FRETish application to non-functional requirements

[cwlhobbs]

I have been reading the FRET(ish) documentation and find that the FRETish language seems to be oriented towards functional requirements (the system SHALL do X within Y ms of Z happening). Is it also useful for non-functional requirements?

My particular interest is in its usefulness for expressing Assurance Requirements of a complex system: requirements covering the transparency, verifiability, auditability, accountability, access for independent scrutiny and security of a system being developed.

Perhaps the difference is between placing requirements on a product and placing requirements on the development process to create the product: e.g., "All source code SHALL be available for independent inspection", with the implied "...and exactly what is available for inspection is what is going into the product --- no one can change it en route to the product".

Is FRETish able to handle this type of requirement?