[postgis] GML vs. WKT

Rob Hranac robhranac at vfny.org
Thu Feb 14 18:15:58 PST 2002


Hi Guys,

I have a question about the syntax of your geometry functions.  Example:
GeometryFromText('LINESTRING(191232 243118,191108 243242)',-1)

You mention that this is the WKT description of OGC primitives.  Note that
your geometry functions separate coordinates by a space delimiter and
coordinate tuples by a comma delimiter.  This is the exact opposite of
common practice in the GML world.  Although GML allows you to specify any
delimiter you want for each (in the 'ts' and 'cs' attributes of the
<coordinates> element), the default is that coordinates are separated by
commas and points/tuples by spaces.  I know almost nothing about WKT (and a
quick search on the pristinely organized OGC website showed nothing), but is
the default syntax for it's delimiters, then, the exact opposite of GML?

If not, ignore the rest, but if it is... It is a safe bet that the GML
default will become a near-standard in most applications.  Certainly not a
show stopper, but it does make life slightly more difficult GML converters
such as myself; it is probably a fair assumption that GML converters will
someday comprise a large portion of your user base.  Given, this you might
think about switching your delimiters, unless I am missing something in WKT
or OGC SQL.  

Remain a big Postgis fan, by the way.  Will soon spam this list with a beta
announcement for my open source WFS, which serves exclusively from Postgis.
It is getting tested in OWS1 and Postgis is holding up really well.

Regards,
> Rob Hranac
> Vision for New York
> 377 Broadway
> NY, NY  10013
> tel: 212.219.6052
> fax: 212.219.6006
> eml: robhranac at vfny.org
> web: www.vfny.org
> 
> 

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