Hello Claudio,

>> > - the catalog (system tables) lives in its own schema
>> (don't know how
>> > relevant it's, but I found it in other products)
>>
>> Mostly "system" ;-)
>
> I found the SQL standard provides "definition_schema" (internal tables,
> available to the system only)

Ah.

>and "information_schema" (the available views
> that the user can query to get metadata).

Yes, these days, SQL Server 2005 and MySQL provide such views,
extended with their own set of views and/or columns to make things fully
available to the user.

>
>> > - a schema can have security (and new privileges are needed
>> regarding the
>> > right to execute DDL, anyway)
>>
>> A "user" in the database (not server wide) is automatically a
>> "schema" in
>> SQL Server. Not sure if this is a requirement or even wanted as such.
>
> But I think this changes in SQL Server 2005.
> http://msdn.microsoft.com/en-us/library/ms190387.aspx
> says "Schemas are no longer equivalent to database users".

Correct, as in that you can create additional schemas, not bound
to users. Yet, a user (or role) has a default schema created.

>> > Now, who sees schemas as an urgent need and why?
>>
>> In large databases, having schemas as namespaces can be very useful,
>> especially given the maximum of characters that can be used for
>> Firebird object names.
>
> Since Oracle uses (or used) shorter names (28 characters), I can see how
> important the feature was for Oracle, too.
> ;-)

;-)

Either way, I think you can understand the use of Schemas to group
items together.

With regards,

Martijn Tonies
Upscene Productions
http://www.upscene.com

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