[postgis-users] Re: postgis-users Digest, Vol 67, Issue 22

[Ragi Y. Burhum]

 I guess this is a good time for me to give my two cents.

A few disclaimers and background : Until last year, I worked at ESRI. I
contributed with some of bug fixes for the PostgreSQL/PostGIS support in the
ArcObjects side of things. I have also been using PostgreSQL and PostGIS for
*many* years now. I follow many blogs (including yours Paul) but don't
usually respond for obvious reasons. I have been known to circulate some
various postings of criticism among places I have worked (or am working) at
like ESRI, MS, etc. Chances are, you are running some of my code in some
O.S. application and you don't even know it thanks to the beauty of Internet
anonymity :)

That being said, here are a few answers to some of your questions:


>
> Date: Sat, 24 May 2008 02:05:14 +0800
> From: Tim Bowden <tim.bowden at westnet.com.au>
> Subject: Re: [postgis-users] PostgreSQL/PostGIS and ArcGIS Server 9.3
> To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
> Message-ID: <1211565914.5940.108.camel at edoras>
> Content-Type: text/plain
>
> On Fri, 2008-05-23 at 10:15 -0700, Paul Ramsey wrote:
> >> SDE allows you to use ArcMap as a client. That's the main value
> proposition.
> >>


That's not entirely accurate. ArcSDE allows you to use the ArcGIS ArcObjects
GeoDatabase Layer. This includes the ArcGIS Server, ArcMap, ArcCatalog,
ArcEngine Apps, and everything that is supported by that layer: Raster, TIN,
Topology, Versioning, Geometric Networks, Network Datasets, Representations
Layers, Annotations, Dimension Feature Classes, Cadastral Fabrics to name a
few.


>> Secondarily, there's some stuff, most particularly versioning, that
>> they implement by managing extra metadata in side tables.  This is
>> where your concern regarding 3rd party edits to PostGIS data come to
>> reality. If you start mucking with the data, particularly versioned
>> data, outside the SDE environment, you can put it into an inconsistent
>> state.
Mostly everything is implemented by managing extra metadata tables. However,
that doesn't mean that there is not a mechanism for you to work with those
tables directly. As far as versioning goes, multiversion views allow you to
modify the simple features in versioned tables through the SQL prompt
directly and allowing the data to remain consistent.


> Ok, versioning is potentially quite valuable, depending on how well it's
> implemented.  I imagine the editing problem exists for both inserts and
> updates.  Pity, as it would be nice to at least put new geometries
> directly into PostGIS without upsetting SDE.

You can do this with Simple Features. ArcSDE allows you to 'configure' how
you want to store your geometry in the underlying database. Do you want to
use the ESRI PostgreSQL type? Do you want to use the PostGIS type? etc. Your
choice will have different advantages/disadvantages.

>> Also, you need some knowledge of the SDE scheme in order to properly
>> *read* the information out of a versioned system with a 3rd party
>> tool, since the data in the tables will include shapes from multiple
>> versions.
>>
>So if I've understood correctly, if you aren't interested in versions,
>but only the latest and greatest geometries, you should be fine doing a
>direct read of the PostGIS geometries.
See above for multiversioned views in regard to versioning. As long as you
are not using ESRI Complex Feature Types (Topology, Geometric Networks, etc)
you are correct.

>> In general, if you restrict yourself ot reading with 3rd party tools
>> and writing with ESRI tools, or non-ESRI tools working through the SDE
>> API, you should be safe.
>>

True.

>> Yes, using SDE effectively castrates the spatial database. It still
>> walks and talks, but it's a shell of the man it was before.
>>

This is where we disagree. Although hammers are good, sometimes you need a
screwdriver. The right tool for the right job.

>Ah, but a much cheaper shell than previously available to SDE users
>(with at least 87%(?) of the performance as I vaguely recall from some
>semi-relevant benchmark study)!
Oh... so relative.
Anyway guys, thanks for the great work in PostGIS. Some of us use it and
even evangelize extensively on certain situations... despite getting stabbed
with hate comments every once in awhile.

Can't we all just get along? :-)

- Ragi Yaser Burhum
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