Differences between version 2 and predecessor to the previous major change of WellFormed.
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| Newer page: | version 2 | Last edited on Thursday, August 21, 2003 1:17:37 pm | by AristotlePagaltzis | Revert |
| Older page: | version 1 | Last edited on Thursday, August 21, 2003 12:09:47 pm | by StuartYeates | Revert |
@@ -1,31 +1,30 @@
-An [XML] document is [WellFormed] if it parses correctly. The main issue
that causes [XML] not to
be [WellFormed] is tag ordering
. For example the following
is [WellFormed]
:
+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
:
- ...
-
<a
>
- this is well formed
</b
>
-
<c
> this is well formed too
</c
>
-
</a
>
- ..
.
+ <p
>A paragraph
<em
><strong
>here
</em
></strong
>.
+ <p>And another one there
.
-while this is
not:
+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
:
- ...
-
<a
>
- this is well formed
<b
>
-
<c
> this is well formed too
-
</a
>
- ...
+ <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.
-The tag pattern:
+If you want non-nesting overlapping ranges you cannot use something like
<a> ... <b> ... </a> ... </b>
-is not WellFormed in either [SGML] or [XML], if you want non-nesting overlapping ranges such as this you need
something like:
+but should use
something like
<a id="1"/> ... <b id="2"/> ... <a id="1"/> ... <b id="2"/>
-then you can reconstruct either of the tags as necessary.
+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].
