Are Updates really needed in XQuery?

["Brian Vickery" <macacos@linkline.com>]

I have a simple question, "Why do we need updates as part of the XQuery
language at all?"

I have read the latest XQuery Update proposal (from the "XQuery Update
Proposal" by Patrick Lehti) and the older XUpdate WD.  I come from a
database background and view updates as imperative to the XQuery/XPath
language, but can't state "why".  I'm getting a lot of grief regarding
having Updates at all.  The types of "inserts" and "deletes" typically shown
are just adding/deleting a document from a "collection" (if collections
existed and they should IMHO).

Some examples are:

1.  If I have a collection of XML invoices why would I ever want to update
these?  An invoice is written once and never changed!

2.  If I have a document centric collection of XML document I would most
likely version each document, thus why do we need updates?

3.  If I have all my business contacts (companies I do business with) stored
in an XML collection, why wouldn't I just do a complete replace if I wanted
to change a companies name or address?

Does anyone have any real life scenarios/business cases that "MUST" have
updates?

thanks,