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Michael Koster edited this page Jan 22, 2016 · 40 revisions

Resources used in the demo and instructions for setup and self-test

Live Demo instance of a light thing with a discovery index. Read only please.

http://104.131.134.13:8000/

The content formats used are application/link-format+json, application/senml+json (draft-01) and application/collection+senml+json.

link-format+json is used for link operations and senml+json is used for data items and form items. collection+senl+json is for constructing or inspecting items and links together as a collection.

An index has only links but allows adding links with POST and modifying links with PATCH according to:

https://datatracker.ietf.org/doc/draft-ietf-core-resource-directory/

For example, you can do: GET http://104.131.134.13:8000/index?rt=thing (accept: application/link-format+json) and get a link to a thing:

[{"rt": ["light", "thing"], "href": "/light/"}]

Then you can use the relative reference returned to construct the URL for the next step"

GET http://104.131.134.13:8000/light/ (accept: application/link-format+json) and get links to its (subresource) capabilities:

[ { "href": "", "rel": [ "self" ] }, { "rt": [ "capability", "onoff" ], "href": "onOff", "rel": "sub" }, { "rt": [ "capability", "colorhs" ], "href": "colorHS", "rel": "sub" }, { "rt": [ "capability", "brightness" ], "href": "brightness", "rel": "sub" } ]

Then we can GET http://104.131.134.13:8000/light/onOff/ (accept: application/link-format+json) and receive the following representation which contains links to property subresources and a link which points to a form. The link describes it as a ["form" "item"] {"rt": ["action", "change"], "href": "change", "rel": ["form", "item"]} that can ["change" "action"] the context resource which is type onoff (self link should have the rt=onoff attrval)

[{"href": "", "rel": ["self"]}, {"rt": ["action", "change"], "href": "change", "rel": ["form", "item"]}, {"rt": ["property", "currentstate"], "href": "currentState", "rel": "sub"}, {"rt": ["property", "targetstate"], "href": "targetState", "rel": "sub"}, {"rt": ["property", "delaytime"], "href": "delayTime", "rel": "sub"}]

If you use the schema, you might know ahead of time that you are looking for a "change" ;-) so you could just ask for it: GET http://104.131.134.13:8000/light/onOff/?rt=change and just get the link you are seeking:

[{"rt": ["action", "change"], "href": "change", "rel": ["form", "item"]}]

So then you GET the form (in SenML content type for now...): GET http://104.131.134.13:8000/light/onOff/change (accept: application/senml+json)

{"bn": "/light/onOff/", "e": [{"fv": {"rel": "action", "href": "actuation", "template": [], "type": ["change", "action"], "method": "POST", "ct": "application/collection+senml+json"}, "n": "change"}]}

The form item retrieved describes how to change onoff; which is by performing a method=POST to the resource at href=actuation constructed according to a template (TBD) using the content format ct=application/collection+senml+json

Here is the entire "onOff" resource representation with links and items in collection format.

{"bn": "/light/onOff/", "e": [{"fv": {"rel": "action", "href": "actuation", "template": [], "type": ["change", "action"], "method": "POST", "ct": "application/collection+senml+json"}, "n": "change"}], "l": [{"href": "", "rel": ["self"]}, {"rt": ["action", "change"], "href": "change", "rel": ["form", "item"]}, {"rt": ["property", "currentstate"], "href": "currentState", "rel": "sub"}, {"rt": ["property", "targetstate"], "href": "targetState", "rel": "sub"}, {"rt": ["property", "delaytime"], "href": "delayTime", "rel": "sub"}]}

There is a meta-catalog example at thingschema.org that has an entry pointing to this index to bootstrap the discovery:

{
  "href": "http://104.131.134.13:8000/index",
  "rt": "index",
  "ct": ["application/link-format+json", "application/collection+senml+json"]
  "comment": "hypermedia demonstrator discovery"
}

Machine Hypermedia Toolkit

The toolkit is written in python and is Apache 2 licenced. It can be downloaded from the github repository at:

[Machine Hypermedia Toolkit source repository and installation instructions] (https://github.com/connectIOT/MachineHypermediaToolkit)

Public resource at thingschema.org

There is a public resource for hosting the schema and JSON-LD context files. thingschema.org

The content of thingschema.org is stored at a github repository: thingschema-content

thingschema.org serves a standard JSON-LD context file that can be used by including "@context": "http://thingschema.org" in your JSON-LD file

In addition there is a WoT interaction model schema and a domain-specific schema for lighting.

In the examples directory there is a model for an instance of a light, and a meta-catalog file with pointers to other resources like IETF Resource Directories, W3C WoT Thingdescriptions, hypercats, or other discovery resources.

Context file: http://thingschema.org/context.jsonld

W3C Interaction Model : http://thingschema.org/wot.jsonld

Lighting domain model: http://thingschema.org/light.jsonld

Meta-catalog: http://thingschema.org/examples/catalogs.jsonld

Example light model: http://thingschema.org/examples/lightmodel.jsonld

Example IPSO Smart Object constructor: http://thingschema.org/examples/IPSO-rm.json

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