[xml] XML Schema Validation

[Kent Wilson <kenton wilson gmail com>]

Hello,

I have a question regarding the validation of XML schemas using libxml2. 
It is my understanding (In looking at the mail archive and the available doc-
umentation) that:

1.  libxml2 provides no support for at all for validation (DTD or Relax-NG) 
     of XML schemas if you are using the SAX model and APIs.

2. libxml2 provides support for validation of DTDs if you are using a DOM
    model and APIs.

3. libxml2 provides an "new" XmlTextReader interface which offers an altern-
    ative to SAX for "stream" processing of XML and also provides full DTD
    validation and partial or limited Relax-NG validation of the XML schema.

Is my understanding correct? 

Concerning the XmlTextReader interface and validation:

1. What are the limitations or restrictions on performing Relax-NG validation.
     I  don't understand what the "...only subsets which cannot be..." comment
     means (see http://xmlsoft.org/xmlreader.html#Validating).

2. If using the XmlTextReader interface for validation how much of the
    XML schema has to be kept in memory to perform the validation? My
    only concerng is that I don't defeat my original motiviation for using
    a "streaming" approach (i.e. a XmlTextReader (SAX-like)) to begin with.

Kent

kenton wilson gmail com