[wfs-dev] summary of changes from wfs 1.0 to 1.1?

[Panagiotis (Peter) A. Vretanos]

John Herring wrote:
> Peter, 
> 	Better yet, what is the OGC document number of the
> change request that removed join?  That should explain it. 
> 
> Regards,
> John
>

As far as I know there was no formal change proposal.  Clemens raised 
the issue of dynmaically encoding joins through the WFS interface and 
after discussion within the RWG, it was put to a vote and everyone 
present decided to remove joins.

Please note that I am not the RWG chair.  I am simply reporting what 
happened.

> 
> Peter, 
> 	Could you be more specific about why you are
> thinking of dropping joins. 
> 

Because it is unclear how two joined features would be composed in GML 
to generate a response and what the GML schema would even look like.

> 	A query without a join could not even do basic
> spatial query, so how is join-less WFS to do anything of
> value spatially other than some sort of "get features (with
> some attribute and type restrictions) within this (constant)
> widow?" Without a join, one of two spatial parameters of a
> spatial operation will have to be a constant. 
> 

Even though joins cannot be encoded in the WFS interface this does not 
mean that you cannot support joins (spatial or otherwise).  It simply 
means that you must create a view of the joined features (and a GML 
schema to encode it XML) and offer that view through the WFS.

I other words you cannot "dynamically" request that a WFS join two 
features; the join must be pre-specified in a GML application schema and 
that schema can be offered through the WFS.

> 	That is "mostly useless" as query. That cannot be
> what you mean. 
> 

I wouldn't say "mostly useless".  Most other OGC services (WMS, WCS, 
etc.) only support the type of query that you describe and they do 
useful work.  Don't they? :)

Ciao.

-- 
Panagiotis (Peter) A. Vretanos          CubeWerx Inc.
Big Kahuna (Senior Database Developer)  http://www.cubewerx.com
Tel. 416-701-1985 Fax. 416-701-9870     pvretano at cubewerx.com

"If you want to make an apple pie from scratch, you must first
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