Re: Searching OO Associations with RDBMS Persistence Models
Date: 16 Jun 2006 13:03:30 -0700
Robert Martin wrote:
> 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.
Assume network is an [indirected] graph. Then logical connection is a path in the graph. There is nothing challenging in modelling graph in RDBMS and creating application objects that correspond to paths in a graph. Why "object id" is significant in this picture? | Received on Fri Jun 16 2006 - 22:03:30 CEST