The Vehicle Information Service Specification (VISS) is a service for accessing vehicle information, including signals from sensors on control units within a vehicle's network. This information is exposed through a hierarchical, tree-like taxonomy as defined in the COVESA Hierarchical Information Model (HIM), and is provided in JSON format. The VISS service may be hosted within the vehicle or on external servers, using data that has already been off-boarded.

VISS enables a broad range of use cases, including predictive maintenance, usage-based insurance, fleet management, and real-time driver assistance services. In the context of artificial intelligence, VISS serves as a critical data access layer, providing high-quality, real-time vehicle data that can be utilized by AI algorithms for tasks such as anomaly detection, driver behavior analysis, energy optimization, and contextual decision-making.

The first version of VISS, which has been implemented and deployed in production vehicles, supported only WebSocket as a transport protocol.
The second version is generalized to work across also the HTTP and MQTT transport protocols to improve the support for different use cases. It also contains improved subscription capabilities and added an access control mechanism.
The third version included the gRPC transport protocol but also simplified addition of other transport protocols by placing the normative requirement on the message payload only, and not also on what transport protocol to use. Several new features were added such as file transfer, payload encoding, and improved server capabilities representation.
The version 3.1 specification is a backwards compatible extension of the third version of VISS. Instead of referencing to the VSS rule set for how to define the content of a tree it refers to the HIM data profile rule set. This enables also other trees than the VSS tree to be used, a server may manage a set of trees, a forest, that a client can access. Other changes are minor adaptations to support the concept of having a forest of trees, such as adding support for a client to do a forest inquiry. It also includes support for the Unix domain socket transport protocol.
There are three parts to the VISS specification, [[CORE]], [[TRANSPORT]], and [[PAYLOAD_ENCODING]]. The [[CORE]] document describes the messaging layer, the [[TRANSPORT]] document describes the deviations form the CORE specification that are used by some transport protocols, and the [[PAYLOAD_ENCODING]] document describes payload encodings that are supported.

This document, the VISS Implementation Guideline version, provides recommendations on how to implement certain features to ensure implementation interoperability. The versioning of this document is decoupled from the versioning of the VISS specification. For guideline chapters that are not applicable to older versions of VISS, this shall be mentioned in the chapter.

Revision history

Introduction

This document supplements the VISS specification by providing recommendations on how to implement certain aspects of the specification. Thesa aspects are typically not explicitly exposed in the VISS interface but different implementations may lead to different behaviors leading to clients receiving different responses from different implementations. This may make interoperability more complicated to achieve, i. e. that a client shall be able to exercise the interface with any implementation of it.

Terminology

The acronym 'VISSv3.1' is used to refer to this document, the VISS version 3.1 specification. The acronym 'HIM' is used to refer to the 'Hierarchical Information Model' which is hosted by COVESA. The acronym 'VSS' is used to refer to the 'Vehicle Signal Specification' which is hosted by COVESA. The term 'WebSocket' when used in this specification, is as defined in the W3C WebSocket API and [[RFC6455]], the WebSocket Protocol.

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