Proposed text for Clause 9

[MURATA Makoto]

Dear colleagues,

Here is a proposed rewrite of Clause 9.  It is based
on Francis' wording but has been modified and further
expanded by two examples.  Thanks. > Francis.

Regards,
Makoto
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9. Extension elements defined by a markup specification (informative)

A markup specification that uses Markup Compatibility elements and
attributes to allow extensions in namespaces other than those defined by the
markup specification may also define one or more specific extension elements
in the namespaces that it defines. [Note: If the markup specification
includes a schema, any extension elements would normally be constrained by
the schema to occur only in specific markup contexts. end note].

If an MCE processor is configured to recognise extension elements, it
preserves them together with their attributes and contents.  See
Clause 9 for details.


[Example:

https://subversion.assembla.com/svn/IS29500/trunk/Part3/TestData/ExtensionElements/example1.xml

In this example, the e1:foo element contains the unknown:foo element.
Suppose that a markup configuration contains an expanded name
("http://www.example.com/e1", "foo") and that an application
configuration does not contain "http://www.example.com/unknown".
Then, the element e1:foo is an application-defined extension element.
Although the unknown:foo element does not belong to an understood or
ignorable namespace, the MCE processor preserves it and does not
report any errors. end example]

[Example:

https://subversion.assembla.com/svn/IS29500/trunk/Part3/TestData/ExtensionElements/example2.xml

In this example, Markup Compatibility elements and attributes occur
within the extensionElement element, which is the only child of the
root element example.  Suppose that a markup configuration contains an
expanded name ("http://www.example.com/e1", "extensionElement").
Then, the MCE processor preserves the extensionElement element.
Therefore, MCE elements and attributes within it, namely mce:Ignorable="i1",
mce:ProcessContent="i1:bar1", mce:MustUnderstand="e1",
mce:AlternateConent, mce:Choice, and mce:Fallback, appear in the output
document.  end example]

After receiving the output of an MCE processor, application programs
may further invoke an MCE processor to handle Markup Compatibility
elements and attributes within extension elements.