We have a bunch of locally developed LTI tools and we are in the process of switching them from 1.1 to 1.3.  We have a few tools where we want to differentiate between an Instructor and a TeachingAssistant, but that is not easily done since the one is a sub-role of the other.  Our use case is to grant the highest level of access that the user could have, so we start with admin and work our way down.

So, for example when an instructor launches, the role data has 

http://purl.imsglobal.org/vocab/lis/v2/membership#Instructor

 and our tool can assume that the user is an instructor.

But, when a TA launches, we see 

http://purl.imsglobal.org/vocab/lis/v2/membership#Instructor,http://purl.imsglobal.org/vocab/lis/v2/membership/Instructor#TeachingAssistant

...if I check to see if the user is an instructor before I check to see if they are a TA, it will come back as instructor (which is bad).

Well, maybe I should check to see if a user is a TA first then?  Well, no, that doesn't work either.  If a user is a TA in one section but an Instructor in another section, we want them to come across as an instructor.

So, what are my options here?  Is there some other magical piece of data I should be looking at?  Can I set a flag in my tool json that tells it to only send the sub-role?  Hoping someone has some advice/guidance!

Chris