[xquery-talk] Geospatial and XQuery?
mhk at mhk.me.uk
Tue Oct 4 19:05:56 PDT 2005
Good point: though I don't think it proves that you need such functions in
the core (standardized) language, only that you need the XQuery engine to be
aware of the functions so that it can optimize them.
Without a standard how would an XQuery optimizer know how to deal with a
third-party geospatial function? Execution plans would differ drastically
depending on the cost or absence of spatial indexes, etc. I recall seeing a
sepecialized XQuery extension standard for text search. It seems like
there's an opprotunity to do the same with geospatial data, especially if it
was written w.r.t common XML geospatial data formats.
On 10/4/05, Martin Probst <martin at x-hive.com> wrote:
Real-To: Martin Probst <martin at x-hive.com>
Real-Cc: talk at xquery.com <mailto:talk at xquery.com>
> If so, what would the geospatial functions look like in a query?
> Have any of the XQuery or XML database products (commercial or open-
> source) implemented geospatial functions ahead of the spec? If so,
> what do these look like?
X-Hive/DB is used by Galdos (http://www.galdosinc.com/) in Cartalinea.
They did not need custom functions that much as fast range queries on
XML attributes, e.g. to find certain specific elements that are within
(in the spatial, not in the XML sense) a set of coordinates.
So basically they needed fast range index lookups on XQuery, XPointer
and XPath queries.
I don't think there is a need for a standardisation on specific
geospatial functions, especially as you can extend nearly every XQuery
implementation with your own custom functions so you can use these
custom functions as an adaptor-like wrapper around a library in e.g.
talk at xquery.com
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