[xquery-talk] Extend and override

Michael Kay mike at saxonica.com
Wed Aug 10 10:30:16 PDT 2011

On 10/08/2011 17:02, Tim Finney wrote:
> Hi Everyone,
> I'm interested to know how to do extension and override.
With XSLT ;-)

Seriously, I did a consultancy assignment with a big XQuery user and 
this was a major hassle. We invented some kind of machinery for building 
a query using variant versions of a library module to handle different 
scenarios, but we had to decide up front which version of the query to 
use in each run-time situation so it wasn't much fun.
> Can it be done in an elegant and bomb proof way? I'd like to know
> whether any of you know about good general approaches in this area.
In XQuery 3.0 we have dynamic function items and some of us still have 
hopes that we might get maps. (If maps aren't in the standard, they will 
certainly be in many implementations). With a map of function items you 
have something akin to a weakly-typed object as in Javascript, and you 
can use it to do dynamic despatch. It doesn't provide all that you are 
asking for, but at least there is no longer a brick wall.

Michael Kay

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