The new properties you will find on a Table Relation in AX 2012 are:
Hua Chu from the AX team has written a Guideline document, explaining how these properties should be set for Relations you add to Tables in AX. Note that in AX 2012 most of the above information is not actually used at runtime. This is something that will happen in future releases.
I have modified the document so that it contains the information relevant for partners and customers extending the standard application and have uploaded it to my SkyDrive.
(Modified: Something weird is happening with SkyDrive, so I have also uploaded the file to my personal site - download)
The document requires certain knowledge of Entity Relationship Modeling (ERM) and UML notation.
This document is intended as a guideline only, and should not be used as a Step-by-Step instruction.
Changes to any of the described functionality might still happen before AX 2012 RTM.
Your feedback and questions are, as always, welcome.