Well, uniqueness could be enforced by adding a <xsd:unique> or <xsd:key> element to the definition of modsType in the schema. Not to say it would be a good idea (kind of an unnatural way of doing things), but it would solve one of your problems while being partially backwards-compatible. The XPath expression matching a main title right now looks like "titleInfo[not(@type)]". As to whether every record should have a title, <name> and <subject> can be XLinks. These could point to MODS records themselves (under the v3 schema) without <titleInfo> subelements. If <titleInfo> were required in <mods>, each <name> or <subject> would have to be in its own document since a <modsCollection> can only have full MODS records and not isolated top-level elements as children. The minimum content model of a MODS record could be tightened up (as you observed earlier if it can contain only an empty <note> and be valid it might as well not contain anything), but it could remain a bit looser than "main entry". --Andy >>> [log in to unmask] 2004-01-22 11:55:45 >>> Andy, I agree that adding "type=main" is not a great solution. I've got only limited experience with XML schema, but my impression is that if you have a element that you wish to control (i.e. give a specific minOccurs to) or link to, then it needs to be distinguished at the element level and not at the attribute level.