Using an extension vs. using an external vocabulary in section 5 "Extensibility"

[evanp]

We don't differentiate between using an existing vocabulary like schema.org and vcard, and an extension like FEP 4ccd, designed specifically for Activity Streams use.

Is there such a difference?

[cristianolongoodhl]

I can't recognize any difference.

[trwnh]

I don't think the difference is between schema.org vs FEPs. I think it's more like this:

• Extensions: By default, AS2 documents include the AS2 context; you can extend that context with additional term definitions.
• External vocabulary: Most AS2 terms are defined by AS2-Vocab and included in the activitystreams namespace; some terms in the AS2 context are not from the activitystreams namespace.

So for example:

• vcard: as a prefix IS representing an external vocabulary but IS NOT an extension.
• ldp:inbox as a property IS from an external vocabulary but IS NOT an extension.
• as:sensitive as a property IS NOT from an external vocabulary but IS an extension.
  • If/when as:sensitive gets formally adopted/grandfathered, then we would say it IS NOT an extension.

Extensions make sense when talking about the default context, and external vocabularies make sense when talking about namespaces or specifications.