Thanks Martin for the pointer to the Saxon web page on XQuery Update. That web
page says this:
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Saxon implements XQuery Update Facility 1.0, which reached Recommendation
status on 17 March 2011. All features, including optional features, are
implemented.

The XQuery Update specification defines a number of extensions to the XQuery
1.0 grammar. Saxon implements these as extensions to the XQuery 3.1 grammar.
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Huh? I'm confused.  What is that saying? Is it saying:

(a) Saxon implements XQuery Update 1.0 which is a superset of XQuery 1.0 which
is a superset of XPath 1.0

(b) Saxon implements XQuery Update 1.0 which is a superset of XQuery 3.1 which
is a superset of XPath 3.1

(c) Something else - what?

/Roger