Now I have a question regarding relationships between tables in the 2013 Data Model. It seems that when I create a relationship between 2 lookup tables, power pivot will automatically make it "Inactive". Why is that? I haven't read anything about Inactive relationships, or that they can exist. In the Diagram view, it shows as a dotted line, and in the Manage relationships dialog box, it shows the status as inactive. Why are some relationships inactivated?