GNOME Bugzilla – Bug 57386
Enhancement Request: Better ER diagrams
Last modified: 2009-08-15 18:40:50 UTC
The ER diagrams of dia don't match the ER diagrams I've seen in textbooks (and which seem much better). The diagrams I'm thinking of have lines with interesting connectors (small forks, bubbles, etc) to reflect many-to-one, one-to-one, nullable, etc., relationships between entities. I've enclosed the following attempt at ascii art to show you: ------- ------- | |\ | | | emp |----o-| org | | |/ | | ------- ------- This diagram says that there's a many-to-one relationship between employees and organizations, and that every employee must belong to some organization, but that some organizations might have no employees. Is anybody familiar with this kind of diagram? M
The bubble is already there, if you use a normal zigzagline and select the proper arrowtype. The fork is still a problem. Is there some online documentation with a kind of standard for these things?
Mass reassign of bugs to dia-maint@bugzilla.gnome.org.
Indeed, in "J2EE 3rd Ed" from O'Reilly, there are plenty of very nice ER diagrams with the thing you rendered in ASCII above. Now that it's less painful to add an arrow type, it may be useful to spot what's in this book, and add at least these.
The ER diagram that you're asking for is just another ER notation. I think opinion the notation used in DIA is more descriptive. In fact there are several ER flavors. If you're looking for textbooks in "Fundamentals of the database systems" by Elmasri and Navathe the current notation is used.
Crow's foot arrow has been added, as well as several other interesting arrows. If you can point us at an online picture, or attach one, we can look at what else is desired.
I have that book (3rd edition). Looking at pages 97 and 319, there 2 ER diagrams, but both can be done in current Dia. If dia developers agree, I propose to close this.
I don't have the book but like closing bugs :-)