URI resolver: How often is it invoked?

Hi again,
I have made an extension of your default URI-resolver in order to device a scheme for making a caching one - maybe utiliizing a pre-loaded file-cache which has to be mapped to URI's of incoming requests..

I would like to make an URI resolver as independant of referenced included/imported XSDs as possible (the ones in the sky). When dealing with GML3, this can have tremendous performance benefits, as it consists of a very large set of schema-files.

I have watched how often URI-resolver is being invoked and it looks as it is being invoked several times for the same XSD-reference. Is URI-resolver invoked multiple times at the instant of a single schema reference or is it only invoked once for each schema-reference detected by XmlSchema during XmlSchema's unmarshalling/parsing of a single XSD?