reusing Vocabulary terms in Social API (Hypermedia)

Hello,

Since we start clarifying our direction in Social API, I would like to
discuss leveraging *terms* which we find in existing vocabularies and
new one's which we work on.

First I will make short detour. In Architecture of the World Wide Web,
Volume One we find:

    Good practice: URI opacity

    Agents making use of URIs SHOULD NOT attempt to infer properties
    of the referenced resource.

http://www.w3.org/TR/webarch/#uri-opacity

In context of our work I would interpret it as:
"Since URIs should stay opaque, we SHOULD NOT mandate what to include in
URIs denoting resource in API - no *magic* paths!"

If someone wants to expose all the resources using URIs like

* https://example.com/c251a9aa-bf89-466f-a8d5-a18ea5377f70
* https://example.com/18d96e54-cfb6-4d14-bef0-80addf21e7a2
* https://example.com/58438e23-fe45-4589-8ecb-43a459da075a

Everything should still work :)


How do we find then things like: *list of elf's friends*?

HYPERMEDIA to the rescue \o/

Many people feel quite comfortable with *link relations*. When someone
publishes and article with multiple pages. This person doesn't need to
follow conventions like: "For second page add /2 to your URL" etc.
Once we fetch (dereference) given web page, we can simple search for
links with rel="next" or rel="prev" leaving publisher freedom to use
whatever they want in their URLs.
One can find many more such link relations on microformats wiki,
referenced in official HTML5 spec!
http://microformats.org/wiki/existing-rel-values

In similar way everyone could find list of my friends. Once someone
fetches (dereferences) my online profile, could search in it for links
with rel="knows" or rel="follows". Actually RDFa reuses rel attribute
and we can also use similar pattern in JSON-LD or turtle.
(we can find relation/property/predicate *knows* in FOAF or schema.org!)

Since I know few thousands of people, and other people find themselves
followed online even by millions of other people. We need a way to avoid
publishing all those links directly on our homepage! One of the proposed
solutions comes from Hydra CG -
https://www.w3.org/community/hydra/wiki/Collection_Design

{
  "@context": {
    "@vocab": "http://schema.org",
    "hydra": "http://www.w3.org/ns/hydra/core#"
  },
  "@id": "https://wwelves.org/perpetual-tripper",
  "name": "elf Pavlik",
  "hydra:collection": [
    {
      "@id": "https://wwelves.org/perpetual-tripper/friends",
      "name": "elf Pavlik's friends",
      "hydra:manages": {
        "property": "knows",
        "subject": "https://wwelves.org/perpetual-tripper/friends"
      }
    },
    {
      "@id": "https://wwelves.org/perpetual-tripper/events",
      "name": "elf Pavlik's events",
      "hydra:manages": {
        "property": "attendee",
        "object": "https://wwelves.org/perpetual-tripper/friends"
      }
    }
  ]
}

Even that I chose to use vanity URLs ending with /friends or /events, I
could as well use generic /c251a9aa-bf89-466f-a8d5-a18ea5377f70 and it
will still work. If you read this example carefully you would notice
that I even used attendee relation/property/predicate in *inverse*
direction :)

I will leave it here and I hope we can discuss together various
advantages, and possible drawbacks of such approach...

Cheers :)