Re: Designer/2000 ERD Cardinalities

jmjacobs_at_ix.netcom.com (Jeff Jacobs) wrote:

>rgordon_at_acpub.duke.edu (Robert Gordon) wrote:
 

>>Could someone please explain the cardinality symbols for D/2000 ERD's?
>>I am familiar with IDEF1X and IE symbologies, but I cannot figure this
>>out - particularly which end is which for the different symbols (and I
>>have RTFM)! Thanks
>>
>>
>>- Robert Gordon
>>
 

>The crow's foot/trident is the same as in IE notation for "more than one". D2K
>uses dashed and solid lines to indicate optionality/minimum cardinality. The
>line is divided into two "halves"; the half _closest_ to the entity indicates
>the optionality for that direction. Solid line is "mandatory", dashed is
>optional. So you have to combine the line half closest to the entity with the
>presence/absence of a crow's foot at the _other_ end to arrive at your
>optionality + maximum cardinality.
 

>The line type replaces the "o" and "|" in IE notation. The "|" in D2K is used
>to indicate that the relationship is part of the unique identifier.

>-JJ
 

> Jeffrey Jacobs & Associates

[Quoted] This is the opposite of what I initially thought. It seemed intuitive that the half of the line closer to the crows foot would indicate optionality at that end (like IE). BTW, is Oracle using a methodology I just haven't learned or did they make this up to confuse people?

Thanks Jeff

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• Robert Gordon