Foreign Keys

[frankk]

I had started with a Class diagram, using qualifiers on the associations, but it got messy quickly. I'll try stereotyping the attributes. (But a simple 'PK' and 'FK' would have been sooo nice and clean!)

[frankk]

I've added an "Abstract" DB type and this works nicely. But I have a new problem: when I draw an association, it appears as a line with two 'bend' handles instead of an arrow. The handles aren't selectable/draggable and I can't get rid of them. When I add a foreign key, one end of the line becomes an 'oval with legs' (sorry -- looks like a spaceship or satellite to me :-) and the other has two parallel lines crossing it. What the heck is this??

[frankk]

Hmm. The funny symbols seem to be caused by multiplicities on the association (generated by EA, I assume, since I didn't specify any). Removing the multiplicities clears the symbols, but I still can't get rid of the bends or get an arrowhead.

[Eve]

The default connector style of data modelling diagrams is one of the two data modelling conventions supported by EA.  You can change this on the diagram properties dialog.

[frankk]

Ahhhh :-)

Thanks.

[Paolo F Cantoni]

Yes, I want a conceptual model of a relational database. I simple Class diagram would suffice, but I would minimally like to be able to specify the keys and relationships.

Hi Frank,

We do this by specifying a new database type: ConceptualDB and specifying abstract datatypes within that.  That allows us to, effectively, create Data Modelling Entities.

It is appropriate that EA enforces that requirement that both tables be of the same database technology and that the columns are of the same datatype.

If you like , I can send you the appropriate reference data (it also includes a new code Language called Conceptual that provides the object equivalent - there is currently a bug in EA that means the two languages have to have different names)

HTH,
Paolo

[frankk]

Thanks, Paulo :-)

I'm still playing with my 'Abstract' (keeps it at the top of the list) DB type. It's still quite simple. I'd appreciate any non-obvious tips, though, if you've found anything tricky in using this method.