View Source: WellFormed - Waikato Linux Users Group

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An [XML] document is [WellFormed] if it parses correctly. This means mainly that all tags must be closed, that they must be nested correctly, and that all attribute values must be quoted. This is not valid:

 <p>A paragraph <em><strong>here</em></strong>.
 <p>And another one there.

The paragraph tags are not closed, and the nesting for the emphasis and strong tags is wrong. To be WellFormed, this piece of the document has to be written like so:

 <p>A paragraph <strong><em>here</em></strong>.</p>
 <p>And another one there.</p>

In the second fragment, neither the <b> nor the <c> tag are closed. Unlike [SGML], [XML] does not allow tags to be automatically closed when the enclosing tag is closed. This is the reason why the <p> tag in [HTML]/[XHTML] gives people grief---in [HTML] you only need to put in the opened tags while in [XHTML] you need to put in both the opening and the closing tag.

If you want non-nesting overlapping ranges you cannot use something like

 <a> ... <b> ... </a> ... </b>

but should use something like

 <a id="1"/> ... <b id="2"/> ... <a id="1"/> ... <b id="2"/>

instead, and then you can reconstruct either of the tags as necessary.

;: ''I disagree strongly with that practice. You are undercutting the purpose of [XML] by flattening the markup. Instead, you should use attributes to your advantage.''

     <foo type="a" partof="1"> ... </foo> <foo type="a" partof="1" partof="2"> ... </foo> <foo type="b" partof="1"> ... </foo>

;: ''Yes, it's bulkier. Try in some way to process markup written with both approaches using [XSLT] and you'll notice the difference. %%% --AristotlePagaltzis''


[WellFormed] [XML] differs from [Valid] [XML] in that [Valid] [XML] has been (or could be) checked against a [Schema] or [DTD].

3 pages link to WellFormed:

Version 2, saved on Thursday, August 21, 2003 1:17:37 pm by AristotlePagaltzis

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