The set of types we will accept as activities.

There’s an explicit set of allowed activity types.

The URI of the context of an ActivityStreams object is expected to be this literal string.

NOTE THAT the URI actually used in the published suite of activitystreams-test-documents use this URI with ‘http’ rather than ‘https’ as the property part, but the spec itself specifies ‘https’.

The set of types we will accept as actors.

There’s an explicit set of allowed actor types.

The Clojure reader barfs on :@context, although it is in principle a valid keyword. So we’ll make it once, here, to make the code more performant and easier to read.

These types are not explicitly listed in Section 3.3 of the spec, but are mentioned in narrative

The set of object types we will accept as nouns.

There’s an explicit set of allowed ‘object types’, but by implication it is not exhaustive.

A regex which tests conformity to RFC 5646. Cribbed from https://newbedev.com/regex-to-detect-locales

Severity of faults found, as follows:

1. :info not actually a fault, but an issue noted during validation;
2. :minor things which I consider to be faults, but which don’t actually breach the spec;
3. :should instances where the spec says something SHOULD be done, which isn’t;
4. :must instances where the spec says something MUST be done, which isn’t;
5. :critical instances where I believe the fault means that the object cannot be meaningfully processed.

Hack for implementing a severity hierarchy

The URI of the context of a validation fault report object shall be this literal string.