[fdo-internals] RE: [mapguide-internals] FDO RFC 43 - Standard FDO Class Naming Conventions

Orest Halustchak orest.halustchak at autodesk.com
Wed Oct 28 08:56:34 EDT 2009


Note that there is another qualifier that should be taken into account in these discussions and that is the datastore name. There are really three levels of qualification: datastore name, schema name, class name. So, cases where it is suggested to use the file name as the schema name, if the file name is already used for the datastore name, it doesn't have to be used again for the schema name.

An issue with rdbms is that some such as SQL Server include the three levels of database, schema, and table. Others such as Oracle do not. So in the Oracle case if we map the datastore name to the Oracle user/schema, then we should not also use Oracle user/schema for FDO schema.

Consider this example.
	FDO Datastore = CityOfNewYork
		FDO Schema = LandBase
			Class = Parcel
			Class = Road
		FDO Schema = Water
			Class = Pipe
			Class = Valve
		FDO Schema = Gas
			Class = Pipe

	FDO Datastore = CityOfAlbany
		Same schemas and classes

We don't want to mix up the parcels from CityOfNewYork with the parcles from CityOfAlbany, those should be in separate tables. Having the Oracle schema name as LandBase, Water, and Gas doesn't handle this.

Also, about the ~ColumnName convention being used for geometry columns, note that FDO does allow more than one geometry column per class with one flagged as the main geometry. I wouldn't want to require that these have to be exposed as separate feature classes.


-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Haris Kurtagic
Sent: Wednesday, October 28, 2009 6:07 AM
To: 'FDO Internals Mail List'
Subject: [fdo-internals] RE: [mapguide-internals] FDO RFC 43 - Standard FDO Class Naming Conventions

there is another important case which is not covered in RFC.
Same table name in multiple schemas. Also, how to not mess up when users
logs using different credentials.

One way to solve that could be to always use rdbms schema name as fdo schema

I believe it is absolutely necessary that application using FDO to access
rdbms can be sure exactly which table and column it is accessing.
Because what FDO provider sees when connects to rdbms can change regarding
which credentials are used to connect to rdbms. That menas that on same
database it can see only one table, or two tables (same name) in two schemas
or even one or more geometry columns in table.

I am not keen on current naming in King.Oracle with this ~ sign, but I am
very pleased that when using King.Oracle and FDO class trough it, I know
every time exactly which Oracle schema, table and column I am hitting.

Just when wanted to finish something else from RFC:
"Class names for databases are normally tablename, unless qualified which
then has ~COLUMN_NAME appended. (if the are multiple geometries, FDO
requires to know which one is the identifier)"

In King.Oracle ~COLUMN_NAME is appened to make sure resulting name would be
unique. Which actuall oracle column is used is not parsed from name of class
but it is kept inside provider. ~COLUMN_NAME could be anything.


-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org
[mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Zac Spitzer
Sent: Wednesday, October 28, 2009 9:45 AM
To: FDO Internals Mail List; MapGuide Internals Mail List
Subject: [mapguide-internals] FDO RFC 43 - Standard FDO Class Naming

I have posted RFC 43 for review


Zac Spitzer -
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