[fdo-internals] Request review of RFC 28 - AddStart/EndExpressionFunctions

[Jason Birch]

Unless there is a reason for the other cases, then that makes sense to me.
 
Personally, I'd prefer to see that as CenterX with point geometry being a degenerate case, but I understand that there may not be resources to return the centroids of the other geometry types at this point.  The nice thing about this is that it would set a convention for future useful functions like MinX, MaxX, etc...  
 
I guess the problem with this would be that throwing an exception would be less reasonable than it would be for a point-specific function.
 
Jason

________________________________

From: fdo-internals-bounces at lists.osgeo.org on behalf of Traian Stanev
Sent: Mon 2008-11-03 2:39 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Request review of RFC 28 - AddStart/EndExpressionFunctions



Yeah, may be just provide PointX()/PointY()/PointZ() functions which take a geometry as argument and throw an error for anything but points?

 

Traian

 

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Dan Stoica
Sent: Monday, November 03, 2008 5:24 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Request review of RFC 28 - Add Start/EndExpressionFunctions

 

What has the Start point so special except for the point features? For example, the START=END for simple polygons. 

Maybe this ECO should address only points? 

 

Dan.

 

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Greg Boone
Sent: Monday, November 03, 2008 2:53 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Request review of RFC 28 - Add Start/EndExpressionFunctions

 

Yes, Lines and Polygons do offer some difficulties. Also, the multi-geometry objects are also a little weird. I am open to suggestions on how to handle these types.

 

Greg

 

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
Sent: Thursday, October 23, 2008 12:34 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Request review of RFC 28 - Add Start/EndExpressionFunctions

 

That makes sense to me; I just wasn't sure what you would use the equivalent function for lines/polygons for.

 

Jason 

 

From: Robert Fortin
Subject: RE: [fdo-internals] Request review of RFC 28 - Add Start/EndExpressionFunctions

 

The use case: presents the ordinates of a point geometry as attribute in a data table.  This feature will help us achieve that.

You could also think it can be used to display the coordinate as labels as part of the symbology of a feature.  

Or you could use the StartZ to show the elevation of a point or apply a theme on it.

All these can't be done easily directly using the geometry attribute.