
This function combines a base URI and a relative URI and returns the referenced resource.

The supported protocol identifiers are http: file: and virt:.  The virt: allows
referencing data stored in local Virtuoso tables without passing through HTTP.   See
@Entity References in Stored XML@ for details.

The effective URI will be the reference if the URI of the reference is absolute.  Otherwise it will
be the base URI modified by the relative reference.

Authorization is derived from the SQL or DAV identification of the caller.  The DAV
identification is used if processing DAV content in response to a DAV request.  The SQL user
account is used otherwise.

xml_uri_get returns the text of the requested resource. If specific encodings
or special authentication schemes are desired one may use
http_get directly.
