RE: [xml-dev] [main] SQL instead of XQuery

["Michael Kay" <mike@saxonica.com>]

> 
> 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/