Copyright © 2020-2021 W3C ® ( MIT , ERCIM , Keio , Beihang ). W3C liability , trademark and permissive document license rules apply.
The WoT Profile Specification defines a Profiling Mechanism and a WoT Core Profile , which enables out of the box interoperability among things and devices. Out of the box interoperability implies, that devices can be integrated into various application scenarios without deep level adaptations. Typically only minor configuration operations are necessary (such as entering a network key, or IP address) to use the device in a certain scenario. These actions can be done by anyone without specific training.
The WoT Core Profile defines a set of constraints and rules , which compliant thing descriptions have to adopt to guarantee interoperability.
These rules are prescriptive, to ensure that compliant implementations satisfy the semantic guarantees implied by them. We call this set of rules a Profile .
The WoT Profile Specification as defined in this document serves two purposes:
This document incudes a binding of the core data model to HTTP(S) and selected notification sub-protocols. The core data model can be bound to other protocols - it is expected that bindings to other protocols (e.g. MQTT, CoAP) will be defined in the near future.
A TD that is compliant to the core profile MUST adhere to both the constraints on the data model and the protocol binding.
Devices that constrain their use of the Thing Description to the WoT Core Profile can interoperate with each other out-of-the-box.
Note that the core profile is not exclusive. Device implementers are free to adopt other features of the thing description that go beyond the constraints of the core profile, however the interoperability guarantees of the core profile hold only for the WoT Core Profile subset.
The W3C WoT Thing Architecture [ wot-architecture ] and WoT Thing Description [ wot-thing-description ] define a powerful description mechanism and a format to describe myriads of very different devices, which may be connected over various protocols. The format is very flexible and open and puts very few normative requirements on devices that implement it.
However, this flexibility de-facto prevents interoperability, since, without additional rules , it allows implementers to make many choices that do not provide guarantees of common behavior between implementations.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
This document was published by the Web of Things Working Group as an Editor's Draft.
Comments regarding this document are welcome. Please send them to public-wot-wg@w3.org ( subscribe , archives ).
Publication as an Editor's Draft does not imply endorsement by the W3C Membership.
This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 1 August 2017 W3C Patent Policy . W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy .
This document is governed by the 15 September 2020 W3C Process Document .
The W3C WoT Architecture [ wot-architecture ] and the WoT Thing Description [ wot-thing-description ] have been developed as a versatile format, that allows describing the interactions between multiple devices and protocols.
This flexibility permits an easy integration of new device types and protocols, however it risks interoperability, since there are no guarantees that two devices which are formally spec-compliant, will be able to communicate.
To increase adoption of the WoT specifications, interoperability between on premise devices, edge devices and the cloud is essential. Even if every manufacturer is implementing the current Thing Description specification in full flexibility, there is no interoperability guarantee; many choices are still left to the implementations and there are very few normative requirements that a device has to fulfill.
A Thing Description can be used in two fundamentally different deployment scenarios:
For green field deployments, where the implementations are being carried out and corresponding thing descriptions are being created, it is easier to achieve full interoperability by using a small, extensible Core Profile .
In the brown field area, due to the nature of existing deployments and protocols, a broad spectrum of variations and potentially high complexity of thing descriptions inhibits interoperability and will most likely lead to additional profiles of the WoT Thing Description and domain-specific thing consumer implementations.
The WoT Core Profile can be used by green field deployments and gives guidance to new implementers of the WoT specifications. It has already proved in brown-field scenarios in the PlugFests, where existing devices, that already existed as products, prototypes or demonstrators, were described with Thing Descriptions that are constrained to the Core Profile .
During the recent WoT PlugFests there were many de-facto agreements on the use of a small constrained subset of interaction patterns and protocol choices. These de-facto agreements select a common subset of the WoT Thing Description , based on proven interoperability among manufacturers.
The aim of this specification is to formalize these agreements by defining a WoT Core Profile based on the choices that were made by the implementers of PlugFest devices.
The WoT Core Profile contains additional normative requirements that MUST be satisfied by devices to be compliant to the profile.
Adoption of the WoT Core Profile will significantly limit the implementation burden of device and cloud implementors.
The WoT Core Profile was defined with the following main goals:
It makes choices on the required metadata fields as well as the supported interactions and protocol endpoints. It introduces some constraints on data schemas for properties and actions which are required for resource constrained devices in real-world deployments. The format does not forbid the use of additional elements of the WoT Thing Description for vendor specific extensions, however this will impact interoperability.
Devices, which implement the Core Profile , are out-of-the-box interoperable with other Core Profile compliant devices. Furthermore, the Core Profile simplifies device validation and compliance testing since a corresponding conformance test suite can be defined.
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY , MUST , MUST NOT , NOT RECOMMENDED , RECOMMENDED , and SHOULD in this document are to be interpreted as described in BCP 14 [ RFC2119 ] [ RFC8174 ] when, and only when, they appear in all capitals, as shown here.
A device or consumer implementation complies with this specification if it follows the normative statements in the present document.
A JSON Schema [ JSON-SCHEMA ] to validate the compliance of a Thing Description with the core profile is provided in Appendix § 5.5 JSON Schema of the Core Profile .
This specification uses the same terminology as the WoT Architecture and Thing Description specifications.
For convenience of the reader, we use the terms keyword and field for the linguistic notion vocabulary term as defined in the Thing Description Specification.
We use the terms device and thing in an interchangeable manner.
In order to conform with a profile, a Web Thing MUST conform with all the normative statements in the profile's specification.
In
order
to
denote
that
a
given
Web
Thing
conforms
to
one
or
more
profiles,
its
Thing
Description
MUST
include
a
profile
member
[
wot-thing-description
].
The
value
of
the
profile
member
MUST
be
set
to
either
a
valid
URI
[
RFC3986
]
identifying
a
single
profile,
or
an
array
of
valid
URIs
identifying
multiple
profiles.
{
"@context": "https://www.w3.org/2019/wot/td/v1",
"id": "urn:dev:ops:32473-WoTLamp-1234",
"profile": "https://www.w3.org/2021/wot/profile/core",
"title": "My Lamp",
"description": "A web connected lamp",
...
}
{
"@context": "https://www.w3.org/2019/wot/td/v1",
"id": "urn:dev:ops:32473-WoTLamp-1234",
"profile": [
"https://www.w3.org/2021/wot/profile/core",
"https://www.w3.org/2021/wot/profile/constrained"
],
"title": "My Lamp",
"description": "A web connected lamp",
...
}
The core data model incorporates the data model defined by chapter 5 of the Thing Description specification. The normative rules defined by that data model are the baseline for the definition of the core data model and are normative for the core data model. A core profile compliant implementation MUST additionally satisfy the requirements of this chapter.
The following rules are applicable to multiple classes of the WoT Thing Description Specification, as they provide clearer semantics, improved readability and simplified processing on resource constrained devices.
One of the primary benefits of the WoT Thing Description over a typical IoT format is the additional documentation for a human reader.
Therefore,
the
fields
title
and
description
are
MANDATORY
for
Things,
Property
Affordances,
Action
Affordances,
Event
Affordances
and
Data
Schemas.
It is possible to have empty values for these fields, if, for specific purposes it is not desired to provide documentation, however this is NOT RECOMMENDED and the conscious decision is obvious from the TD.
The
length
of
id
,
description
and
descriptions
values
is
limited
to
512
characters.
The
length
of
title
and
titles
values
is
limited
to
64
characters.
Where
a
type
permits
using
an
array
of
string
or
a
string
,
an
array
of
string
MUST
be
used.
TODO: decide if multiple types and contexts are required.
In this case the following section could be added:
The
only
exception
to
this
rule
are
@context
and
@type
annotations,
where
both
string
or
array
of
string
MAY
be
used.
Where
a
type
permits
using
an
array
of
DataSchema
or
a
DataSchema
,
an
array
of
DataSchema
MUST
be
used.
All
elements
of
an
enum
MUST
be
either
string
or
number
.
Different
types
in
a
single
enum
are
NOT
PERMITTED.
To provide minimum interoperability, the following metadata fields of a Thing MUST be contained in a compliant Thing Description:
| keyword | type | remarks |
|---|---|---|
| title | string | human readable documentation |
| id | urn_type | a globally unique urn of the thing |
| description | string | human readable documentation |
| created | date | human readable documentation |
| modified | date | human readable documentation |
| support | urn_type | human readable documentation |
| security | array of string | simplified handling |
| version | VersionInfo | clear versioning, easy to compare different TDs |
It is RECOMMENDED to use the value "" for strings, where the value cannot be determined.
If a Thing Description is used solely within a company, the email address of the developer SHOULD be used in the support field, if the Thing Description is provided externally, a support email address SHOULD be used.
It will be evaluated whether the profile also recommends some new TD terms that may be introduced in TD 1.1. Currently the following terms are discussed: serialNumber, hardwareRevision, softwareRevision, loc_latitude, loc_longitude loc_altitude, loc_height, and loc_depth. If these, or some of them, are defined in the TD 1.1 model, they may be recommended here in one of the next draft updates.
Data Schemas are used for the values of Properties, Action input and output parameters and Event message payloads. The value of a Data Schema can be a simple type (boolean, integer, number, string) or an instance of a structured type (array and object).
The Core Data Model applies the following constraints and rules to the
DataSchema
class
of
section
5.3.2.1
of
the
WoT
Thing
Description
Specification.
This
section
defines
a
subset
of
the
class
DataSchema
that
can
be
processed
on
resource-constrained
devices.
The
Core
Data
Model
restricts
the
use
of
arrays
and
objects
to
the
top
level
of
Data
Schemas,
i.e.
only
a
one-level
hierarchy
is
permitted.
The
members
of
a
top
level
object
or
array
MUST
NOT
be
array
or
object
types.
This may appear as a severe limitation, however it is motivated by integrating with multiple cloud services. Many enterprise services and applications are based on (relational) databases, where individual property values are stored. Of course databases can also store objects (e.g. encoded as a JSON string), however this will prevent processing by other enterprise applications.
If a property conceptually has a deeper structure, such as grid of lamps with RGB colors, the structure can be represented in the keyword of the property, i.e. lamp1_color_r, lamp1_color_g and lamp1_color_b. A similar mapping can be done for arrays and hierarchical objects. This constraint leads to simpler Thing Descriptions that can be handled by very limited devices.
The following fields MUST be contained in a DataSchema:
| keyword | type | constraints |
|---|---|---|
| description | human readable description | |
| type | string | one of boolean, integer, number, string, array or object |
The
values
object
,
array
MAY
only
be
used
at
the
top
level
of
a
Data
Schema.
The
type
value
MUST
NOT
be
null
.
PropertyAffordance
class
of
section
5.3.1.3
of
the
WoT
Thing
Description
Specification.
The
following
property
fields
MUST
be
contained
in
the
properties
element
of
a
Profile
compliant
TD
:
| keyword | type | constraints |
|---|---|---|
| title | string | unique name among all properties |
| description | string | human readable description |
| type | string |
one
of
boolean
,
string
,
number
,
integer
,
object
or
array
.
The
type
value
null
MUST
NOT
be
used.
|
The
Thing
Description
permits
arbitrary
object
depths
for
properties.
Parsing
of
a
deeply
nested
structure
is
not
possible
on
resource
constrained
devices.
Therefore
each
property
MUST
NOT
exceed
a
maximum
depth
of
5
levels
of
nested
array
or
object
elements.
It
is
RECOMMENDED
to
keep
the
nesting
of
these
elements
below
4.
The following additional constraints MUST be applied to the Property Affordances of a Thing Description conforming to the Core Profile :
| keyword | type | constraint |
|---|---|---|
| const | anyType | MUST NOT be used |
| enum | array of simple type | Values of enums MAY only be simple types. Handling of any type is too complex to implement on resource constrained devices |
| forms | array of Forms |
The
Array
of
Form
of
each
property
MUST
contain
only
a
single
endpoint
for
each
operation
readproperty
,
writeproperty
,
observeproperty
,
unobserveproperty
.
|
| format | string |
If
the
field
format
is
used,
only
formats
defined
in
section
7.3.1-7.3.6
of
[
JSON-SCHEMA
]
MAY
be
used.
|
| oneOf | string |
The
DataSchema
field
oneOf
does
not
make
sense
for
properties
and
MUST
NOT
be
used.
|
| uriVariables | Map of DataSchema |
uriVariables
MUST
NOT
be
used.
|
It
is
highly
RECOMMENDED
to
always
specify
a
unit
,
if
a
value
has
a
metric.
Authors
of
Thing
Descriptions
should
be
aware,
that
units
that
are
common
in
their
geographic
region
are
not
globally
applicable
and
may
lead
to
misinterpretation
with
drastic
consequences.
The
field
unit
could
be
used
for
non-decimal
numeric
types
as
well,
e.g.
a
string
value
with
binary
or
hex
data
(
0xCAFEBABE
,
0b01000010
),
where
the
unit
is
hex
or
bin
,
to
indicate
how
the
value
should
be
interpreted.
It
is
strongly
RECOMMENDED
to
use
the
values
hex
,
oct
or
bin
in
this
case
to
achieve
interoperability.
ActionAffordance
class
of
section
5.3.1.4
of
the
WoT
Thing
Description
Specification.
The following fields MUST be contained in an action element of an Core Profile compliant TD:
| keyword | type | constraints |
|---|---|---|
| title | string | unique name among all actions |
| input | array of DataSchema | all elements of the subclasses objectSchema and dataSchema MUST only contain simple types. |
| output | array of DataSchema | all elements of the subclasses objectSchema and dataSchema MUST only contain simple types. |
The
elements
of
the
DataSchema
subclasses
ArraySchema
and
ObjectSchema
for
the
fields
input
and
output
are
restricted
to
simple
types
in
a
Thing
Description
conforming
to
the
Core
Data
Model
.
Without
this
limitation
a
higher
implementation
burden
would
be
put
on
resource
constrained
devices
(arbitrary
cascaded
arrays
and
multi-level
objects)
which
cannot
be
satisfied
by
all
consuming
devices.
The following additional constraints MUST be applied to the Interaction Affordances of a Thing Description conforming to the Core Data Model :
| keyword | type | constraint |
|---|---|---|
| forms | array of Forms |
The
Array
of
Form
of
each
action
MUST
contain
only
a
single
endpoint.
|
| format | string |
If
the
field
format
is
used,
only
formats
defined
in
section
7.3.1-7.3.6
of
[
JSON-SCHEMA
]
MAY
be
used.
|
| oneOf | string |
The
DataSchema
field
oneOf
does
not
make
sense
for
properties
and
MUST
NOT
be
used.
|
| uriVariables | Map of DataSchema |
uriVariables
MUST
NOT
be
used.
|
TODO:
- no optional parameters
- timeout
EventAffordance
class
of
section
5.3.1.5
of
the
WoT
Thing
Description
Specification.
A Thing may provide more than one event mechanism to enable a variety of consumers.
TODO:
The events section needs to be signifcantly extended and define addtional constraints to ensure OOTBI. LongPoll, WebSockets and WebHooks can be considered as initial candidates for supported protocols for the event mechanism to identify appropriate data model constraints.
The individual protocol constraints need to be defined in a respective protocol binding chapter after they have been identified/evaluated in plugfests.
The following fields MUST be present in an event element of a Core TD :
| keyword | type | constraints |
|---|---|---|
| title | string | unique name among all events |
| description | string | human readable description |
| data | set of DataSchema instances in a JSON object | only the DataSchema subclasses booleanSchema, IntegerSchema, NumberSchema, StringSchema are permitted |
The following additional constraints MUST be applied to the Event Affordances of a WoT Thing Description conforming to the profile:
| keyword | type | constraint |
|---|---|---|
| forms | array of Forms |
The
Array
of
Form
of
each
event
MUST
contain
only
a
single
endpoint.
|
| uriVariables | Map of DataSchema |
uriVariables
MUST
NOT
be
used.
|
A Thing may provide more than one event mechanism to enable a variety of consumers.
The following fields MUST be present in a form element of a Core TD :
| keyword | type | constraints |
|---|---|---|
| title | string | unique name among all events |
| description | string | human readable description |
| data | set of DataSchema instances in a JSON object | only the DataSchema subclasses booleanSchema, IntegerSchema, NumberSchema, StringSchema are permitted |
The following additional constraints MUST be applied to the Form elements of a WoT Thing Description conforming to the Core profile :
| keyword | type | constraint |
|---|---|---|
| security | string or Array of string |
security
at
form
level
MUST
NOT
be
used.
|
| scopes | string or Array of string |
scopes
MUST
NOT
be
used.
|
The "type" relationship as defined in chapter 6 of [ RFC6903 ] is reserved for indicating an instance relationship between a thing and a thing template. The Core Data Model does not put additional constraints or requirements on links. The interpretation of a link is out of scope.
The Core Data Model defines a subset of the security schemes that MAY be implemented on resource constrained devices. A security scheme MUST be defined at the thing level. The security scheme is applied to the thing as a whole, a thing may adopt multiple security schemes.
The set of security schemes supported in the Core Data Model is based on the PlugFest results. To ensure interoperability, a TD consumer, which compliant with the Core Data Model MUST support all of the following security schemes:
When using the "no security" or "Basic Auth" security schemes it is strongly recommended to use transport layer encryption.
This section defines a protocol binding which describes how a Consumer communicates with a Web Thing [ wot-architecture ] using JSON [ JSON ] payloads over the HTTP [ HTTP11 ] protocol.
A Consumer or Web Thing conforming to the WoT Core Profile MUST implement this protocol binding.
The examples provided throughout the Core Profile Protocol Binding section describe how a Consumer would communicate with a Web Thing which produces the following Thing Description:
{ "@context": "https://www.w3.org/2019/wot/td/v1", "id": "https://mywebthingserver.com/things/lamp", "profile": "https://www.w3.org/2021/wot/profile/core", "base": "https://mywebthingserver.com/things/lamp/", "title": "My Lamp", "description": "A web connected lamp", "securityDefinitions": { "oauth2": { "scheme": "oauth2", "flow": "code", "authorization": "https://mywebthingserver.com/oauth/authorize", "token": "https://mywebthingserver.com/oauth/token",
}
},
"security": "oauth2", "properties": { "on": { "type": "boolean", "title": "On/Off", "description": "Whether the lamp is turned on", "forms": [{"href": "./properties/on"}]
},
"level" : { "type": "integer", "title": "Brightness", "description": "The level of light from 0-100", "minimum" : 0, "maximum" : 100, "forms": [{"href": "./properties/brightness"}]
}
},
"actions": { "fade": { "title": "Fade", "description": "Fade the lamp to a given level", "input": { "type": "object", "properties": { "level": { "type": "integer", "minimum": 0, "maximum": 100
},
"duration": { "type": "integer", "minimum": 0, "unit": "milliseconds"
}
}
},
"forms": [{"href": "./actions/fade"}]
}
},
"events": { "overheated": { "title": "Overheated", "data": { "type": "number", "unit": "degree celsius"
},
"description": "The lamp has exceeded its safe operating temperature", "forms": [{"href": "./events/overheated"}]
}
},
"forms": [
{
"op": "readallproperties", "href": "./properties"
},
{
"op": "subscribeallevents", "href": "./events"
}
],
"links": [
{
"rel": "alternate", "type": "text/html", "href": "."
}
]
}
The informative example Canonical Thing Description provided below illustrates how a Consumer conforming to the Core Profile would interpret the above Thing Description once all of the defaults and protocol definitions from the Core Profile Protocol Binding have been applied.
readproperty
The
URL
of
a
Property
resource
to
be
used
when
reading
the
value
of
a
property
MUST
be
obtained
from
a
Canonical
TD
by
locating
a
Form
inside
the
corresponding
PropertyAffordance
for
which
the
value
of
its
op
member
is
readproperty
and
the
URI
scheme
[
RFC3986
]
of
the
value
of
its
href
member
is
http
or
https
.
In order to read the value of a property, a Consumer MUST send an HTTP request to a Web Thing with:
GET
Property
resource
Accept
header
set
to
application/json
GET /things/lamp/properties/on HTTP/1.1
Host: mythingserver.com
Accept
:
application/json
If a Web Thing receives an HTTP request following the format above and the Consumer has permission to read the corresponding property, then upon successfully reading the value of the property it MUST send an HTTP response with:
200
Content-Type
header
set
to
application/json
HTTP/1.1 200 OK
Content-Type: application/json
false
writeproperty
The
URL
of
a
Property
resource
to
be
used
when
writing
the
value
of
a
property
MUST
be
obtained
from
a
Canonical
TD
by
locating
a
Form
inside
the
corresponding
PropertyAffordance
for
which
the
value
of
its
op
member
is
writeproperty
and
the
URI
scheme
[
RFC3986
]
of
the
value
of
its
href
member
is
http
or
https
.
In order to write the value of a property, a Consumer MUST send an HTTP request to a Web Thing with:
PUT
Property
resource
Accept
header
set
to
application/json
Content-Type
header
set
to
application/json
PUT /things/lamp/properties/on HTTP/1.1
Host: mythingserver.com
Content-Type: application/json
Accept: application/json
true
If a Web Thing receives an HTTP request following the format above and the Consumer has permission to write the corresponding property, then upon successfully writing the value of the property it MUST send an HTTP response with:
204
HTTP/1.1
204
No
Content
readallproperties
The
URL
of
a
Properties
resource
to
be
used
when
reading
the
value
of
all
properties
at
once
MUST
be
obtained
from
a
Canonical
TD
by
locating
a
Form
inside
the
top
level
forms
member
for
which
the
value
of
its
op
member
is
readallproperties
and
the
URI
scheme
[
RFC3986
]
of
the
value
of
its
href
member
is
http
or
https
.
In order to read the value of all properties, a Consumer MUST send an HTTP request to a Web Thing with:
GET
Properties
resource
Accept
header
set
to
application/json
GET /things/lamp/properties HTTP/1.1
Host: mythingserver.com
Accept
:
application/json
If a Web Thing receives an HTTP request following the format above, then upon successfully reading the values of all the readable properties to which the Consumer has permission to access, it MUST send an HTTP response with:
200
Content-Type
header
set
to
application/json
HTTP/1.1 200 OK
Content-Type: application/json
{
"on": false,
"level": 100
}
writemultipleproperties
The
URL
of
a
Properties
resource
to
be
used
when
writing
the
value
of
multiple
properties
at
once
MUST
be
obtained
from
a
Canonical
TD
by
locating
a
Form
inside
the
top
level
forms
member
for
which
the
value
of
its
op
member
is
writemultipleproperties
and
the
URI
scheme
[
RFC3986
]
of
the
value
of
its
href
member
is
http
or
https
.
In order to write the value of multiple properties at once, a Consumer MUST send an HTTP request to a Web Thing with:
PUT
Properties
resource
Content-Type
header
set
to
application/json
Accept
header
set
to
application/json
PUT /things/lamp/properties HTTP/1.1
Host: mythingserver.com
Content-Type: application/json
Accept: application/json
{
"on": true,
"level": 50
}
If a Web Thing receives an HTTP request following the format above, then upon successfully writing the values of the requested writable properties it MUST send an HTTP response with:
204
HTTP/1.1
204
No
Content
Other
operations
under
consideration
include
observeproperty
,
unobserveproperty
,
observeallproperties
and
unobserveallproperties
.
These operations would require consesus on a default observe mechanism for HTTP (e.g. Server Sent Events or WebSockets).
readmultipleproperties
is
currently
excluded
due
to
the
complexities
of
the
request
payload
format
and
because
it
doesn't
add
much
functionality
over
readproperty
and
readallproperties
.
writeallproperties
is
currently
excluded
because
it
is
just
a
special
case
of
writemultipleproperties
.
invokeaction
The
URL
of
an
Action
resource
to
be
used
when
invoking
an
action
MUST
be
obtained
from
a
Canonical
TD
by
locating
a
Form
inside
the
corresponding
ActionAffordance
for
which
the
value
of
its
op
member
is
invokeaction
and
the
URI
scheme
[
RFC3986
]
of
the
value
of
its
href
member
is
http
or
https
.
In order to invoke an action on a Web Thing, a Consumer MUST send an HTTP request to the Web Thing with:
POST
Action
resource
Accept
header
set
to
application/json
Content-Type
header
set
to
application/json
POST /things/lamp/actions/fade HTTP/1.1
Host: mythingserver.com
Content-Type: application/json
Accept: application/json
{
"level": 100,
"duration": 5
}
If a Web Thing receives an HTTP request following the format above and the Consumer has permission to invoke the corresponding action, then upon successfully invoking the action it MUST send an HTTP response with:
The response to invoking an action needs to be defined. Given not all actions can be completed within the timeout period of an HTTP response, this may need to include a reference to an action request resource in an action queue (see #302 ).
queryaction
,
updateaction
and
cancelaction
.
These
operations
do
not
yet
exist
in
the
WoT
Thing
Description
specification
(see
#302
).
Other
operations
under
consideration
include
subscribeevent
,
unsubscribeevent
,
subscribeallevents
,
unsubscribeallevents
,
readpastevents
and
readallpastevents
.
subscribeevent
,
unsubscribeevent
,
subscribeallevents
and
unsubscribeallevents
would
require
consensus
on
a
default
event
subscription
mechanism
for
HTTP
(e.g.
Server
Sent
Events
or
WebSockets).
subscribeallevents
and
unsubscribeallevents
do
not
yet
exist
in
the
WoT
Thing
Description
specification
(see
#1082
).
readpastevents
and
readallpastevents
do
not
yet
exist
in
the
WoT
Thing
Description
specification
(see
#892
).
If any of the operations defined above are unsuccessful then the Web Thing MUST send an HTTP response with an HTTP error code which describes the reason for the failure. It is RECOMMENDED that error responses use one of the following HTTP error codes:
400
Bad
Request
401
Unauthorized
403
Forbidden
404
Not
Found
500
Internal
Server
Error
Web
Things
MAY
respond
with
other
valid
HTTP
error
codes
(e.g.
418
I'm
a
teapot
),
but
Consumers
MAY
interpret
those
error
codes
as
a
generic
4xx
or
5xx
error
with
no
special
defined
behaviour.
If we define the finite set of error responses as above then we should also define what a Consumer should do if it receives a 3xx redirect type response.
If an HTTP error response contains a body, the content of that body MUST conform with with the Problem Details format [ RFC7807 ].
The following informative Canonical Thing Description illustrates how a Consumer conforming to the Core Profile would interpret the example Thing Description in EXAMPLE 3 , once all of the defaults and protocol definitions from the Core Profile Protocol Binding have been applied. Whitespace and newlines have been inserted to make the example more readable.
{ "@context": "https://www.w3.org/2019/wot/td/v1", "id": "https://mywebthingserver.com/things/lamp", "profile": "https://www.w3.org/2021/wot/profile/core", "base": "https://mywebthingserver.com/things/lamp/", "title": "My Lamp", "description": "A web connected lamp", "securityDefinitions": { "oauth2": { "scheme": "oauth2", "flow": "code", "authorization": "https://mywebthingserver.com/oauth/authorize", "token": "https://mywebthingserver.com/oauth/token",
}
},
"security": "oauth2", "properties": { "on": { "type": "boolean", "title": "On/Off", "description": "Whether the lamp is turned on", "observable": false, "readOnly": false, "writeOnly": false "forms": [
{
"href": "./properties/on", "contentType": "application/json", "htv:methodName": "GET", "op": "readproperty", "security": "oauth2"
},
{
"href": "./properties/on", "contentType": "application/json", "htv:methodName": "PUT", "op": "writeproperty", "security": "oauth2"
}
]
},
"level" : { "type": "integer", "title": "Brightness", "description": "The level of light from 0-100", "minimum" : 0, "maximum" : 100, "forms": [{"href": "./properties/brightness"}]
}
},
...
}
The default representation is JSON. Semantic annotations based on JSON-LD MAY be present but are not required to perform all interactions with the thing instance.
A canonical representation serves multiple purposes. It is simplifying the parsing process, enables to identify equivalent TDs by simple string comparisons. Furthermore it allows the use of a simple signing mechanism, such as Linked Data Proofs or JSON Web Signatures [ RFC7515 ] and enables identity checks on encrypted TDs.
The canonical JSON representation format of a TD adopts the JSON Canonicalization Scheme (JCS) defined by 6292 .
A Thing Description can be syntactically validated with the JSON Schema [ JSON-SCHEMA ] for compliance with the core profile.
Todo: Define a JSON-SCHEMA.
Referenced in:
Referenced in:
Referenced in:
Referenced in: