ERD - Associate attribute with Relationship

[Anthony Byrne]

Newbie question.  In an ERD I have created two entities and a relationship between the two.  How do I add attributes to the relationship?

[Sunshine]

You can add attributes to classes but not relationships. In the diagram right click and select "attributes" you get a dialog box up from where you can add attributes. Use New and Save buttons to add and update attributes to that class/entity.
I'm sure this is in the manual under Modelling Fundamentals>Elements>Attributes.
Ah yes here it is
http://www.sparxsystems.com/enterprise_architect_user_guide/9.3/modeling_basics/attributes.html

If you are thinking of changing the properties on the relationship such as cardinality i.e. one to many etc. then right click on relationship and select properties.

May be try reading the help next time you might find what you are looking for there.

[Anthony Byrne]

Thanks.  I did read the help    It seems to show a relationship with an associated attribute.

http://www.sparxsystems.com/enterprise_architect_user_guide/9.3/domain_based_models/entity_relationship_diagrams_e.html

(if the img doesn't render look it up in the offline help .chm)

You've sent me a link for a Data Modelling Diagram.  I am creating an Entity Relationship Diagram.

[Sunshine]

Ah right I see where your coming from now. Some folk refer to data models as ERD's too so hence the confusion.

Looking at that example on wikipedia
http://en.wikipedia.org/wiki/File:ER_Diagram_MMORPG.png I see the example of the relationship between Character and Account has attributes attached and I guess that's the type of thing your trying to achieve.

Unfortunately the bad news is that the implementation of relationship in Sparx EA of ERD uses a connector underneath and as far as I'm aware you can't attach another connector. Thus thats why you can't connect attributes to relationships in an ERD. Can't blame you for falling into that trap. May be this is an implementation flaw of ERD by Sparx Systems? Anyway looking at the example ERD diagram in Sparx EA help (ver 8.0) it seems they use the N-ary association between projects and employees then connect an attribute to that N-ary association called hours. The N-ary association is implemented as an object underneath in the UML profile and you can attach connectors to objects.

Well hope that helps  

Good luck.

[Anthony Byrne]

The n-ary association works for my needs.  Thanks for taking time to look at this.

[Sunshine]

No problem happy to help.