Section 4 "Model" uses a non-robust Link detection algorithm which does not consider properties

[trwnh]

https://www.w3.org/TR/activitystreams-core/#model

A JSON object in the Activity Streams 2.0 document is a Link if either: (a) the object contains a type property whose value includes "Link" or (b) any of the types included in the value of the type property are defined as extensions of Link (see Mention for instance); otherwise the JSON object is considered an instance or extension of Object.

We should be able to infer that something is a Link if it has properties of a Link, mainly href. But as written above, the algorithm would declare the following to be an Object:

{
  "href": "https://example.com"
}

The algorithm described above also fails to account for logical inferencing, where the domain of href is specified to be Link.

I think that the paragraph here should be errata'd to add:

... or (c) the object contains a property whose domain is defined as "Link" (see href for instance)