modeling either/or relationship...
Hi!
I've got to model electrical constraints on a net of a pcb.
So, a net can be constrained either by layer,net class (and constraint name)
or constraint class (and constraint name).
The problem I have is that a constraint (with a name and a bunch of attributes)
can be either
- a "free constraint, adressed by layer, net class and name or
- a "bound constraint", adressed by the constraint class name.
A constraint cannot be both.
I can enforce this easily with a table constraint (id set1 xor id set2 is true), but
can I put this into an ER diagram too?
Lots of Greetings!
Volker
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