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Home -> Community -> Usenet -> c.d.o.misc -> Re: Drawing arcs on ER diagrams
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. Received on Thu Oct 19 2006 - 06:02:19 CDT