The Vehicle Information Service Specification (VISS) is a service for accessing vehicle information, signals from sensors on control units within a vehicle's network. It exposes this information using a hierarchical tree like taxonomy defined in GENIVI Vehicle Signal Specification (VSS). The service provides this information in JSON format. The service may reside in the vehicle for applications needing to analyse a high volume of realtime data or on servers in the internet with information already brought off the vehicle.

This specification describes a second version of VISS which has been implemented and deployed on production vehicles. It adds major new capabilities and improvements to the earlier version. The first version of VISS only supported WebSocket as a transport protocol, the second version is generalized to work across different protocols as some are better suited for different use cases. HTTP is now supported with additional protocols used within the automotive industry being evaluated for inclusion. Subscription capabilities have been improved and access control has been added.

There are two parts to this specification, Core and Transport. This document, the VISS version 2 TRANSPORT specification, describes the VISSv2 transport protocols, and the mapping of the message layer on these transports. The companion specification VISSv2 CORE describes the messaging layer.

Introduction

This document describes the transport bindings of the Vehicle Information Service Specification, version 2. The split between transport bindings and messaging layer specifications improves readability and simplifies extending the specification to further transports in the future. This specification supports multiple transport bindings, namely HTTPS, secure WebSockets, and MQTT.

Terminology

The acronym 'VISSv2' is used to refer to this document, the VISS version 2 specification. The acronym 'VSS' is used to refer to the 'Vehicle Signal Specification' which is defined by the GENIVI Alliance. The term 'WebSocket' when used in this document, is as defined in the W3C WebSocket API and the WebSocket Protocol.

Transport Common Definitions

This chapter defines features that SHALL be common for all transport protocols.

Status Codes

The server implementation SHALL support the error numbers listed in the table below, with the associated reason and message fields, for all supported transport protocols.

The client SHOULD support any status code defined in [[RFC2616]].

Error Number (Code) Error Reason Error Message
304 (Not Modified) not_modified No changes have been made by the server.
400 (Bad Request) bad_request The server is unable to fulfil the client request because the request is malformed.
400 (Bad Request) filter_invalid Filter requested on non-primitive type.
401 (Unauthorized) token_expired Access token has expired.
401 (Unauthorized) token_invalid Access token is invalid.
401 (Unauthorized) token_missing Access token is missing.
401 (Unauthorized) too_many_attempts The client has failed to authenticate too many times.
401 (Unauthorized) read_only The desired signal cannot be set since it is a read only signal.
403 (Forbidden) user_forbidden The user is not permitted to access the requested resource. Retrying does not help.
403 (Forbidden) user_unknown The user is unknown. Retrying does not help.
403 (Forbidden) device_forbidden The device is not permitted to access the requested resource. Retrying does not help.
403 (Forbidden) device_unknown The device is unknown. Retrying does not help.
404 (Not Found) invalid_path The specified data path does not exist.
404 (Not Found) private_path The specified data path is private and the request is not authorized to access signals on this path.
404 (Not Found) invalid_subscriptionId The specified subscription was not found.
406 (Not Acceptable) insufficient_priviledges The priviledges represented by the access token are not sufficient.
406 (Not Acceptable) not_acceptable The server is unable to generate content that is acceptable to the client
429 (Too Many Requests) too_many_requests The client has sent the server too many requests in a given amount of time.
502 (Bad Gateway) bad_gateway The server was acting as a gateway or proxy and received an invalid response from an upstream server.
503 (Service Unavailable) service_unavailable The server is currently unable to handle the request due to a temporary overload or scheduled maintenance (which may be alleviated after some delay).
504 (Gateway Timeout) gateway_timeout The server did not receive a timely response from an upstream server it needed to access in order to complete the request.

Transport Payload

The payload SHALL have JSON format. See for the payload format of the messages for the different transport protocols.

Authorization

Clients must provide a token to the server in order to verify that it is correctly authorized for the service it requests (see CORE document).Tokens are integrated in HTTP requests in the Authorization header. For WebSockets requests an optional authorization property in the payload can be used.

Transport Protocols

The transport protocols supported are the secure versions of the HTTP and WebSockets protocols. Further transport protocols may be supported in future versions of this specification.

HTTPS

The message data components described in the CORE document are in the first hand mapped to required HTTP parameters, and only when there is no appropriate mapping it is mapped to the payload. The subscribe/unsubscribe messages are not supported by this transport protocol.

Session Life Time Management

Initialization

N/A?

Closure

N/A?

Transport Messages

Read

The client MAY send a HTTPS GET request message to the server to get one or more value(s) of one or more vehicle signal(s). If the server is able to satisfy the request it SHALL return a response containing the requested value(s). If the server is unable to fulfil the request, e.g. because the client is not authorized to retrieve one or more of the signals, then the server response SHALL have the status code set to indicate error.

Example: Request: 


              GET /Vehicle/Cabin/SeatPosCount   HTTP/1.1
              Host: 127.0.0.1:1337
              Accept: application/json
	      ...
Successful response: 

              HTTP/1.1 200 OK
              Content-Type: application/json; charset=utf-8
	      ...
              {
                “data”:{“path”:”Vehicle.Cabin.SeatPosCount”, 
                        “dp”:{“value”:[”2”, "3", "2"], “ts”:”2020-04-15T13:37:00Z”}
                       }
              }
Error response: 

              HTTP/1.1 404 Not Found
              Content-Type: application/json; charset=utf-8
	      ...
              {
                "error": {"number": 404, "reason": "invalid_path", "message": "The specified data path does not exist."}
              }

Authorized Read

JWT tokens will be sent in the Authorization header, following with term Bearer and a space character.

The following example assumes eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiSm9obiBEb2UifQ.xuEv8qrfXu424LZk8bVgr9MQJUIrp1rHcPyZw_KSsds is the actual token. A token header can be combined with all types of read requests.
Example: Request: 


            GET /Vehicle/Drivetrain/InternalCombustionEngine/RPM   HTTP/1.1
            Host:127.0.0.1:1337
            Authorization:Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiSm9obiBEb2UifQ.xuEv8qrfXu424LZk8bVgr9MQJUIrp1rHcPyZw_KSsds
Successful response: 

            HTTP/1.1 200 OK
            Content-Type: application/json; charset=utf-8
	    ...
            {
              “data”:{“path”:”Vehicle/Drivetrain/InternalCombustionEngine/RPM”, 
                      “dp”:{“value”:”2372”, “ts”:”2020-04-15T13:37:00Z”}
                     }
            }
Error response: 

            HTTP/1.1 401 Unauthorized
            WWW-Authenticate: Bearer realm="127.0.0.1:1337",
                                     error="invalid_token",
                                     error_description="The access token is invalid or expired"	    
            Content-Type: application/json; charset=utf-8
	    ...
            {
              "error": {"number": 401, "reason": "token_invalid", "message": "Access token is invalid."}
            }

Search Read

The search read request uses the query pattern described in the CORE document to provide one or more path expressions, relative to the path in the GET URL.
Example: Request: 


              GET /Vehicle/Cabin/Door?filter={"type":"paths", "value":"*/*/IsOpen"}   HTTP/1.1
              Host: 127.0.0.1:1337
              Accept: application/json
	      ...
Response: 

              HTTP/1.1 200 OK
              Content-Type: application/json; charset=utf-8
	      ...
              {
                “data”:[{“path”:”Vehicle/Cabin/Door/Row1/Left/IsOpen”, “dp”:{“value”:”false”, “ts”:”2020-04-15T13:37:00Z”}}, 
                        {...},… 
                        {“path”:”Vehicle/Cabin/Door/Row4/Right/IsOpen”, “dp”:{“value”:”true”, “ts”:”2020-04-15T13:37:00Z”}}
                       ]
              }
Error response: 

              HTTP/1.1 404 Not Found
              Content-Type: application/json; charset=utf-8
	      ...
              {
                "error": {"number": 404, "reason": "invalid_path", "message": "The specified data path does not exist."}
              }

History Read

The history read request uses the query pattern described in the CORE document to read recorded values for a given period backwards in time.
Example: Request: 


              GET /Vehicle.Acceleration.Longitudinal?filter={"type":"history", "value":"P2DT12H"}   HTTP/1.1
              Host: 127.0.0.1:1337
              Accept: application/json
	      ...
Response: 

              HTTP/1.1 200 OK
              Content-Type: application/json; charset=utf-8
	      ...
              {
                “data”:{“path”:”Vehicle.Acceleration.Longitudinal”, “dp”:[{“value”:”0.123”, “ts”:”2020-04-15T13:00:00Z”}, ..., {“value”:”0.125”, “ts”:”2020-04-15T13:37:00Z”}]}
              }

Service Discovery Read

The service discovery request uses the URL fragment pattern as described in the CORE document to retrieve the static metadata, i. e. the metadata defined in the VSS tree. The dynamic metadata, i. e. any other metadata kept by the vehicle system, is retrieved by the setting the "type" to "dynamic-metadata".
Example: Request: 


              GET /Vehicle/Drivetrain/FuelSystem?filter={"type":"static-metadata", "value":""}   HTTP/1.1
              Host: 127.0.0.1:1337
              Accept: application/json
	      ...
Response: 

              HTTP/1.1 200 OK
              Content-Type: application/json; charset=utf-8
	      ...
              {
                "metadata": {"FuelSystem":{"type":"branch","description":"Fuel system data.","children":{"HybridType, ... }}}
                "ts": "2020-04-15T13:37:00Z"
              }

Update

The client may request that the server sets the value of one or more signals e.g. to lock one or more doors or open a window by sending an HTTPS POST request to the server. In the case of several signals being set, they MUST all be of the same data type, and be set to the same value. If the server is able to satisfy the request its response SHALL have a 200 OK status code set. If an error occurs e.g. because the client is not authorized to set the requested value, or the value is read-only, the server response SHALL have the status code set to indicate error.

Example: 


              POST /Vehicle/Drivetrain/Transmission/PerformanceMode   HTTP/1.1
              Host: 127.0.0.1:1337
              Accept: application/json
	      ...
              {
                "value": "sport"
              }
Successful response: 

              HTTP/1.1 200 OK
              Content-Type: application/json; charset=utf-8
	      ...
              {
                "ts": "2020-04-15T13:37:00Z"
              }
Error response: 

              HTTP/1.1 404 Not Found
              Content-Type: application/json; charset=utf-8
	      ...
              {
                "error": {"number": 404, "reason": "invalid_path", "message": "The specified data path does not exist."}
              }

Authorized Update

JWT tokens will be sent in the Authorization header, following with term Bearer and a space character.

The following example assumes eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiSm9obiBEb2UifQ.xuEv8qrfXu424LZk8bVgr9MQJUIrp1rHcPyZw_KSsds is the actual token. A token header can be combined with all types of update requests. 


            POST /Vehicle/Drivetrain/Transmission/PerformanceMode   HTTP/1.1
            Host:127.0.0.1:1337
            Authorization:Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoiSm9obiBEb2UifQ.xuEv8qrfXu424LZk8bVgr9MQJUIrp1rHcPyZw_KSsds
            {
              "value": "sport"
            }

Secure WebSockets

As the WebSocket protocol does not implicitly provide a logical association between the request and response messages described here a key-value pair with the keyname "requestId" is added to the data components described in the CORE document. As the WebSockets protocol neither specifies a set of explicit methods, another key-value pair with the keyname "action" is also added. See for the declaration of these new key-value pairs. All data components are mapped to the payload.

Session Life Time Management

Initialization

If the client application is an HTML Application running in a web runtime or is a web page running in a browser, the WebSocket instance may either be instantiated natively or be created using a 'standards compliant' WebSocket JavaScript library.

A WebSocket can also be initiated from a native (e.g. C++) Application or from an Application written using a 'Managed Runtime' language like Java or C#. It is assumed that native and managed clients use a suitable standards compliant WebSocket library to request that a WebSocket connection is opened on the server.

Implementations that support additional devices or multiple VISSv2 services should provide discovery. Alternatively, the location of a particular VISSv2 Server instance on the local vehicle network may be handled by configuration, either as part of a package manifest or by consulting a registry on application install. The 'wwwVISSv2' hostname in this specification is used an example.

A client running on the vehicle is able to connect to the VISSv2 Server instance using the hostname e.g. 'wwwVISSv2' and uses the default port 443. The hostname 'wwwVISSv2' may locally be mapped to the localhost IP address 127.0.0.1 e.g. by adding an entry to the /etc/hosts file.

The sub-protocol name SHALL be 'VISSv2' with the digit 2 being the version number. The sub-protocol version will be associated with exactly one VISS Server Specification version so that the client and server can correctly validate and parse request and response message packets.


	var vehicle  = new WebSocket("wss://wwwVISSv2:443", "VISSv2");

The client SHALL connect to the server over HTTPS and request that the server opens a WebSocket. All WebSocket communications between the client and server MUST be over ‘wss’. Non encrypted communication is not supported, hence the server MUST refuse ‘ws’ connection requests.

This specification assumes that a single WebSocket is used to enable communication between a client application and the server. The client MAY open more than one websocket. However, the server MAY refuse to open a subsequent WebSocket connection and the client is responsible for handling this gracefully.

If more than one WebSocket connection is established between a client application and the server then each connection MUST be managed independently. For example, subscriptions created using a particular WebSocket connection shall only trigger notifications via that connection and the client MUST use that WebSocket connection to unsubscribe.

If more than one WebSocket connection has been established between one or more clients and a particular server instance, there is a risk that race conditions and concurrency issues could occur. An example of this would be where two or more WebSocket connections are used to update a particular setting at the same time.

Unless explicitly stated otherwise, the client MAY only assume that the server implements a simple concurrency model where lost updates and dirty reads could potentially occur if the server has more than one WebSocket connection open.

Closure

The WebSocket may be closed by either the client or the server by invoking the ‘close()’ method on the WebSocket instance.

The following example shows the lifetime of a WebSocket on the client:


	// Open the WebSocket
	var vehicle  = new WebSocket("wss://wwwVISSv2:443", "VISSv2");
	…
	// Close the WebSocket
	vehicle.close();

The VISSv2 Server may terminate the WebSocket connection if it has not received a request for a period determined by the server. It is the client’s responsibility to handle this gracefully and to recover and request new subscriptions, where required.

Transport Messages

Read

The client MAY send a getRequest message to the server to get the value of one or more vehicle signals. If the server is able to satisfy the request it SHALL return a getSuccessResponse message. If the server is unable to fulfil the request, e.g. because the client is not authorized to retrieve one or more of the signals, then the server SHALL return a getErrorResponse message. The structure of these message objects is defined below.


Object NameAttributeTypeRequired
getRequest
actionActionYes
pathstringYes
filterstringOptional
authorizationstringOptional
requestIdstringYes

Object NameAttributeTypeRequired
getSuccessResponse
actionActionYes
requestIdstringYes
dataobject/arrayYes

In the table above the "data" attribute is either an object containing "value" and "ts" name/value pairs, or an array of such objects.

Object NameAttributeTypeRequired
getErrorResponse
actionActionYes
requestIdstringYes
errorErrorYes
tsstringYes

Example:
Request: 


              {
                "action": "get",
                "path": "Vehicle/Drivetrain/InternalCombustionEngine/RPM",
                "requestId": "8756"
              }
Successful response: 

              {
                "action": "get",
                "requestId": "8756",
                “data”:{“path”:”Vehicle/Drivetrain/InternalCombustionEngine/RPM”, 
                        “dp”:{“value”:”2372”, “ts”:”2020-04-15T13:37:00Z”}
                       }
              }
Error response: 

              {
                "action": "get",
                "requestId": "8756",
                "error": {"number": 404, "reason": "invalid_path", "message": "The specified data path does not exist."},
                "ts": "2020-04-15T13:37:00Z"
              }

Authorized Read

If the operation on the VSS node that is addressed requires authorization, then the request must contain the field "authorization" with its value being a JWT token. The token validation must be successful for a getSuccessResponse to be returned, else a getErrorResponse is returned. A token can be combined with all types of read requests.

Example:
Request: 


              {
                "action": "get",
                "path": "Vehicle/Drivetrain/InternalCombustionEngine/RPM",
                "authorization": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1...Zw_KSsds"
                "requestId": "8657"
              }
Response: 

              {
                "action": "get",
                "requestId": "8657",
                “data”:{“path”:”Vehicle/Drivetrain/InternalCombustionEngine/RPM”, 
                        “dp”:{“value”:”2372”, “ts”:”2020-04-15T13:37:00Z”}
                       }
              }

Search Read

A client may issue a search read request to access multiple values in one request message. This is realized by adding a "filter" object following the pattern described in the CORE spec, "Filtering" chapter.

Example:
Request: 


              {
                "action": "get",
                "path": "Vehicle/Cabin",
                "filter": {"type":"paths", "value":["Door/*/*/IsOpen", "DriverPosition"]}
                "requestId": "5688"
              }
Response: 

              {
                "action": "get",
                “data”:[{“path”:”Vehicle/Cabin/Door/Row1/Left/IsOpen”, “dp”:{“value”:”false”, “ts”:”2020-04-15T13:37:00Z”}}, 
                        {...},… 
                        {“path”:”Vehicle/Cabin/Door/Row4/Right/IsOpen”, “dp”:{“value”:”true”, “ts”:”2020-04-15T13:37:00Z”}},
                        {“path”:”Vehicle/Cabin/DriverPosition”, “dp”:{“value”:”1”, “ts”:”2020-04-15T07:00:00Z”}}
                       ]
                "requestId": "5688",
              }

History Read

A client may issue a history read request to access recorded data points. This is realized by adding a "filter" object following the pattern described in the CORE spec, "Filtering" chapter.

Example:
Request: 


              {
                "action": "get",
                "path": "Vehicle.Acceleration.Longitudinal",
                "filter": {"type":"history", "value":"P2DT12H"},
                "requestId": "5688"
              }
Response: 

              {
                "action": "get",
                “data”: {“path”: ”Vehicle.Acceleration.Longitudinal”, “dp”: [{“value”: ”0.123”, “ts”: ”2020-04-15T13:00:00Z”}, {“value”: ”0.125”, “ts”: ”2020-04-15T13:37:00Z”}]},
                "requestId": "5688"
              }

Service Discovery Read

A client may issue a service discovery read request to access dynamic metadata. A successful response will contain the requested metadata from all nodes of the subtree defined by the subtree root node that is addressed by the path. The static metadata, i. e. the metadata in the VSS tree, is retrieved by the setting the "type" to "static-metadata", and the "value" to relevant static metadata.

Example:
Request: 


              {
                "action": "get",
                "path": "Vehicle/Drivetrain/FuelSystem",
                "filter":{"type":"dynamic-metadata", "value":["availability", "validate"]}
                "requestId": "5687"
              }
Response: 

              {
                "action": "get",
                "requestId": "5687",
                "metadata": {"FuelSystem":{"availability":"available","validate":"read-write","children":{"HybridType", ... }}}
                "ts": "2020-04-15T13:37:00Z"
              }

Update

The client may request that the server sets the value of one or more signals e.g. to lock one or more doors or open a window by sending a setRequest message to the server. In the case of several signals being set, they MUST all be of the same data type, and be set to the same value. If the server is able to satisfy the request it SHALL return a setSuccessResponse message. If an error occurs e.g. because the client is not authorized to set the requested value, or the value is read-only, the server SHALL return a setErrorResponse message.

Object NameAttributeTypeRequired
setRequest
actionActionYes
pathstringYes
valuestringYes
authorizationstringOptional
requestIdstringYes

Object NameAttributeTypeRequired
setSuccessResponse
actionActionYes
requestIdstringYes
tsstringYes

Object NameAttributeTypeRequired
setErrorResponse
actionActionYes
requestIdstringYes
errorErrorYes
tsstringYes

Example:
Request: 


              {
                "action": "set",
                "path": "Vehicle/Drivetrain/Transmission/PerformanceMode",
                "value": "sport",
                "requestId": "5687"
              }
Successful response: 

              {
                "action": "set",
                "requestId": "5687",
                "ts": "2020-04-15T13:37:00Z"
              }
Error response: 

              {
                "action": "set",
                "requestId": "5687",
                "error": {"number": 404, "reason": "invalid_path", "message": "The specified data path does not exist."},
                "ts": "2020-04-15T13:37:00Z"
              }

Authorized Update

If the operation on the VSS node that is addressed requires authorization, then the request must contain the field "authorization" with its value being a JWT token. The token validation must be successful for a setSuccessResponse to be returned, else a setErrorResponse is returned. A token can be combined with all types of update requests.

Example:
Request: 


              {
                "action": "set",
                "path": "Vehicle/Drivetrain/Transmission/PerformanceMode",
                "value": "sport",
                "authorization": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1...Zw_KSsds"
                "requestId": "5687"
              }
Response: 

              {
                "action": "set",
                "requestId": "5687",
                "ts": "2020-04-15T13:37:00Z"
              }

Subscribe

The client may send a subscribeRequest message to request a subscription to one or more signals, thereby requesting the server to repeatedly return subscription notification messages, as specified by the "filter" query (see CORE, "Filtering" chapter). The server MAY reduce the number of subcriptionNotification messages sent to the client in order to reduce processing demands.
If the server is able to satisfy the request it SHALL return a subscribeSuccessResponse message. If an error occurs e.g. because the client is not authorized to set the requested value, the server SHALL return a subscribeErrorResponse message.
The subscription variants are, as described in the CORE document:

  • time-based: notifications are issued at a regular time interval,
  • change: notifications are issued when the value has changed as specified,
  • range: notifications are issued when the value is in the specified range,
  • curve-logging: notifications are issued when the buffer is full, and then processed according to the curve logging algorithm.

Object NameAttributeTypeRequired
subscribeRequest
actionActionYes
pathstringYes
filterstringOptional
authorizationstringOptional
requestIdstringYes

Object NameAttributeTypeRequired
subscribeSuccessResponse
actionActionYes
requestIdstringYes
subscriptionIdstringYes
tsstringYes

Object NameAttributeTypeRequired
subscribeErrorResponse
actionActionYes
requestIdstringYes
errorErrorYes
tsstringYes

Object NameAttributeTypeRequired
subscriptionNotification
actionActionYes
subscriptionIdstringYes
dataobject/arrayYes

Object NameAttributeTypeRequired
subscriptionErrorNotification
actionActionYes
subscriptionIdstringYes
errorErrorYes
tsstringYes

Example:
Request: 


              {
                "action": "subscribe",
                "path": "Vehicle/Drivetrain/FuelSystem/Level",
                "filter": {"type":"timebased", "value":{"period":"3"}}
                "requestId": "6578"
              }
Successful response: 

              {
                "action": "subscribe",
                "subscriptionId": "12345",
                "requestId": "6578",
                "ts": "2020-04-15T13:37:00Z"
              }
Error response: 

              {
                "action": "subscribe",
                "requestId": "6578",
                "error": {"number": 404, "reason": "invalid_path", "message": "The specified data path does not exist."},
                "ts": "2020-04-15T13:37:00Z"
              }
Notification: 

              {
                "action": "subscription",
                "subscriptionId": "12345",
                “data”: {“path”: ”Vehicle/Drivetrain/FuelSystem/Level”, 
                        “dp”: {“value”: ”50”, “ts”: ”2020-04-15T13:37:00Z”}
                },
                "ts": "2020-04-15T13:37:00Z"
              }
Error notification: 

              {
                "action": "subscription",
                "subscriptionId": "12345",
                "error": {"number": 401, "reason": "token_expired", "message": "Access token has expired."},
                "ts": "2020-04-15T13:37:00Z"
              }

Authorized Subscribe

If the operation on the VSS node that is addressed requires authorization, then the request must contain the field "authorization" with its value being a JWT token. The token validation must be successful for a subscribeSuccessResponse to be returned, else a subscribeErrorResponse is returned. An "authorization" key-value pair can be combined with all types of subscription requests.

Example:
Request: 


              {
                "action": "subscribe",
                "path": "Vehicle/Drivetrain/FuelSystem/Level",
                "filter": {"type":"range", "value":[{"logic-op":"gt", "boundary":"49"}, {"logic-op":"lt", "boundary":"51"}]},
                "authorization": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1...Zw_KSsds",
                "requestId": "6578"
              }
Successful response: 

              {
                "action": "subscribe",
                "subscriptionId": "12345",
                "requestId": "6578",
                "ts": "2020-04-15T13:37:00Z"
              }
Notification: 

              {
                "action": "subscription",
                "subscriptionId": "12345",
                “data”: {“path”: ”Vehicle/Drivetrain/FuelSystem/Level”, 
                        “dp”: {“value”: ”50”, “ts”: ”2020-04-15T13:37:00Z”}
                },
                "ts": "2020-04-15T13:37:00Z"
              }

Curve Logging Subscribe

Curve logging data compression by eliminating data points that are within a set error margin is activated via a subscription request. Notifications will be issued when the buffer becomes full, after insignificant data points have been eliminated.

Example:
Request: 


              {
                "action": "subscribe",
                "path": "Vehicle/Drivetrain/FuelSystem/Level",
                "filter": {"type":"curvelog", "value":{"maxerr":"0.5", "bufsize":"100"}},
                "requestId": "6578"
              }
Successful response: 

              {
                "action": "subscribe",
                "subscriptionId": "12345",
                "requestId": "6578",
                "ts": "2020-04-15T13:37:00Z"
              }
Notification: 

              {
                "action": "subscription",
                "subscriptionId": "12345",
                “data”:{“path”: ”Vehicle/Drivetrain/FuelSystem/Level”, 
                        “dp”:[{“value”: ”50”, “ts”: ”2020-04-15T13:00:00Z”}, ..., {“value”: ”25”, “ts”: ”2020-04-15T13:37:00Z”}]
                },
                "ts": "2020-04-15T13:37:00Z"
              }

Unsubscribe

To unsubscribe from a subscription, the client SHALL send an unsubscribeRequest message to the server. If the server is able to satisfy the request it returns an unsubscribeSuccessResponse message. If an error occurs, for example because an invalid subscriptionId is passed to the server, an unsubscribeErrorResponse message is returned.
If the client has created more than one WebSocket instance, it MUST always unsubscribe using the same WebSocket instance that was originally used to create the subscription.

Object NameAttributeTypeRequired
unsubscribeRequest
actionActionYes
subscriptionIdstringYes
requestIdstringYes

Object NameAttributeTypeRequired
unsubscribeSuccessResponse
actionActionYes
subscriptionIdstringYes
requestIdstringYes
tsstringYes

Object NameAttributeTypeRequired
unsubscribeErrorResponse
actionActionYes
subscriptionIdstringYes
requestIdstringYes
errorErrorYes
tsstringYes

Example:
Request: 


              {
                "action": "unsubscribe",
                "subscriptionId": "12345",
                "requestId": "5786"
              }
Successful response: 

              {
                "action": "unsubscribe",
                "subscriptionId": "12345",
                "requestId": "5786",
                "ts": "2020-04-15T13:37:00Z"
              }
Error response: 

              {
                "action": "unsubscribe",
                "requestId": "6578",
                "error": {"number": 404, "reason": "invalid_subscriptionId", "message": "The specified subscription was not found"},
                "ts": "2020-04-15T13:37:00Z"
              }

MQTT

Application Level Protocol

For MQTT to support the complete VISSv2 interface, as decribed in the "Interface" chapter of the CORE specification, an application level protocol that runs on top of MQTT is added. It is described in the following, please also see the sequence diagram below. To emulate the client-server pattern that is described in the CORE specification, the vehicle server, via its vehicle client, issues a subscribe request to the broker on a topic named VID/Vehicle, where VID is an identity that uniquely links to the vehicle in the access control ecosystem.
The client on the "cloud side" of the broker is expected to have access to this vehicle identity. How it obtains it is out of scope for this specification. When the cloud client wants to issue a request to the vehicle server it first generates a unique topic name, which it subscribes to at the broker. It then generates a JSON formatted payload with the general structure
{"topic":"aUniqueTopic", "request":"VISSv2Request"}
where "aUniqueTopic" is the uniques topic name it just subscribed to, and "VISSv2Request" is the request for the vehicle server. This request MUST follow the payload format that is specified in the Websocket chapter of this specification. This JSON message is then issued to the broker, associated to the topic VID/Vehicle. This message will then be forwarded by the broker to the vehicle client, which forwards the string being the value of the "request" key in the message to the vehicle server. When the vehicle client receives the response to this request, it publishes it to the broker associated with the topic name that was the string value of the "topic" key name in the message it previously received from the broker.
The broker will then forward this message to the cloud side client that earlier subscribed to this topic name, which concludes the client-server based request-response as described in the CORE specification.
In the case of subscription requests the vehicle client needs to save the subscriptionId found in the subscribe response, together with the topic name associated to the subscribe request. When the vehicle server later issues notifications, the vehicle client must parse the subscriptionId from it, and retrieve the topic name associated to it. The vehicle client shall delete the saved topic name and subscriptionId when it receives an unsubscribe request in a message from the broker.
In following requests from the cloud side client, the unique topic name may be reused from the previous request-response cycle, or a new unique topic name may be generated. If a new topic name is generated, an unsubscribe should be issued on the old topic name. The vehicle client can continue to use the topic name it subscribes to.
The payload format of the responses/notifications SHALL follow the payload format that is specified in the Websocket chapter of this specification. The access control model is applicable also over this transport alternative. The Access Token server should then implement its own version of the application level protocol described here, using the topic name "VID/ATS". The Access Grant Token server may also do the same, with the topic name "VID/AGTS", or if it is deployed in the cloud it may expose the HTTP interface that is defined in this specification. VISSv2 over MQTT.

Security Aspects

The MQTT architecture mandates a "broker" that acts as a middleman in between the client and server endpoints (the subscriber and the publisher in MQTT terminology). This broker has full access to the plaintext communication between the two endpoints as each of the endpoint's TLS channel terminates at the broker. This aspect should be considered when selecting to use the MQTT protocol.

Transport Messages

As mentioned in the "Application Level Protocol" chapter, the "request" messages issued to the broker contains two JSON formatted key-value pairs, where the value of the "request" key is a string that contains the request the vehicle server will receive. The format of this request MUST follow the payload format that is specified in the Websocket chapter of this specification.

Definitions

Term Definitions

Attribute Type Description
action Action The type of action requested by the client or delivered by the server.
path String The path to a node in the VSS tree, as defined by the Vehicle Signal Specification (VSS).
requestId String Unique id value specified by the client. Returned by the server in the response and used by the client to link the request and response messages. The value MAY be an integer or a Universally Unique Identifier (UUID).
subscriptionId String Value returned by the server to uniquely identify each subscription. The value MAY be an integer or a Universally Unique Identifier (UUID).
authorization string A JWT formatted security token.
data object/array Contains a path and one or more data points.
dp object/array The data point contains a value and a timestamp.
ts string The Coordinated Universal Time (UTC) time stamp that represents the capture of the value.
value string The data value associated with the path.
filter string Provides a filtering mechanism to reduce the demands of a subscription on the server. Query format, see CORE:Filtering chapter.
metadata object Metadata describing the potentially available signal (sub)tree.
error Error Returns an error code, reason and message.

JSON Schema Definitions

The payload that is sent over the supported transport protocols SHALL use the JSON definitions in this appendix, unless otherwise specified in the VISSv2 TRANSPORT specification.
The definitions within this section describe the datatypes referenced within the JSON Schema for the VISSv2 WebSocket interfaces, and for the VISSv2 HTTP payloads. 


{
    "definitions": {
        "action": {
            "enum": [ "get", "set", "subscribe", "subscription", "unsubscribe"],
            "description": "The type of action requested by the client and/or delivered by the server",
        },
        "requestId": {
            "description": "Returned by the server in the response and used by the client to link the request and response messages.",
            "type": "string"
        },
        "path": {
            "description": "The path to the desired vehicle signal(s), as defined by the metadata schema.",
            "type": "string"
        },
        "ts": {
            "description": "The Coordinated Universal Time (UTC) time that represents the capture of the data (see chapter Timestamps in CORE).",
            "type": "string"
        },
        "filter": {
            "description": "May be specified in order to throttle the demands of subscriptions on the server. See CORE:Filtering chapter",
            "type": "string"
        },
        "subscriptionId":{
            "description": "Integer handle value which is used to uniquely identify the subscription.",
            "type": "string"
        },
        "metadata":{
            "description": "Metadata describing the potentially available signal tree.",
            "type": "object"
        },
        "data": {
            "description": "Data including path and one or more data point(s).",
            "type": "object/array",
            "properties": {
                "path": {
                    "description": "The path to the desired vehicle signal(s), as defined by the metadata schema.",
                    "type": "string"
                },
                "dp": {
                    "description": "Data point including one or more value and time samp",
                    "type": "object/array"                   
                    "properties": {
                        "value": {
                            "description": "The value related to the associated path.",
                            "type": "string"                    
                        },
                        "ts": {
                            "description": "Timestamp associated with the value capture.",
                            "type": "string"                    
                        }
                }
            }   
        },
        "error": {
            "description": "Server response for error cases",
            "type": "object",
            "properties": {
                "number": {
                    "description": "HTTP Status Code Number",
                    "type": "integer"                   
                },
                "reason": {
                    "description": "Pre-defined string value that can be used to distinguish between errors that have the same code",
                    "type": "string"                    
                },
                "message": {
                    "description": "Message text describing the cause in more detail",
                    "type": "string"                    
                }
            }   
        }
    }
}

Action Definitions

The Action enumeration is used to define the type of action requested by the client. All client messages MUST contain a JSON structure that has an action name/value pair and the value of the action property MUST be one of the values specified in the enumeration:

get
Enables the client to read one or more values.
set
Enables the client to update one value.
subscribe
Enables the client to request notifications containing a JSON data structure with values for one or more vehicle signal.
unsubscribe
Enables the client to request that it should no longer receive notifications based on that subscription.
subscription
Enables the server to send notifications to the client containing a JSON data structure with values for one or more vehicle signals.

Error Definitions

The error number SHOULD be a status code defined in [[RFC2616]], c. f. chapter "Status codes". The error reason SHOULD be the corresponding reason-phrase from [[RFC2616]]. The error message is meant to give a more precise description of the error.

Object NameAttributeTypeRequired
Error
numberintegerYes
reasonstringYes
messagestringYes