Sound reasoning with unknown dialects
It must be possible in some practical circumstances for systems reasoning with rulesets to soundly proceed with parts of their work even when a ruleset contains rules which use extensions not known to the system implementors.
Position in the DC structure
Level: Requirement [PROPOSED]
To give room for partial interoperability, and evolution of dialects.
Also, this may be a good way to look at extension layering and re-use.
Of course some rulesets will not support reasoning with only partial understanding. With a monotonic ruleset, it's pretty simple to just ignore the rules using features you don't understand. Do non-mon rulesets simply need to be flagged as non-mon an exempted from this requirement?