Question 1:  For simplicity purposes, are you saying that the relationship between assignment and rubric is 1-to-many?  I feel like it's a many-to-many because one assignment can have many rubrics and each rubric can be associated with many assignments.

Question 2:  Each criterion has a name, and for each rating value, a description of the performance quality that warrants the rating.  Are you saying...

Each criterion has a name (type: string)

Each criterion has a rating (type: integer)

Each criterion has a description for a specific rating(type: string) ?

Thanks