Re: Ternary Relationship cardinality

From: <miklesw_at_gmail.com>
Date: 19 Sep 2006 01:03:22 -0700
Message-ID: <1158653002.250096.72440@b28g2000cwb.googlegroups.com>

I know what cardinality is... and I know how to implement it

My problem is with the notation for a particular Ternary relationship.

(Supertype) [Parent]------[0..*]----- <Breeding> ----[1..1]--------[Child](subtype)

                        |-------------[0..*]------------|

The prob is when I use the N:1 notation..my first reaction would be to do something like this:

(Supertype) [Parent]------1-----
<Breeding>-----M-------[Child](subtype)

                        |-------------1------------|

However that doesn't make sense since ParentA can be related to Many ParentB's and viceversa. (don't think of the normal parent-child scenario.. it's a game and the relationship is the actual act of breeding)

PS I'm using Chen notation
PS2. After a day at work followed by 2 hours of transaction schedules .. I really couldn't give a damn about spelling&grammar..

Jonathan Leffler wrote:
> miklesw_at_gmail.com wrote:
> > I am working on an assignment which has 2 ternary relationship. I'm
> > can't figure out their cardinality.
> >
> > Maybe I am going through one of those mental blocks...
> >
> > Can someone give me some cardinality examples for N-ary relationships?
> > all the pics i found on google images don't include this..

> Cardinality = number of { rows, records, tuples } in a relation.

> Count the number of 'rows' in the table - that's the cardinality.

> Degree = number of { fields, columns, attributes }.

> Ternary relations have degree 3 (or 'are of degree 3').

> > My other option is to convert the 3-ary relationship into a weak
> > entity.. but I'll definitely loose marks on that

> You may also lose marks for misspelling 'lose' (and not using plurals,
> and using "I'm can't" for "I can't", etc).

> > [...]

>


> --

> Jonathan Leffler                   #include <disclaimer.h>

> Email: jleffler_at_earthlink.net, jleffler_at_us.ibm.com
> Guardian of DBD::Informix v2005.02 -- http://dbi.perl.org/
Received on Tue Sep 19 2006 - 03:03:22 CDT