Current State

All tags are propagated 'downstream' (i.e. from input to output). This seems likely to be an unnecessary restriction and may not model all use cases.

Future work

Explore use cases for 'back tags' (i.e. tags that propagated from output to input) and implement them.
Possible use cases:

• propagating requirements via checks
• propagating authenticity requirements (e.g. requirements that data be associated with a user action)