Thanks a bunch. This helps a lot. Plus it gives me some ideas for other things I need to do.

Hi, I have to validate an XML document where there is a parent element <Output>, which, if present must have one or both of the following child elements: <errors>, <mappings>. (max. 1 instance each, unordered). Any ideas on what as possible schema would look like, if it is possible at all? tia, bob