JSON Siren vs. HAL Representations

hal.json

{
  "_links": {
    "self": { "href": "/orders" },
    "next": { "href": "/orders?page=2" },
    "find": { "href": "/orders{?id}", "templated": true }
  },
  "_embedded": {
    "orders": [{
        "_links": {
          "self": { "href": "/orders/123" },
          "basket": { "href": "/baskets/98712" },
          "customer": { "href": "/customers/7809" }
        },
        "total": 30.00,
        "currency": "USD",
        "status": "shipped",
      },{
        "_links": {
          "self": { "href": "/orders/124" },
          "basket": { "href": "/baskets/97213" },
          "customer": { "href": "/customers/12369" }
        },
        "total": 20.00,
        "currency": "USD",
        "status": "processing"
    }]
  },
  "currentlyProcessing": 14,
  "shippedToday": 20
}

siren.json

{
  "class": "orders",
  "properties": {
    "currentlyProcessing": 14,
    "shippedToday": 20
  },
  "entities": [
    {
      "class": "order list-item",
      "rel": "order",
      "properties": {
        "total": 30.00,
        "currency": "USD",
        "status": "shipped"
      },
      "entities": [
        { "rel": "basket", "href": "/baskets/98712" },
        { "rel": "customer", "href": "/customers/7809" }
      ],
      "links": [{ "rel": "self", "href": "/orders/123" }]
    },
    {
      "class": "order list-item",
      "rel": "order",
      "properties": {
        "total": 20.00,
        "currency": "USD",
        "status": "processing"
      },
      "entities": [
        { "rel": "basket", "href": "/baskets/98713" },
        { "rel": "customer", "href": "/customers/12369" }
      ],
      "links": [{ "rel": "self", "href": "/orders/124" }]
    }
  ],
  "actions": [{
      "class": "find-order",
      "href": "/orders",
      "fields": [{ "name": "id", "type": "number" }]
  }],
  "links": [
    { "rel": "self", "href": "/orders" },
    { "rel": "next", "href": "/orders?page=2" }
  ]
}

Is a "class" a string as in provide example or must be an array as in spec (spec says "MUST") ? [or can be either but spec needs to not say MUST]
Same question for rels.
Many thanks.

A minor issue with the HAL resource is that it is not valid JSON because of this comma at the line end (the draft has the same issue)

@cappelaere, it looks like this was created one month before @kevinswiber moved class and rel to be arrays so it's likely an out of date aspect of this gist. kevinswiber/siren@9972c84

In my opinion HAL is the most straightforward... well apart from the _embeded concept which can become cumbersome sometimes. So I like HAL - _embeded !

The SIREN representation doesn't seem equivalent to the HAL one. The HAL representation has an embedded representation called "orders" which is an array of orders. The SIREN representation has two embedded resources, unfortunately unnamed, which are order list-item.

Anyone know which json standard has become most popular? I'm writing a bunch of json schema for various multimedia apps but standardization among units is lacking. Will probably go with something closer to Siren.

You may find this useful and/or interesting: http://json-schema.org/latest/json-schema-core.html