Cryptography suites should be required to define a well known context so that the resolution of the context property can be cached. If this is not done, then the context property can be defined in such a way that it behaves like a unique identifier controlled by the issuer in order to correlate the subject when the verifier resolves the @context JSON-LD document.
From the PING's review (https://github.com/w3cping/privacy-request/issues/120):
/cc @kdenhartog