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Re: ORM or JDBC?

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On 11-04-01 06:38 PM, Tom Anderson wrote:
> On Thu, 31 Mar 2011, Arved Sandstrom wrote:
> 
>> the relational data model is a _logical_ data model, not a conceptual
>> one that defines the semantics.
> 
> What's the difference between a logical model and a conceptual model?
> 
> tom
> 
Let's put it this way - I doubt you'll find an authoritative reference
that informs us exactly what is a conceptual data model, exactly what is
a logical data model, and exactly what is a physical data model. However
the terminology, and that division into three levels of abstraction of
data modeling, is quite common.

A conceptual model equates to a business model. You might have entities
for Person, Address, and LifeEvent, say. There is just enough
information in the description of each to support a _business-level_
discussion of relationships and identifying information and extra
information.

It's in the logical model that, assuming we are talking about a
relational logical data model, that we might say that Person has
person_id as a primary key, that there's a M:N between Person and
Address and we describe the join table, there's a 1:N between Person and
LifeEvent, we specify exactly what the tables are and what columns
exist, what columns are foreign keys, and so forth.

In a physical model not only do I already know that I'm using an RDBMS,
I know I'm using Oracle or SQL Server. I'm writing the details of my JPA
and deciding what my indexes are, and what the syntax is for a boolean
data type.

In the conceptual model there's no such thing as tables or columns, and
we're not overly worried about datatypes or about exactly how we are
going to define the primary key for Person. You should be able to take
your conceptual model and be able to choose something other than a
relational model as your logical data model, is the point.

AHS
-- 
That's not the recollection that I recall...All this information is
certainly in the hands of the auditor and we certainly await his report
to indicate what he deems has occurred.
-- Halifax, Nova Scotia mayor Peter Kelly, who is currently deeply in
the shit

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Re: ORM or JDBC? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-03-31 13:19 +1300
  Re: ORM or JDBC? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-03-31 20:16 -0300
    Re: ORM or JDBC? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-04-01 13:10 +1300
      Re: ORM or JDBC? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-04-01 20:12 -0300
        Re: ORM or JDBC? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-04-02 15:45 +1300
          Re: ORM or JDBC? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-04-02 09:21 -0300
    Re: ORM or JDBC? Tom Anderson <twic@urchin.earth.li> - 2011-04-01 22:38 +0100
      Re: ORM or JDBC? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-04-01 20:03 -0300
        Re: ORM or JDBC? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-04-02 15:44 +1300
          Re: ORM or JDBC? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-04-02 09:35 -0300
            Re: ORM or JDBC? Lew <noone@lewscanon.com> - 2011-04-02 10:25 -0400

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