When I first configured our Turnitin LTI tool, I followed the guidance in this document:
This document lists 5 custom parameters that can be passed through from Canvas to Turnitin, along with 5 corresponding LTI Variable substitutions that allow values from the Canvas assignment to be passed into Turnitin:
From knowledge of the Turnitin LTI API, I knew there were many other settings for TII assignments that could be included in the LTI configuration. But for some reason, it seemed really hard to find them.
Turnitin were able to provide me a link to much fuller documentation for their LTI:
(see specifically section "Custom resource settings that can be defined")
And this very useful Canvas documentation gives details of all of the variable substitutions that Canvas allows in LTI configurations:
With these 2 documents, it's possible to fully specify what settings Turnitin assignments should have.
Note that all TII settings that you set in this way will not be editable via TII Settings page within the Canvas interface.
This has enabled us to create an External Tool with fully locked down behaviour, to ensure that all assignments are treated the same way in Turnitin and hence providing consistency for students.
I hope this is useful for other Admins!
NOTE from 10 September 2020: I was browsing this article for a question I had today and found that the Turnitin document giving the full list of the parameters had changed location. So I have updated the URL.