Re: Drawing arcs on ER diagrams

From: Liz J <thejordanschangethistoanatsignclara.net>
Date: Thu, 19 Oct 2006 22:22:07 +0100
Message-ID: <1161292923.5643.0@despina.uk.clara.net>

"Frank van Bortel" <frank.van.bortel_at_gmail.com> wrote in message news:1161255739.418300.199470_at_m7g2000cwm.googlegroups.com...
>
> Frank van Bortel schreef:
>
>>
>> Arcs (in Oracle Designer) designate an exclusive OR to a super/subtype
>> entity relationship; aren't the circles simply to identify which
>> relationships are in the arc (as the drawing may become cluttered, and
>> more than one relation (line) may cross the arc)?
>>
>> If you are using Oracle Designer, the online help should explain this
>
> Yup - verified this. In Oracle Designer, when you have an entity A,
> with relationships to
> entities B, C and D, the arc may cross the relationships to B, C and D.
> If only B and D are
> Exclusive OR (in the arc), the circles will appear on the cross section
> of the relationship
> (lines) from A to B, and from A to D respectivily. The relationship to
> C may (or may not) cross
> with the arc, but will not have a circle, designating that the
> relationship between A and C is not
> part of the arc.
>
> Bit hard to explain without a picture, hope this makes sense.

Yes it does, thanks
>

Liz Received on Thu Oct 19 2006 - 16:22:07 CDT