ER diagram: widget design: somewhat wrong

[Neil Zanella <nzanella cs mun ca>]

Hello,

1.
I would like to point out that ER diagrams, relationships are not 
necessarily binary: they can be ternary, or more generally, n-ary.
This means that it is simply not right to design the relationship
widget as having a 'left' and 'right' cardinality since there can
be more than one entity invloved.

2.
Furthermore, given any ER diagam used in the real world, it is
often impractical, even for binary relationships to have the
lines attached to them on opposite ends, so this assumption
is also incorrect. In general it should be possible to
attach the lines anywhere.

3.
Furthermore, notice how unnecessarily big the diamonds shaped
relationship widgets become when you enter text into them.
Don't you think it would be better to have a text area
for entering the relationship's name rather than a
single line text entry?

4.
Because of 3, some textbooks display the diamond as a six
sided polygon, like this:

  *************
 *             *
*               *
 *             *
  *************

I think dia should allow users to choose this option (notice
how the corresponding relationship figure uses up _much_ less space).

5.
Furthermore, why is it that dia does not allow its users to resize
entities and relationships?

6.
Why does the attribute icon have an 'R' inside it. This is absolutely
absurd: if anything it should be 'A' for attribute.

7.
Where is the ISA relationship figure for drawing 
specialization/generalization?

8.
Any why is it that I cannot have a staight oblique double line in dia?

For people interested in a standard reference on ER-modeling see either
Silbershatz or Ramakrishnan and Gehrke. There are also several other books
on relational database design that cover ER modeling.

Thanks!!!

Neil