Thank you for such a detailed answer.
I've been studying Database Design for the last 3 months and 9 weeks of it has been EERD, in the last 4 weeks they introduced ORM. Our assement is to compare both methods for an imaginary project which we had to produce originally in EERD format with a few queries thrown in for fun. So I've spent my Christmas getting stuck in, but these were some questions I had floating around in my head and other forums couldn't answer them. It has been a heck of a steep learning curve in 4 to 5 weeks with other modules too.
For the multivalued attribute in Enhanced Entity Relationsal Modeling the entity is displayed in a double oval shape as below with prerequisite
This would then give the designer more choice as to how they wished to store the data, but in most cases it will become an entity itself and be stored as a reference with a unique id. This I feel is just a cop out, it lets the designer choose how to implement it allowing for potential missunderstanding. Looking at the diagram (which is not mine) I would think this could be a many to many relationship but who knows? Each course may only have one prerequisite. So EERD fails to show this then.
The composite valued attributes I see are more detailed in ORM, what did suprise me is the address is shown as an object and the values part of it. If I can eventually remove all my errors, I can then see how this would map to tables as I would guess the address object would be ignored and its values added to the person object. we shall see.
I'm using the free unsupported MS Visio tool at the moment but I noticed many drawings are different from the version I am using. Is it me or is this adding to the possiblity for misunderstanding. After a second year of "look here" / "look there" EERD notation confusion I hope ORM will keep its clarity.
Thanks again for your time.
Excellent resources, the NORMA tool should prove to be very powerfull/helpful in the future.