Re: Unfathomable ERD Relationships

Jack,

Designer allows you to specify any kind of relationship you need. One need only grasp the notation. The only drawback I have encountered is not being able to specify, other than with text, precise cardinality, such as when there are exactly 2 or some such situation.

For a master/detail relationship where the master is required and the detail is optional with many, you should have an exaclty one symbol with a solid line on the master connection and a dashed line with crow's foot terminator on the detail side. This is supported in Designer. You can also do mutually exclusive and some other non-trivial relationships.

I am not sure if this addresses your concern or if you were just venting. Remember, the tool does not assign the cardinality, the user does. Hope it helps.

Steve
804-262-6332

In <4pk5hj$3i7_at_qed.pps.k12.or.us> jbotteron_at_pps.k12.or.us (Jack Botteron) writes:
>
>I am using Oracle Designer 1.1 for the first time. My previous
>experience with modeling has been with Knowledgware's IEW, using
>James Martin's diagramming conventions. Where did Oracle get its ERD
>diagram conventions? It is the most counter-intuitive convention I
>have ever seen. It is so confusing that even Oracle is confused.
>
>In order to learn Oracle's technique, I created two entities in their
>ER Diagrammer: A "purchase order" entity on the left, and a "line
>item" entity on the right. Then I created a relationship signifying
>that one PO MAY contain none or many line items, and a line item MUST
>belong to only one PO. The diagrammer drew a line with a crow's foot
>(cf) as follows: cf with a solid line on the left end, and a
>dotted line on the right end.
>
>When I created the report "Entity Relationship Diagram Details"
>the report seemed to accurately follow their conventions, but when I
>created the report "Relationships", the report displayed just the
>opposite cardinality and optionality. Also, the edit relationship
 dialog
>box is as confusing as the help screen associated with it. This
>really sucks. It seems obvious to me that Oracle is as confused with
>this convention as anybody else.
>
>Who in their right mind would put FROM cardinality on opposite ends
>of the FROM optionality? And then in their helps only talk about
>relationship ENDS, because they themselves cannot talk in terms of
>FROM and TO? The designer, and the Oracle person who adopted this
>convention should be hung from the highest yardarm at dawn.
>How can I draw diagrams that will be readable by users, when
>Oracle and I cannot fathom them? Is there a way out of this?
>
>Jack Botteron <jbotteron_at_pps.k12.or.us>
>Data Administrator, Portland Public Schools
>Portland, Oregon
Received on Tue Jun 11 1996 - 00:00:00 CEST