database schema diagram

[Neil Zanella <nzanella cs mun ca>]

Hello,

I would like to be able to use dia to generate a database schema diagram
as documented in Silberschatz et al. and other database textbooks. The
schema diagram is a logical representation of the relational model
which is in turn derived from the conceptual ER-model design. The main
difference among the higher level ER-model and the lower level schema
diagram are that in the schema diagram each box represents a physical
table which is to be created in the database. Each box contains all
of the defining column names which make up the table with the primary
key separated from others via a horizontal line. One feature of the
schema diagram that the ER-model lacks is the ability to represent
foreign key constraints by means of arrows (if this were done in
the ER-model then there would be ambiguity as to what an arrow
might mean). In the ER-model an arrow points to a relationship
to indicate that for each participating entity there is exactly
one entity on the other side of the diamond shaped relationship.
On the other hand n the schema diagram an arrow points from some
column a to another column b in another table indicating that each
time a is not null it must appear as a value of b.

I think the implementation of schema diagrams would be similar to
the UML implementation except for the arrows should be able to
go in and out from each row, not from the object itself.

Thanks!

Neil