OWS-4 has had a related discussion in the GPW thread. It deals with
what is formerly known as the Data Aggregation Service (DAS) and
currently known as the GML Feature Fusion Service (FFS).
You can read the related page at:
https://portal.opengeospatial.org/wiki/twiki/bin/view/OWS4/GMLFeatureFus
ionService
The page originally started as documentation of the DAS/FFS interface
but moved on to dealing with joining features and discusses some of the
issues.
Cheers,
--
Steven Keens
PCI Geomatics Committed to Image-Centric Excellence
-----Original Message-----
From: wfs-dev-bounces+keens=pcigeomatics.com@anonymised.com
[mailto:wfs-dev-bounces+keens=pcigeomatics.com@anonymised.com] On
Behalf Of Panagiotis (Peter) A. Vretanos
Sent: Monday, October 16, 2006 4:39 PM
To: John Herring
Cc: 'Chris Holmes'; geoserver-devel@lists.sourceforge.net; wfs-
dev@anonymised.com; 'Ian Turton'
Subject: Re: [wfs-dev] summary of changes from wfs 1.0 to 1.1?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@anonymised.com"If you want to make an apple pie from scratch, you must first
create the universe." -- Carl Sagan
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