Re: [xml] xmlSchemaSAXPlug and xsi:schemaLocation

[Graham Bennett <graham-libxml simulcra org>]

On Mon, Oct 10, 2005 at 10:30:06AM +0200, Kasimier Buchcik wrote:
> 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".

Thanks Kasimier, I'll try this.  Just to check, is the 'late binding'
problem an issue with libxml2 schema in general or just when using the
SAX plug interface?

Thanks,

Graham.

-- 
Graham Bennett