Home -> Usenet -> comp.databases.theory -> Re: Searching OO Associations with RDBMS Persistence Models

Re: Searching OO Associations with RDBMS Persistence Models

From: Robert Martin <unclebob_at_objectmentor.com>
Date: Fri, 16 Jun 2006 08:37:11 -0400
Message-ID: <2006061608371116807-unclebob_at_objectmentorcom> 






On 2006-06-05 16:35:18 -0400, "Mikito Harakiri" 
<mikharakiri_nospaum_at_yahoo.com> said:


> Robert Martin wrote:




>> It's not a matter of preference.  Application objects are often complex

>> assemblies of many different tables and relationships, all of which

>> have their own keys.  Which of those keys is the identity of the

>> application object?

>> 

>> For example, I once worked on a network management system in which

>> circuits were terminated by CSUs.  There was a CSU table and a circuit

>> table.  Logical connections between parties could use many different

>> circuits.  The application objects that embodied these logical

>> connections were complex assemblies of circuits and CSUs.  They were

>> semantic elements that had identity; but they weren't database

>> entities, and so the concept of "key" was superfluous.


>> 

> ...




>> 

>> Sorry, what I mean is that the database keys are not unique identifiers

>> for the logical application entities.  For example the key for a

>> circuit could not be used to identify a logical connection.  A logical

>> connection is a semantic entity, composed of elements from the

>> database.  There is a need for these semantic entities to have


>> identities which are not just database keys.



> 
> Could you be more specific, please? You have
> 
> table Circuits (
> ...
> )
> 
> table CSVs (
> ...
> )
> 
> What important attributes are there? Sample data too (couple of records
> to make the matter clear would suffice).
> 
> Then, what application object looks like?
> 
> (Crossposted c.d.t, as I quit following c.o).





A logical connection between two endpoint is a list of circuits.  This 
application object is transient because the connections come and go.  
They aren't stored in the database.



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Received on Fri Jun 16 2006 - 14:37:11 CEST












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