[xquery-talk] Geospatial and XQuery?

[Xia Li]

Yes, I did write a paper which is a bit long story (more than 70 pages)
and I haven't got chance to cut it short and find a place to make it
public

 

Lisa

 

 

________________________________

From: Michael Kay [mailto:mhk at mhk.me.uk] 
Sent: Tuesday, October 04, 2005 10:47 AM
To: Xia Li; kfandre at netbox.com; talk at xquery.com
Subject: RE: [xquery-talk] Geospatial and XQuery?

 

Interesting. Did you write up this project?

 

Michael Kay

http://www.saxonica.com/

	 

	
________________________________


	From: Xia Li [mailto:xli at galdosinc.com] 
	Sent: 04 October 2005 19:06
	To: Michael Kay; kfandre at netbox.com; talk at xquery.com
	Subject: RE: [xquery-talk] Geospatial and XQuery?

	I did a bit exploration for extending XQuery to support query on
spatial, spatial temporal and spatial network data types defined in GML
(Geographic Markup Language) last year and an experimental
implementation study on a particular XQuery engine Saxon. I chose to add
all operations and functions defined for the GML types to the system
built-in function library. The way to achieve this in Saxon is to
register those functions and bind those function definitions with the
function call in query so that these function will be processed just
like any other system built-in functions. I remember one advantage of
this approach is that once integrating the functions into the existing
architecture we can focus on the implementation of computation logic of
the function itself and do not need to pay attention to do the type
checking for the parameters of the functions which requires the entire
implementation of XQuery sequence type matching. 

	 

	Another thing I found is that to support spatial network query,
one have to extend XQuery into a high order functional language. 

	 

	 

	Lisa

	 

	 

	
________________________________


	From: talk-bounces at xquery.com [mailto:talk-bounces at xquery.com]
On Behalf Of Michael Kay
	Sent: Tuesday, October 04, 2005 9:06 AM
	To: kfandre at netbox.com; talk at xquery.com
	Subject: RE: [xquery-talk] Geospatial and XQuery?

	 

	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.

	 

	Michael Kay

	http://www.saxonica.com/ 

		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.

		 

		-Kevin

		
		
		 

		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> 
		
		Hi,
		
		> 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.
		Java.
		
		Martin
		
		_______________________________________________
		talk at xquery.com
		http://xquery.com/mailman/listinfo/talk 

		 

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