User defined serialization attributes

Any number of user-defined attributes may be defined on xsl:output. These attributes must have names in a non-null namespace, which must not be either the XSLT or the Saxon namespace. The value of the attribute is inserted into the Properties object made available to the Receiver handling the output; they will be ignored by the standard output methods, but can supply arbitrary information to a user-defined output method. The name of the property will be the expanded name of the attribute in JAXP format, for example "{http://my-namespace/uri}local-name", and the value will be the value as given in the stylesheet.