Re: [xml] xmlSchemaSAXPlug and xsi:schemaLocation

[Kasimier Buchcik <K Buchcik 4commerce de>]

Hi,

On Sun, 2005-10-09 at 21:41 +0100, Graham Bennett wrote:
> Hi,
>
> I've been playing with xmlSchemaSAXPlug to do schema validation on my
> own stream of SAX events and it's proving to be very useful.  However it
> seems that a schema is required to be provided up front in order to get
> an xmlSchemaValidCtxt.
>
> Is there any automatic way to handle the situation where the schema
> location is provided as an xsi:schemaLocation attribute in the SAX
> stream, or should I just handle it myself?  I suppose I should be able
> to detect such an attribute, plug in the validating sax handler, then
> replay the events I have already seen, but this seems a bit messy.

Create the schema validation context with a NULL for the @schema
argument if you want to switch on xsi-driven schema acquisition.
Internally a new schema will be created during the validation and
all the schemata, specified via xsi, will be constructed.
However, this is a bit limited, since Libxml2's schema processors
wants references to schema components to be resolved after each
schema construction episode; thus it will work only on a subset
of all the possible scenarios. E.g. if you have a schema at the
document element, which references a component which would be
acquired deeper in the tree (via a second xsi acquisition) then
you would get a reference resolution error with Libxml2, while the
spec allows such "late binding".

Regards,

Kasimier