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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>This is a very interesting discussion.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Let’s look at this from another angle.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The FDO schema itself is a logical schema. The provider is
responsible for mapping the logical schema to physical implementations.
Different physical formats have different concepts and constraints. Even
between RDBMS products, there are differences.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>From the FDO perspective, we have the following layers.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Data
store: This is actually the container or repository of an integrated set of objects.
Within a data store, objects are modeled by classes within one or more schemas.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Schema:
This is a logical grouping of classes. There is no specific constraint as to
how to group classes, but the grouping is usually based on the close
relationships between classes, e.g. a LandUse schema, a Transportation schema,
a WaterUtility schema, etc.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Classes:
Describes the type of a real world object.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Etc.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Consider this example.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> LandUse
Schema:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Classes:
Parcel, Park, Lake, Agricultural, Industrial, …<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Transportation
Schema:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Classes:
Interstate, Highway, Road, Railway, BikePath, …<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> WaterUtility
Schema:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Classes:
WaterPipe, WasteWaterPipe, Valve, …<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> GasUtility
Schema:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'> Classes:
Pipe, Valve, …<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Now, I may have a number of data stores that use the above:
CityOfDenver, CityOfBoulder, CityOfColoradoSprings, …<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The above is a logical schema. How could that be mapped to
physical schema? The discussion started with Oracle. Let’s say I have an
Oracle instance called ORCL. The main physical grouping mechanism that Oracle
has is an Oracle Owner. So, one mapping is that the FDO Data Store maps to
Oracle Owner, then FDO Schema.Class maps to table. That keeps the integrated
set of data within a single Oracle owner. Another mapping is to map FDO schema
to Oracle Owner, i.e. define Oracle owners LANDUSE, TRANSPORTATION, etc. But,
then how do we separate CityOfDenver parcels from CityOfBoulder parcels? I
could have DENVER_LANDUSE, BOULDER_LANDUSE, etc. There is a third mapping
possible, and that’s to use a separate Oracle instance for each data
store, but users may not want to set up separate physical instances for this purpose,
especially if they have a large number of data stores.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Orest.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Zac Spitzer<br>
<b>Sent:</b> Thursday, August 28, 2008 10:00 PM<br>
<b>To:</b> fdo-internals@lists.osgeo.org<br>
<b>Subject:</b> [fdo-internals] Standardising FDO Schema's<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<p class=MsoNormal>Hey everyone,<br>
<br>
I have written up some ideas on FDO schema's as they stand and making them<br>
provider agnostic and predictable across all FDO providers.<br>
<br>
<a
href="http://zacster.blogspot.com/2008/08/some-ponderings-on-fdo-schemas.html">http://zacster.blogspot.com/2008/08/some-ponderings-on-fdo-schemas.html</a><br>
<br>
Mateusz Loskot suggested I post this here to get some feedback and then <br>
maybe write it up into a RFC.<br>
<br>
z<br>
<br>
<br>
-- <br>
Zac Spitzer -<br>
<a href="http://zacster.blogspot.com">http://zacster.blogspot.com</a> (My Blog)<br>
+61 405 847 168<o:p></o:p></p>
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