[fdo-internals] Standardising FDO Schema's
robert.fortin at autodesk.com
Fri Aug 29 15:08:01 EDT 2008
As Orest said, FDO represents the data in different layer Datastore, Schema and Class. That's the rule. That's the standard.
The fact that some provider doesn't have/require schema doesn't mean we don't need a generic schema representation in FDO. It's up to the provider to say what this schema is named and what it maps to (e.g. default or something else). FDO doesn't impose rules around the name of the schema.
For example, removing the schema from SHP would result that you could have 2 flavors of shp depending on the connection. Connect to a single file and you get no schema. Connect to a directory and you get a schema name "default". SHP provider standardize to using "default" every time.
Also applications relies on that standard: there will be a schema and it will have a name. This result in consistant representation of the schemas and classes in a tree view for example. Changing this behavior has impacts on applications relying on that standard.
From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Mateusz Loskot
Sent: Friday, August 29, 2008 11:05 AM
To: FDO Internals Mail List
Subject: Re: [fdo-internals] Standardising FDO Schema's
Orest Halustchak wrote:
> 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
Thanks for the very in-depth explanation of schema naming issues.
But we still need a consistent way to define and describe all
possibilities of mapping and naming paths in text.
As Zac proves, using only separators (like ::, ~, etc.) is insufficient.
I think more self-describing approach is needed, perhaps we would use
XML or JSON for naming schemas?
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
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