Release of the GCX XQuery EngineQ

[Michael Kay]

> Thanks for the pointer to DataDirect, I didn't know they had 
> projection implemented. I've been looking a bit into 
> optimization techniques for DOM trees, and came across the 
> TinyTree model from Saxon. I  was wondering whether you plan 
> to keep extending it.

The TinyTree model has been stable for a while and seems to work pretty
well. The main thing coming up that could cause a change is the need to
support updates. Because TinyTree gains much of its efficiency by assuming
read-only access, I suspect I will keep the TinyTree for read-only use
cases, and use a more conventional linked-object model for the cases where
updates are required.

Another thing I keep under review is whether to store typed values in the
TinyTree as well as (or even instead of) string values. There are certainly
some use cases where storing typed values rather than recalculating them on
demand would give benefits - but there are many more cases where it would
not.

Michael Kay
http://www.saxonica.com/