Is mixed inherited when a complexType is extended? - xsd

Question

I have the following in a schema:
<xs:element name="td">
<xs:complexType>
<xs:complexContent>
<xs:extension base="cell.type"/>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:complexType name="cell.type" mixed="true">
<xs:sequence minOccurs="0" maxOccurs="unbounded">
<xs:element ref="p"/>
</xs:sequence>
</xs:complexType>
Some parsers allow PCDATA directly in the element, while others don't. There's something in the XSD recommendation (3.4.2) that says when a complex type has complex content, and neither has a mixed attribute, the effective mixed is false. That means the only way mixed content could be in effect is if the extension of cell.type causes the mixed="true" to be inherited.
Could someone more familiar with schemas comment on the correct interpretation?
(BTW: if I had control of the schema I would move the mixed="true" to the element definition, but that's not my call.)

Answer 1

Anyone reading my question might want to read this thread also (by Damien). It seems my answer isn't entirely right: parsers/validators don't handle mixed attribute declarations on base/derived elements the same way.
Concerning extended complex types, sub-section 1.4.3.2.2.1 of section 3.4.6 in part 1 of W3C's XML Schema specification says that
Both [derived and base] {content type}s must be mixed or both must be element-only.
So yes, it is inherited (or more like you cannot overwrite it—same thing in the end).
Basically, what you've described is the desired (and as far as I'm concerned) the most logical behavior.
I've created a simple schema to run a little test with Eclipse's XML tools.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="c">
<xs:complexType>
<xs:complexContent mixed="false">
<xs:extension base="a"/>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:complexType name="a" mixed="true">
<xs:sequence minOccurs="0" maxOccurs="unbounded">
<xs:element name="b"/>
</xs:sequence>
</xs:complexType>
</xs:schema>
The above schema is valid, in the sense that not Eclipse's nor W3C's "official" XML Schema validator notices any issues with it.
The following XML passes validation against the aforementioned schema.
<?xml version="1.0" encoding="UTF-8"?>
<c xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="test.xsd">
x
<b/>
y
</c>
So basically you cannot overwrite the mixedness of a complex base type. To support this statement further, try and swap the base and dervied types' mixedness. In that case the XML fails to validate, because the derived type won't be mixed as it (yet again) cannot overwrite the base's mixedness.
You've also said that
Some parsers allow PCDATA directly in the element, while others don't
It couldn't hurt to clarify which parsers are you talking about. A good parser shouldn't fail when it encounters mixed content. A validating parser, given the proper schema, will fail if it encounters mixed content when the schema does not allow it.