How in XML-schema do you make sure that of two possible child elements, either or both, but not neither are present? Parent A Parent B Parent A B should all be ok, but not Parent without either A or B. Attached is a small ZIP file with example files. Paris was a good meeting, I am working on the minutes! Thanks! Gregor ---------------------------------------------------------- Gregor Hagedorn (G.Hagedorn@bba.de) Institute for Plant Virology, Microbiology, and Biosafety Federal Research Center for Agriculture and Forestry (BBA) Koenigin-Luise-Str. 19 Tel: +49-30-8304-2220 14195 Berlin, Germany Fax: +49-30-8304-2203 Often wrong but never in doubt! The following section of this message contains a file attachment prepared for transmission using the Internet MIME message format. If you are using Pegasus Mail, or any another MIME-compliant system, you should be able to save it or view it from within your mailer. If you cannot, please ask your system administrator for assistance. ---- File information ----------- File: ParentChildABProblem.zip Date: 22 Feb 2003, 18:37 Size: 1639 bytes. Type: ZIP-archive