Hi, David,
You are proposing that an application dissables the use of
schemaLocation/ noNamespaceSchemaLocation attributes and instead uses
user specified schemas.
I am not sure if it is a *perfect* solution. I would think that if a
namespace resolution using user specified schemas fails, you might want
to look at schemaLocation/ noNamespaceSchemaLocation attributes and try
to resolve namespace URI from the schemas specified on those attributes.
Can you explain, why you would want to ignore completely schemaLocation/
noNamespaceSchemaLocation attributes?
Thanks,
Elena
> "David E. Cleary" <[EMAIL PROTECTED]> on 06/04/2001 03:55:02 PM
>
> Please respond to [EMAIL PROTECTED]
>
> To: "Xerces-C-Dev" <[EMAIL PROTECTED]>
> cc:
> Subject: XML Schema Resolver proposal
>
> Currently it is a requirement to use xsi:schemaLocation and
> xsi:noNamespaceSchemaLocation in your XML instance data in order to get
> Xerces to do schema validation. The XML Schema Recommendation explicitly
> states that the inclusion of these attributes are only hints and there is
> no
> mandate that these attributes must be used. This is due to the fact that
> there are many use cases where you do not want to trust the instance data
> to
> validate itself, which is effectively what you are doing. For instance, in
> server side applications it is reasonable that all valid XML instances your
> application processes will have a schema that is stored locally to the
> system which has been verified and is trusted.
>
> Therefore, I propose that a Schema Resolver be created that works much like
> an Entity Resolver works today. An application would first disable use of
> xsi:schemaLocation and xsi:noNamespaceSchemaLocation so that schemas will
> not be automatically retrieved if the instance contains these attributes.
> Next, the application instantiates and registers an object that implements
> the SchemaResolver interface. This interface has a single method with the
> following signature:
>
> InputSource* resolveSchema
> (
> const XMLCh* const namespaceURI
> , const XMLCh* const schemaLocation
> );
>
> namespaceURI is the URI for the namespace that was declared and
> schemaLocation is the URL, if any, that was provided by the
> xsi:schemaLocation attribute for that particular namespace, if present.
> Otherwise, it is null.
>
> As the parser processes the instance document, resolveSchema will be called
> for every namespace declaration declared in the instance, unless a schema
> for that namespace has already be resolved. The method returns either an
> InputSource for a schema that defines that namespace, or null.
>
> As an alternative, overloading EntityResolver for this purpose is also an
> option. Personally, I believe that a namespace URI maps to a Public
> Identifier, and schemaLocation maps to a System Identifier, but that view
> is
> not shared by all. In any case, Xerces can not rely solely on
> xsi:schemaLocation to find and resolve schemas for validating instances.
>
> David Cleary
> the Progress Company
>
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