Hello forumers!

So I am working on a project for a class, where I have to draft an ER diagram/model. I have the concept down, as it's not so hard. Entities, relationships, attributes, cardinality, etc etc. I've also worked on small examples as to practice making these diagrams, and I must say neither is it bad nor is it so boring either.

Now I am working on a project, the giant amongst us students. I am finding it rather difficult, and although I am not asking anyone to walk me through how to complete it, I was wondering if someone would be able to critique what I've got so far?

So the project describes the relationship between a Local Art Museum and Other Museums. These museums form the Arts Friends Circle (which is confusing me, because I don't think one could make that apparent in the ER diagram using the standard notation) and they have Art Objects. But each museum has Permanent Art Objects and Borrowed Art Objects as each museum borrows and loans from their Permanent Art Objects collection.

Each museum also has Exhibitions and Loyal Visitors who visit these exhibitions. The museums also have Staff.

Currently, I have these entities: Local Art Museum, Other Museums, Permanent Art Object, Borrowed Art Object, Exhibitions, Loyal Visitors, Visitors, and Staff.

There are some additional details that I am leaving out as I I know how to work with them properly.

So current, here is my model:

Local Art Museum 1 -----HAS---> * Permanent Art Objects

Local Art Museum 1 -----HAS---> * Borrowed Art Objects

Other Museums * ---- HAVE ---> * Permanent Art Objects, Borrowed Art Objects

Now this is where I get confused. For Permanent Art Objects and Borrowed Art Objects, they each have unique attributes(ie, for the latter, The name of the museum it was borrowed from, the date it was acquired, and the date to be returned).

It would make sense if there was only one Art Object, but with separate attributes. I know that each attribute can be broken down into sub-attributes, but maybe I am not seeing how it should be done.

It would be easy if I can say Local AM 1 borrows * Art Objects, but it gets confusing if the permanent and borrowed art objects are separate.

So what my ER diagram needs to show is that Local Art Museum has many Art Objects, that all museums borrows from these objects, that each museum has exhibitions and loyal visitors who can visit these exhibitions, and each museum has staff. It may be relevant to state that (well, state again) that each museum is part of a community called the Art Friends Circle.

http://s483.photobucket.com/user/nba4191/media/example.png.html?sort=3&o=0

Above is a link to a photo on PhotoBucket, which is my original starting draft for this diagram. It's very basic, and I did not notate my relationships properly, but that's OK, as I am just trying to show you what this is trying to look like.

So my questions that I am struggling with, are how do I have two Art Object entities, one borrowed and one permanent, and how do the museums 'trade' between each other? I am having an issue figuring the proper way to demonstrate that.

Again, I am not looking for someone to do this for me, but to pass on advice. In return, I'll make sure I always pass on my advice when I can and when the situation is appropriate.

Cheers