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List: postgis-users
Subject: RE: [postgis-users] Data Versioning?
From: "Chris G. Nicholas" <cgn () globexplorer ! com>
Date: 2003-07-14 15:06:29
Message-ID: 71E37EF6B7DCC1499CEA0316A2568328E79A35 () loki ! globexplorer ! com
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A few years back, we had a lot of discussion at OpenGIS mtgs about "long \
transactions." I personally walked away from these talks feeling it was pretty much \
the same set of issues CVS grapples with, except on a per-row basis for feature \
tables.
The typical scenario occurs where several technicians are trying to update/edit an \
entire coverage and can't "lock" the entire table, the most basic reason that others \
need to be able to redraw their screens. So they do "long transactions" - i.e. check \
out an entire copy, make their edits, and perform some form of a "merge" operation \
later on.
In practice, this sort of thing has far more to do with careful database design and \
organizational procedure(s) than any catch-all 'feature' in the spatial database. The \
most basic questions, for this or any other enterprise workflow, come to bear: Who is \
authorized to make such edits? What is the source data for the updates; \
orthophotography? If so, what scene/frame/date was the image, and what client \
software was used? etc. etc. etc.
Chris Nicholas
GlobeXplorer
-----Original Message-----
From: Jeff McKenna [mailto:mckenna@dmsolutions.ca]
Sent: Mon 7/14/2003 5:45 AM
To: PostGIS Users Discussion
Cc:
Subject: Re: [postgis-users] Data Versioning?
Thank you everyone for your replies to my spatial versioning question.
It's given me lots to think about. cya.
Jeff
Paul Ramsey wrote:
> Hi Jeff,
> I'll just finish off the Refractions tag-teaming of you :)
> I am writing from the Heart of Darkness itself, the ESRI UC, so I know
> whereof I speak, when I say: Jeff, free your mind! Do not confuse the
> particular terminology and implementation of a vendor with the application
> of a broader concept. ArcSDE versioning is a particular application of a
> form of spatio-temporal database schema. But it is not the only possible
> application, and it may not fit the needs of every user -- Chris has given
> some examples of change tracking which go well beyond the ArcSDE paradigm,
> but which *can* be supported through a well designed database schema.
> Remember, at root, all that ArcSDE "versioning" is, is a particular schema
> implemented in the RDBMS, and managed via the ArcSDE middleware. You can go
> into your ArcSDE geodatabase and interrogate the tables, see how they
> modelled the particular problem.
> Here in the Heart of Darkness, it is easy to forget that GIS transcends
> the particular boundaries and terminology used by ESRI, but it does.
> Yours,
> Paul
>
>
> Quoting Jeff McKenna <mckenna@dmsolutions.ca>:
>
>
> > I guess I was hoping to hear that PostGIS/PostgreSQL already handled
> > spatial data versioning similar to ArcSDE.
> > I understand the concept of 'meta tables' storing extra timestamp info,
> > but are there examples of this already in use out there? Has anyone
> > been successful in implementing spatial data versioning with
> > PostGIS/PostgreSQL???? (we deal with large datasets and this would
> > impact the way we do things bigtime)
> >
> > thanks.
> >
>
>
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users@postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>
--
Jeff McKenna
GIS Specialist
DM Solutions Group Inc.
http://www.dmsolutions.ca
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