You can do something like this in Cocoon: <map:transform type="cinclude"> <map:parameter name="parallel" value="true"/> </map:transform> Walter will recognize this since he and I were tossing this around in connection to federated searching (just ideas at this point, but a great acronym - SETH (Search Everything Till it Hurts!)). I seem to remember that you had to hack the cinclude transformer to get it to work with a dynamic source, but in 2.1, the docs suggest this is now built-in, see: http://cocoon.apache.org/2.1/userdocs/transformers/cinclude-transformer.html At its best, cocoon would give you parallel processing and caching. This would be a tough to build on its own. Those apache folks know their stuff. art