@lists.xml.org List archive: http://lists.xml.org/archives/xml-dev/ List Guidelines: http://www.oasis-open.org/maillists/guidelines.php 
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