All CIS-Standards, except CIS-4, require CIS-0. CIS-0 defines the supports function, that enables a smart contract to state which standard it supports.
How is a CIS-4 contract supposed to communicate the fact that it is a CIS-4 contract? This standard does not require CIS-0 and does not define the supports function itself.
Hi there
Whether CIS-0 should be mandated by each standard could be an interesting discussion.
Since it is currently not mandated, a contract may still implement it if they wish to be discoverable.
So to answer the question: if a contract wants to communicate this is an implementation of CIS-4, they would also implement CIS-0 and use the Standard identifier defined as part of CIS-4.
We do this in our example for CIS-4 as well.