@Claus: As what I found, using XPath in a streaming mode is not possible out of the box in Java 5 or 6 (XPath 1.0 needs the DOM XML Document). JAXP 1.4 (part of Java 6) includes the StAX API and can be used in Java 5. But than we have to parse the XPath expression by our self and use the Iterator API (XMLEventReader)... I think this is not what we want... I will update the wiki page with the information, that the streaming() mode can not be used in conjunction with xpath().
@Charles: Thanks for the link. Do you plan to use a style sheet and split a big xml file into multilpe small files? Or is it possible with the pure Saxon Java API (without a style sheet) which returns an iterator? This could be also the solution for our requirements (pure Java API which we can use in a custom processor). Cheers, Christian