Here is my formatted message:

I think there might be an inconsistency between application/linkset and application/linkset+json

The link header serialization says "The rel parameter can, however, contain multiple link relation types." https://tools.ietf.org/html/rfc8288#section-3.3

However, in the JSON serialization you define, it appears that it can only support a single link relation type.

Unless you mean for user agents to:

a. deduplicate links that share a common context and target but a different rel
b. interpret the object property name as a space-delimited set of relation types

If either of those is the case, I think it would be good to explicitly give that example.

OTOH, I think I would prefer if your link object replaced the rel as object property name with the constant, target, and make rel a sibling of href, permitting it to be an array

Could it be that you are reacting to version 3 of the Internet Draft, and not version 4 that was released today? See https://tools.ietf.org/html/draft-wilde-linkset-04

@hvdsomp, I followed @dret's tweet directly to version 4.

Here is the line in question: https://github.com/dret/I-D/blob/master/linkset/draft-wilde-linkset-04.txt#L351

Specifically:

For each distinct relation type that the link context has with link targets, a link context object MUST have an additional member. ... The name of this member expresses the relation type of the link as follows:

• ... the name of this member is the registered name of the relation type.

Consequently, a link context object can have one ore more link target objects but those links can only have a single relation type.

The example also makes this clear:

   {
     "linkset":
       [
         { "anchor":"http://example.net/bar",
           "item": [
                 {"href": "http://example.com/foo1"},
                 {"href": "http://example.com/foo2"}
           ]
         }
       ]
   }

Which we can reformat into a link header as:

Link: <http://example.com/foo1>; rel="item" anchor="http://example.net/bar" ,
  <http://example.com/foo1>; rel="item" anchor="http://example.net/bar"

However, how would one serialize this link header back into JSON?

Link: <http://example.com/foo1>; rel="item http://example.net/relation/other1" anchor="http://example.net/bar",
  <http://example.com/foo2>; rel="item http://example.net/relation/other2" anchor="http://example.net/bar"

It's not clear in the current draft (v4). There is an example of a link header with multiple link relation types in RFC 8288 (search for http://example.net/relation/other).

What I proposed at the end of my message would look like this:

   {
     "linkset":
       [
         { "anchor":"http://example.net/bar",
           "target": [
                 {"href": "http://example.com/foo1",
                  "rel": ["item", "http://example.net/relation/other1"]},
                 {"href": "http://example.com/foo2",
                  "rel": ["item", "http://example.net/relation/other2"]}
           ]
         }
       ]
   }