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- From: David Megginson <david@megginson.com>
- To: "xml-dev" <xml-dev@ic.ac.uk>
- Date: 08 Jan 2000 09:37:23 -0500
"Frank Boumphrey" <bckman@ix.netcom.com> writes:
> > james anderson <James.Anderson@mecomnet.de> writes:
> >
> > > > ... it is possible to have a document that is well-formed but
> > > > not valid XML 1.0, but still conforms to Namespaces, RDF, or XLink
> > > > (though not XHTML, which requires validity for strict conformance).
>
> Well XHTML is no different from any other _document type_. A document type
> such as docbook or XHTML must conform to a DTD or it would not be a document
> type!
Wrong. A document type needs to conform to the specification that
defines it: the specification may or may not include a DTD, and may or
may not require the DTD to be used, but the DTD is at best an optional
(if extremely useful) part of a document type specification.
Here's an example of a document type whose specification does not
include a DTD:
Memo Document Type
------------------
Every memo document consists of a root element named "memo"
with two element children: "number" and "body", optionally separated
by whitespace. The contents of the "number" element shall be a
number between 1 and 99,999, assigned sequentially; the contents of
the "body" element shall be text containing a minimum of one and a
maximum of three sentences, using UK orthography.
Here's a document conforming to that document type:
<?xml version="1.0"?>
<memo>
<number>2,126</number>
<body>Look, mum, no DTD!</body>
</memo>
Now, I could have written a DTD and required its use as *part* of the
document type specification:
<!ELEMENT memo (number, body)>
<!ELEMENT number (#PCDATA)>
<!ELEMENT body (#PCDATA)>
However, it would be trivially easy to write documents that conform to
the DTD but not to the document type:
<?xml version="1.0"?>
<!DOCTYPE memo SYSTEM "memo.dtd">
<memo>
<number>Let me not to the marriage of true minds</number>
<body>123</body>
</memo>
All the best,
David
--
David Megginson david@megginson.com
http://www.megginson.com/
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