Allow Form's "rel" to be a string or an array

[AndreMaz]

Current (01 October 2018) WoT spec defines Form's "rel" as a string that can take one of possible values: "readproperty", "writeproperty" , "observeproperty", "invokeaction", "subscribeevent" or "unsubscribeevent".

TD JSON Schema also specifies "rel" as string

"rel": {
   "type": "string"
}

One the other hand, the latest (12 September 2018) Protocol Binding Templates spec defines "rel" as an array.

{
    "href": "/example/light/currentswitch",
    "rel": ["readproperty", "writeproperty", "observeproperty"],
    "mediaType": "application/json"
}

Can you please sync the docs?

Suggestion, let "rel" be both (array or string) as does the OCF in their spec

        "rel": {
          "oneOf":[
            {
              "type": "array",
              "items": {
                  "type": "string",
                  "maxLength": 64
                },
              "minItems": 1,
              "default": ["hosts"]
            },
            {
              "type": "string",
              "maxLength": 64,
              "default": "hosts"
            }
          ],

[handrews]

If it helps, the next draft of JSON Hyper-Schema will also allow for either a string or array-of-strings value for rel (in the context of links rather than forms, though).

[mkovatsc]

The overall TD format allows "string or array-of-strings", as it is based on the JSON-LD format. So, yes, string or array-of-strings is the intended feature, and yes, we need to fix the TD spec.

[sebastiankb]

@AndreMaz Thanks for the hint.

@egekorkan This must also be fixed in the TD playground. Thanks

[egekorkan]

The new validation schema and the playground now support both string and array of strings

[sebastiankb]

@vcharpenay how can this reflected in ttl?

[sebastiankb]

op can be also an array

[sebastiankb]

please review

[mlagally]

In the discussion on Dec 21th we agreed that there should be a recommendation that the values of these fields "should be" consistent with the values of readonly, writeonly, ...

[vcharpenay]

op cannot be an arbitrary array, though. It is only valid for the following combinations:

• readproperty, writeproperty
• readproperty, observeproperty
• readproperty, writeproperty, observeproperty
• subscribeevent, unsubscribeevent

What about defining one op value for each combination instead of defining it as a "string or array of string"?

[takuki]

It is implemented in td-json-schema-validation.json as one or more of values permitted depending on which interaction affordance (or a Thing) the form belongs to. For example, the form in Property interaction affordance is defined as follows.

    "oneOf": [
        {
            "type": "string",
            "enum": [
                "readproperty",
                "writeproperty",
                "observeproperty",
                "unobserveproperty"
            ]
        },
        {
            "type": "array",
            "items": {
                "type": "string",
                "enum": [
                    "readproperty",
                    "writeproperty",
                    "observeproperty",
                    "unobserveproperty"
                ]
            }
        }
    ]