Need help of a DTD Expert

Hi, Because I am starting Foreign Keys additions to MDB2_Schema I am updating its documentation and XML Schema as well. Currently we have a very lax DTD that I would like to improve. As it has being so difficult to find a good/complete DTD reference I am appealing to anyone of you that have any experience with DTDs to give me a hand. I am facing problems such as : the element table can have a literal string sometimes or a well formed sequence of children. current definition: <!ELEMENT table (#PCDATA | name | was? | description? | comments? | declaration | initialization?)*> desired definition: <!ELEMENT table (#PCDATA | name , was? , description? , comments? , declaration , initialization?)*> it doesn't accepts commas in mixed elements though. I don't think using '|" (or) here is a good approach as it would allow something not desirable like: <table><name>foo</name></table> note that the element "declaration" is required. thanks in advance, iGor.