Re: lines in ER diagrams

[Lars Clausen <lrclause cs uiuc edu>]

On Wed, 23 Apr 2003, Anthony Ettinger wrote:
> Hi,
> 
> I'm using UML for my database diagrams, and I need to
> show entity relationships, it doesn't appear to
> support the standard notation for line
> endings/beginnings.
> 
> how do i show the following relationships ( "<" = crow
> foot):
> 
> 0 to many: ---0-<
> 1 to many: ---1-<
> 1 and only 1: ---1-1-
> 1 to 1: ----1-
> 0 or 1: ----0-1-
> 
>>From what I understand, the above line endings are to
> show those relationships, however I don't see these as
> choices in the line endings/beginnings in Dia.
> 
> Is there an equivalent?

Not really.  We're getting to where we can't just add more line endings
arbitrarily and have it be manageable -- the arrow list is just too long.
There was some talk about making a generic arrow model that would allow
complicated arrows to be designed by the user, but it hasn't gotten very
far, as far as I know.  The easiest way to do it right now would probably
be to code a line that understands those things, and have it draw multiple
line segments with text appropriately placed in between (or draw a normal
line and put the text over it, if the line should not be interrupted by the
numbers). 

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| Hårdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?