Proposal: use TD `default` values

[derwehr]

hello, I'd like to propose the scripting API to define variables the consumer leaves undefined with the default values from the TD (or const values?).

A simple use-case would be a Thing, expecting a fixed payload parameter based on the Interaction Affordance, like in the TD below.

Now with the scripting API using the default values a user won't have to worry about knowing the correct commandId.

{
  "actions": {
    "move": {
      "type": "object",
      "properties": {
        "commandId": {
          "type": "integer",
          "default": 5
        },
        // other dynamic properties like coordinates
      }
    },
    "dimLight": {
      "type": "object",
      "properties": {
        "commandId": {
          "type": "integer",
          "default": 6
        }
        // other dynamic properties like time span
      }
    }
  }
}

[danielpeintner]

Are you referring to the Consumed or Exposed side?

e.g., on ExposedThing side Do you mean that a Scripting API implementation needs to look into the DataSchema and detect whether it has default or const and report it accordingly without adding a handler?

[derwehr]

On the ExposedThing side. If I understand it correctly, then a TD already describes this case perfectly and there should not be a need for adding handlers.

[relu91]

Call 29/01:

• @zolkis from the ExposeThing side is saving 1 line of JS, but there might be even more use case for different automation needs. Is it really worth it?
• @danielpeintner agrees, I see the use case but it is not that much work. Plus it adds complexity to the implementation (you need a full jsonschema parser)
• @relu91 even from the Consumer side could be added but it is still not that much different.

[derwehr]

Thank you for discussing my proposal :) My understanding of the WoT is that when adding new devices to a WoT application or exchanging existing ones, ideally, you'd only need to consume a TD and should not need to modify any code. Therefore, I'm trying to describe everything in the TD and to avoid adding handlers. Would my proposal to improve this 'out of the box TD compatibility' be a better fit for other WoT specifications like the protocol bindings, or is this something every developer would decide upon independently?