Re: IOTDB worldview vs EVRTHNG

Hi Vlad,

1)

No one's obliged to use it! One can do (e.g.) PATCH /light/1 { on: true }
or PATCH /hue/33 { powered: 1 }. But the possibility exists to introspect
and get more information _if you want to know that "on" and "powered" mean
the same thing for these two different devices.

2)

Isn't semantics a core mission of this WG, and hence JSON-LD is a must?

3)

I'll tediously mention again that I'm not bringing forward something
theoretical. If you run up the HomeStar project, you'll get an API that you
can just send JSON requests to and control a fair number of real world
things, or you can start introspecting the models and build interfaces. I
think we're far past the Hello World stage.

Here's two screenshots of working Web and App interfaces created entirely
through introspection
https://twitter.com/dpjanes/status/606106181409447936

I apologize for not have a working server up on the net to play with. I'm
about 48 hours into knowing W3C actively wants to do this.

D.


On Wed, Jun 3, 2015 at 9:26 AM, Vlad Trifa <vladounet@gmail.com> wrote:

> Yes, but that's exactly my point! It's not about the Web Thing who needs
> to understand JSON-LD: it's about any client that wants to interact with
> it! They shouldn't be obliged to use it.
>
> It's primordial to get sufficient information based on http/json only (by
> predefining a set of json data model with clear semantics) and not be
> obliged parse an additional json-ld just for this, because it's overkill in
> 96.4% of real-world use cases I've come across (it adds a layer of
> complexity upfront that I simply don't need for most of apps I can think
> of).
>
> If we want to make something that's useful, I'm voting for lowering the
> access barrier to get a "hello world" up & running. JSON-LD as a MUST would
> do the opposite.
>
> Whatever the IG comes with should be a simple & clean model (just
> http/json) that anyone can use easily for simple scenarios. What's
> important iis that tis simple model comes with well-thought extension
> points to support "advanced" features (such as MQTT/WebSockets mappings,
> JSON-LD, etc.). If we decide to bake all these features into the basic
> model as a "must", we're just raising the access barrier and you won't see
> me bet any money on the success of such a bloated "standard"...
>
>
>
> On 03 Jun 2015, at 14:06, David Janes <davidjanes@davidjanes.com> wrote:
>
> -- Just splitting this conversation, so we don't have to many concurrent
> threads! --
>
> JSON-LD
>
> There's no dependency on Things themselves actually understanding JSON-LD,
> just that there exists a Model that's written in JSON-LD that explains how
> to interact with that Thing.
>
> For example, back to the WeMo Socket. Here's the Model for this in our
> authoring language (JavaScript):
>
> https://github.com/dpjanes/homestar-wemo/blob/master/models/WeMoSocket.js
>
>
> Here's what it looks like in JSON-LD
>
> https://gist.github.com/dpjanes/79a256c02c0a31c9aa42
>
>
> What's great is that I can use introspection to create user interfaces for
> this, just based on the JSON-LD. But yeah, the WeMo itself doesn't know
> anything about JSON-LD. In fact, the protocol is some horrible UPnP XML
> stuff, but the end user doesn't need to know that.
>
> D.
>
>
>
>
> On Wed, Jun 3, 2015 at 8:48 AM, Vlad Trifa <vladounet@gmail.com> wrote:
>
>> Hey David,
>>
>> I partially agree with this.
>>
>> I'll rarely need to get the metadata of what properties & co are, so they
>> obviously shouldn't be returned every time, and that's why you'd call the
>> end-point below only once (to discover it and understand it). Then you'll
>> only need to interact with ".../sensors/humidity" directly where you don't
>> get that data model anymore - but just the definition.
>>
>> I'm not OK with the idea that any property and sensor MUST use JSON-LD.
>> If we can all agree here on one basic model that is good enough and
>> sufficiently flexible to deal with (yes, you are introducing some coupling,
>> which you're doing with JSON-LD anyway, and even more so), then I don't
>> need JSON-LD.
>>
>> But I'm obviously OK with the idea that any device can (and even should)
>> expose its services with json-id so that it has more flexibility to expose
>> metadata & co and more (non-wot) clients can also process it.
>>
>>
>> Now, where I disagree is the "actions" model is RPC and non-RESTful. This
>> is most likely because I didn't explain them well, so let's see:
>>
>> Doing a PUT .../actions/lockdoor is indeed non-RESTful (or worse: GET
>> .../actions/lockdoor?lock=true ---> horrible, I know!!), because you're
>> putting rpc semantics in the URL. That's bad!
>>
>> BUT, this is *not* how actions work!
>>
>> When you do an action, you're creating a REST resource (so you MUST use
>> POST), and this resource is a "request to do something" (that might happen
>> or not).
>>
>> The way you'd unlock the door would look like this:
>>
>> POST http://mydoorlock.com/lock29/actions/changestatus
>> {
>> "status":"lock"
>> }
>>
>> 202 ACCEPTED  (or 201 CREATED, if instantaneous)
>> Location: http://mydoorlock.com/lock29/actions/changestatus/66373
>>
>> Then you can retrieve this resource any later time and see whether it's
>> been successfully executed or not. This has the added advantage that you
>> naturally have a buffer where different clients can schedule several
>> requests simultaneously (and the device decides when & how to schedule
>> those), which is particularly helpful, clean, and RESTful.
>>
>> I'll happily sit down and watch you demonstrate what's not RESTful about
>> this ;)
>>
>> What do you think?
>>
>>
>> Vlad
>>
>>
>>
>> On 03 Jun 2015, at 00:50, David Janes <davidjanes@davidjanes.com> wrote:
>>
>> So just taking these as examples (make sure to add Accept:
>> application/json)
>>
>> http://devices.webofthings.io/pi/sensors/
>>
>>   "humidity": {
>>
>>     "description": "A temperature sensor.",
>>
>>     "frequency": 5000,
>>
>>     "name": "Humidity Sensor",
>>
>>     "timestamp": "2015-06-02T16:06:26.398Z",
>>
>>     "type": "float",
>>
>>     "unit": "percent",
>>
>>     "value": 40.2
>>
>>   },
>>
>> From IOTDB's POV, there's a bunch of stuff being mixed together here:
>>
>> The model, comprising the values: description, type, unit
>> The metadata, comprising the value: name, frequency
>> The ostate, comprising: timestamp, value
>>
>> In IOTDB world, the value record would look something like this:
>>
>> {
>>  "@context": "...",
>>  "value": 40.2,
>>  "timestamp": "2015-06-02T16:06:26.398Z",
>> }
>>
>> @context is JSON-LD magic to provide meaning to "value" and "timestamp",
>> defined in the Model (@vocab may be needed too, JSON-LD needs some
>> tightening).
>>
>> The Model is then basically static, and the part that defines value e.g.
>> looks like this
>>
>> {
>>  "@id": "#value",
>>  "iot:unit": "iot:float",
>>  "iot:purpose": "iot-attribute:sensor.humidity",
>> }
>>
>> A lot of those iot: can be taken out, but you get used to it.
>>
>> Metadata is less frequently changing data and is to taste, but you'll
>> note that the value will only reference the Model, not the Metadata.
>> Furthermore, Metadata will typically draw it's definitions from the core
>> vocab, rather than having to be defined on a case by case basis.
>>
>>
>> D.
>>
>>
>>
>>
>>
>
>