Namespaces and unique IDs

[Dizzy Haze]

This is probably a really dumb question, but I'm trying to get my head
around what's going on here.

I have this in my document:

<div xml:id="Area_0">
<svg xmlns="http://www.w3.org/2000/svg">
<rect svg:id="Area_0" x="49" y="116" width="64" height="64"/>
<rect svg:id="Area_1" x="250" y="272" width="128" height="130"/>
</svg>
</div>

This will not validate because there are two attribute of the type
xs:ID with the same value (Area_0) in the document.

Is this correct? I'm wondering if the different namespaces, xml:id and
svg:id, should cause the IDs to be considered independently of one
another. Or does an ID type apply everywhere, regardless of namespace?

Thanks.

 

[Martin Honnen]

Dizzy Haze wrote:

I have this in my document:

<div xml:id="Area_0">
<svg xmlns="http://www.w3.org/2000/svg">
<rect svg:id="Area_0" x="49" y="116" width="64" height="64"/>
<rect svg:id="Area_1" x="250" y="272" width="128" height="130"/>
</svg>
</div>

This will not validate because there are two attribute of the type
xs:ID with the same value (Area_0) in the document.

The prefix svg for those svg:id attributes is not even bound to a
namespace URI so I doubt you get to validation at all, that is not
well-formed.


And what schema do you try to validate against?

 

[Dizzy Haze]

The example is just a snippet. The actual document is well-formed.

Basically, what I'm wanting to know is if the xs:ID type applies across
all namespace IDs. That's it.

 

[Martin Honnen]

Dizzy Haze wrote:

Basically, what I'm wanting to know is if the xs:ID type applies across
all namespace IDs.

xs:ID is the same as the ID type in DTDs, it applies for the whole
document so within an document any ID value needs to be unique:
<http://www.w3.org/TR/xmlschema-0/#schemaConstraintsVsXML1>
If you want to have some restricted scope for a uniqueness constraint
then use the xsd:unique construct:
<http://www.w3.org/TR/xmlschema-0/#specifyingUniqueness>

 

[Dizzy Haze]

xs:ID is the same as the ID type in DTDs, it applies for the whole
document so within an document any ID value needs to be unique:
<http://www.w3.org/TR/xmlschema-0/#schemaConstraintsVsXML1>
If you want to have some restricted scope for a uniqueness constraint
then use the xsd:unique construct:
<http://www.w3.org/TR/xmlschema-0/#specifyingUniqueness>

Thanks Martin.

 

[Harrie]

Martin Honnen said the following on 2005-09-27 20:44 +0200:

The prefix svg for those svg:id attributes is not even bound to a
namespace URI so I doubt you get to validation at all, that is not
well-formed.

Can you elaborate? It looks well formed to me. What am I missing? I agree that svg:id is not bound to a namespace, but that's an attribute (of the rect element) and I thought well formedness has to do with elements.

Would it validate if "svg:id" was replaced by simply "id" since the default namespace (taken there is one somewhere in the document) is overriden by the namespace in the svg element?

 

[Henry S. Thompson]

xml:id [1], which is new, identifies its value as an ID. A conformant
processor adds that to the things known to be IDs as a result of
whatever other schema language it supports, e.g. DTD or W3C XML
Schema, to detect conflicts. Assuming your document has a declaration
which in some way makes svg:id of type ID, then yes, that document is
not valid per xml:id.

ht

[1] http://www.w3.org/TR/xml-id/
--
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
Half-time member of W3C Team
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