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We have been practising versioning as we are forced to track back
changes in land property map data into every detail. <br>
<br>
We practise it on the database level. Every single object is stored
with information on "creation" and "deletion", in fact "deletion" means
only setting the object as "historical" and changing an attibute like
"delete_date"<br>
<br>
When retrieving data, we use SQL Statements like <br>
<br>
"select attribute from table where ..... and delete_date >
"today"::date ( or something like that; don't care about my syntax
errors..)<br>
<br>
Using this way, we can even read differential data by using the date
information in select statements. <br>
<br>
However, we have been using this principle yet only for a PostgreSQL
(with geometrical datatypes NOT from PostGIS) database and feed the
results into our own applications which are not based on standard GIS
products. We cared a lot about the design of the database table
structure. <br>
<br>
Works very well for our needs. <br>
<br>
Greetings, <br>
<br>
Hubert<br>
<br>
<br>
<br>
<blockquote type="cite" cite="mid001501c34688$72891970$1602a8c0@tweety">
<pre wrap="">ArcSDE implements versioning at the server (read SDE software) level.
The database tier has no inherent "versioning" capability, regardless of
whether it is running on Oracle, Informix or Brand X. Versioning is
implemented using "delta" tables that track changes (adds and deletes)
across versions. There are a slew of other tables (what I call "meta"
tables) that make up the ArcSDE schema.
My guess is that a middle tier would be required between
PostgreSQL/PostGIS and the client to implement a versioning scheme
similar to ArcSDE.
-gary
-----Original Message-----
Subject: Re: [postgis-users] Data Versioning?
SDE is ESRIs Spatial Database Engine. It supports versioning for
GeoSpatial data the same way that CVS does this for code. CVS will not
work for this purpose, as Spatial Data stored in PostGIS is not stored
in flat text files like source code. Postgres / PostGIS would need to
support this directly.
I don't have the answer to the question, but am also very interested to
know if Postgres/PostGIS support any form of geospatial data versioning.
I am also curious to know if it supports long transactions. I should
probably RTFM before asking though.
--Craig
----- Original Message -----
From: "Rich Shepard" <a class="moz-txt-link-rfc2396E" href="mailto:rshepard@appl-ecosys.com"><rshepard@appl-ecosys.com></a>
To: "PostGIS Users Discussion" <a class="moz-txt-link-rfc2396E" href="mailto:postgis-users@postgis.refractions.net"><postgis-users@postgis.refractions.net></a>
Sent: July 09, 2003 3:36 PM
Subject: Re: [postgis-users] Data Versioning?
</pre>
<blockquote type="cite">
<pre wrap="">On Wed, 9 Jul 2003, Jeff McKenna wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Pardon my beginner question, but I am trying to find out how
PostGIS/PostgreSQL handles data versioning. Myself I am familiar
with SDE, but would love to find an open source alternative to
versioning
</pre>
</blockquote>
</blockquote>
<pre wrap=""><!---->large
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">datasets. Does PostGIS handle data versioning? If not, are there
plans for this in the future? Are there any documents/past email
postings regarding this? Thanks.
</pre>
</blockquote>
<pre wrap="">Jeff,
I've no idea what SDE might be, but there's always CVS. This is used
</pre>
</blockquote>
<pre wrap=""><!---->
</pre>
<blockquote type="cite">
<pre wrap="">primarily for source code development projects, but I've used it for
document development, too. So, I imagine that one could check in and
out different data sets, too.
Rich
Dr. Richard B. Shepard, President
Applied Ecosystem Services, Inc. (TM)
</pre>
</blockquote>
<pre wrap=""><!---->
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</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
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Dr.-Ing. Hubert Fröhlich
Bezirksfinanzdirektion München
Alexandrastr. 3, D-80538 München, GERMANY
Tel. :+49 (0)89 / 2190 - 2980
Fax :+49 (0)89 / 2190 - 2459
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