Re: ER diagram?

Is there a description of the ER notation that uses the symbols in the ER
sheet included with Dia?

Not that I know of.

I'm not quite familiar with this notation set-- it
seems to be a conglomeration of some elements from several different notations.

I think it is based on the original ER notation which was described by P. Chen in 1976, then enhanced by 
others.  It's well documented in relational database textbooks.  One is Korth, H. F., and A. Silberschatz, 
*Database System Concepts*, 1991, 2nd ed., pp. 34-47.  Another is Elmasri, R., and S. Navathe, *Fundamentals 
of Database Systems*, 1994, pp. 57-63.  I'm not sure who devised it originally.
For instance, if I use the crow-foot to represent cardinality, how do I
represent optionality? The notation I'm familiar with (arbitrary) would have a
crow-foot with a line or a crow-foot with a hollow circle.

I'm not familiar with IE ("crow's foot") notation, but if I understand your question, I think it's 
represented with a single line (as opposed to two parallel lines) for "partial participation".

Also, I've browsed the mailing list a bit, and it seems that many (most?)
people who are doing ER diagramming are using the UML sheet, rather than the
ER sheet. Is that because the ER shapes don't allow direct inclusion of
Attributes _in_ the Entities?

That is the main reason I use the UML notation instead of ER, yes.


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]