Re: Object-relational impedence
Date: Wed, 19 Mar 2008 12:53:08 -0700 (PDT)
On Mar 19, 1:15 pm, S Perryman <q..._at_q.com> wrote:
> Marshall wrote:
> > On Mar 19, 6:14 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> >>I am not sure how Eric gets from there to EAV, and I think that's highly
> >>speculative on Eric's part
> > Some of the things Mr. Perryman said led me to believe he was
> > discussing an EAV design. When I tried to either verify or dispel
> > my impression by reviewing the thread, I wasn't able to either way.
> > But I it seems I got a similar impression to Eric's.
> A standards body basically defined resource types of the form :
> type T
> // etc
> Attr1 = string
> Attr2 = Sequence<SomeNastyRecordType>
> There were 100+ resource types, and at least 100+ attr types.
> Which types had which attrs, and whether they were mandatory (belonging
> to all instances of a types) , or optional (present on a per-instance
> basis) was defined by the standards body (for the perversely-interested,
> here is one such spec for telecoms call data recording :http://www.itu.int/ITU-T/formal-language/gdmo/database/itu-t/q/q825/1...)
> This is what the developers were faced with.
> Store the info for each resource instance (and meta-info to allow the
> generation/processing of outgoing/incoming messages requesting/retrieving/
> setting the attr values) .
> Their mandated impl technology : SQL RDBMS.
> Steven Perryman
So they designed the data model to match the Standards document? IOW they did not do any design, but just tried to implement the standard in the RDBMS directly, right?
My first impression (coming in late to this thread) is that is what happened. And that is clearly an EAV design. Given a standard like that I think I would quickly decide to split types into different entities. A standard does not imply a design. The developers failed to do the proper design work. SO the impedance mismatch was between the developers and the RDBMS.
--- Magic Interface, Ltd. 440-498-3700 Hardware/Software AlchemyReceived on Wed Mar 19 2008 - 14:53:08 CDT