How do I create an attribute type with a link in an artifact type?

You don't need to create anything for those 2 types, it's predefined for you. I believe the design tool (e.g. Rhapsody) to requirements uses the Satisfies link type. I know Implements is for work items and validates is for tested by. To create the links you would go into RQM for example and invoke the link generation GUI from within a test case and it would automatically use the validates by link type.

In DNG you can add the columns to your views to see names of test cases etc... of what is linked to your artifacts. Again no need to do anything in DNG to enable this, it's predefined for these 2 link types.

You are very close, under the Manage Project Properties in the Link Types tab is where you would define additional relationships that aren't already provided for you. Then when you are in your artifacts/modules you can insert columns which are either attributes or link types or both.

Thank you Alex, but I already got that far.  I can see the two link types I want: Implemented By and Validated By.  They are listed under Link Types with Name, Relationship Labels, and RDF URI.  The problem is that I cannot select either of them.  I don't know how to add them to the Artifact type I have.  If I select "+ Add..." it just tells me that the link type already exists.

If instructions for doing this are documented somewhere, please point me to them.  So far, I am finding this product to be very poorly documented.  I wish I had a manual, either paper or on-line.

These 2 types are specific to RTC and RQM respectively that is why you can't assign them to the artifacts, for other link types that you define you assign them to artifacts as preferred link types.

Implemented by would be a link from an RTC work item and validated by would be a link from the test case in RQM.