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> > we are refusing to 'alter table' ? > Yes, I think users of relational systems often refuse to "alter table". For example, if there is an EMPLOYEE table with a NATIONALITY column, and a new requirement arrives to record more than one nationality in the case of employees with dual nationality, many data base adminstrators will be very reluctant to move the nationality data into a new table because of the effect on existing applications and the requirement to do a join every time you want the value of this attribute. XML is far more flexible in this regard. I believe that Bill Kent referred to this as a "one-to-one-and-a-bit" relationship (usually single-valued, occasionally multi-valued). They are very common, and very hard to handle properly in relational systems. Very often database designers just decide not to store the extra data because it is too inconvenient. In XML such values are very easy to represent. It's also much easier to hold properties-of-properties, such as the date on which each nationality was acquired, or the evidence that has been presented to prove this claim of nationality. Michael Kay http://www.saxonica.com/
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