(my citation software stinks, so I must ask your forgiveness for always responding at the head of the thread) Further (along Eve's thread) it's interesting to note that without any use of ID and IDREF or KEY and KEYREF the instance documents resulting from the normalized (3NF) schema in Tim's example are non-normalized in at least one important sense. While the _schema_ has been normalized, the instance document still contains repeated records=objects=content. We've got an approach to normalize the XML Schema -- which is essentially like a database schema. What we do not have is an approach to normalize the _serialization_ of structures conformat to that schema. This is an area for innovation -- relational theory doesn't have a serialization problem. The database is everything. We've got two views here (kind of). An almost-database view (XSD) and (possibly many) serialized views of that. I agree that we in NDR need to tackle the issues around IDREF and friends, and further, that it needs to be done in the context of our normalization discussion. Also, I think that the issue of normalizing the serialization falls pretty cleanly under the NDRSC charter and expertise. With our joint work on normalization of the logical model as a starting point it seems like NDRSC ought to be able to go forth and tackle the serialization. -Bill