RE: Serialization (sometimes) needs to include type information

First, you need to give us some more information about the in-scope
schema components and validation mode for your query.

Assuming that you imported the two elements below, have the document
typed with the information and have lax validation mode, then your
result would be an element result of type xdt:untyped since it could not
find a definition in the schema components for the result element. This
then also means that the C elements will be untyped and not preserve
their original type.

So your example does not convey the semantics that you assume it does
and does not require a type serialization.

Also note that XML is primarily late typed data: You have the
self-describing XML document and you associate type information after
creation of a document. Thus, mandating the serialization of type
information and thus making the document early typed seems contrary to
the general XML philosophy.

Best regards
Michael (speaking for myself)

> -----Original Message-----
> From: public-qt-comments-request@w3.org [mailto:public-qt-comments-
> request@w3.org] On Behalf Of Antoine Mensch
> Sent: Wednesday, February 11, 2004 12:23 AM
> To: public-qt-comments@w3.org
> Subject: Serialization (sometimes) needs to include type information
> 
> 
> Consider the following schema fragment:
> 
> <xs:element name="A">
> 	<xs:complexType>
> 		<xs:sequence>
> 			<xs:element name="C" type="myns:Type1"/>
> 		</xs:sequence>
> 	</xs:complexType>
> </xs:element>
> 
> <xs:element name="B">
> 	<xs:complexType>
> 		<xs:sequence>
> 			<xs:element name="C" type="myns:Type2"/>
> 		</xs:sequence>
> 	</xs:complexType>
> </xs:element>
> 
> Now if we consider a document (or any other data source) containing
both A
> and B elements, the following query
> 
> <result>
> { 	for $x in doc("myDocument")//C
> 	return $x
> }
> </result>
> 
> returns a result that cannot be strongly typed without losing type
> information by any valid schema, as the schema spec forbids elements
with
> the same name and a different type in the same content model.
> 
> It seems to me that the only way of retaining type information would
be to
> annotate produced C elements with xsi:type. This could be a
serialization
> parameter, similar to the cdata-section-elements. However, this would
> raise
> another issue, as anonymous type names would then be exposed, and
would
> thus
> require to be handled in a consistent way by different XQuery and XML
> Schema
> processors.
> 
> This issue is important, especially for tools that perform distributed
> XQuery processing, and that need to retain consistent type information
> when
> moving XML data from one processing node to another.
>

Received on Wednesday, 11 February 2004 03:27:38 UTC