> For the complete documentation index, see [llms.txt](https://www.sdv.guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.sdv.guide/sdv101/part-c-building-blocks/building-blocks-of-an-sdv/service-oriented-architecture/the-soa-framework-for-sdvs.md).

# The SOA Framework for SDVs

The SOA framework for SDVs encompasses both **on-board** and **off-board** environments, integrating **QM** (Quality Management) environments for agile application development and **ASIL** (Automotive Safety Integrity Level) environments for first-time-right safety-critical applications.

<figure><img src="/files/s3NtyDyaHM4nwJQEbyNR" alt=""><figcaption></figcaption></figure>

Here’s how the SOA Framework for SDVs is structured:

**1. Cloud Runtime**

At the heart of the off-board system, the **cloud runtime** enables scalable and agile development for microservices. It ensures seamless integration with on-board systems, allowing continuous updates, data processing, and application enhancement in a centralized environment.

**2. Vehicle-to-Cloud API**

The **vehicle-to-cloud API** acts as a bridge between on-board and off-board environments. It facilitates communication between vehicle systems and cloud platforms, ensuring that data and functionalities flow bidirectionally in a secure and efficient manner.

**3. Container Runtime**

To execute SDV functions on-board, a **container runtime** is essential. It provides the modular infrastructure needed for running microservices independently, ensuring scalability, fault tolerance, and agility. The container runtime supports parallel development and efficient deployment, allowing for quicker updates and testing.

**4. Signal-to-Service APIs**

At the core of SOA, **signal-to-service APIs** transform raw signals from sensors, actuators, and ECUs into higher-level services. This abstraction layer simplifies interaction with complex vehicle systems, enabling application developers to focus on creating functionalities without worrying about the underlying hardware complexity.

**5. Signal-Oriented Embedded Runtimes**

Embedded runtimes leverage signal-oriented designs to optimize real-time performance and ensure smooth operation of on-board systems. These runtimes interact with the signal-to-service APIs and containerized microservices, orchestrating critical processes in SDVs with minimal latency and high reliability.

## **On-Board SOA Building Blocks**

* **Endpoint ECUs**: These lower-level control units connect to sensors and actuators through local bus networks. They transmit data to zonal controllers.
* **Zonal Controllers**: Higher-end ECUs that host **signal-to-service APIs**, creating a bridge between hardware and software services.
* **Microservices**: SOA enables the development of lightweight microservices:
  * **Basic Microservices**: Simple, standalone services performing specific tasks.
  * **Composite Microservices**: Higher-order services that combine multiple basic services into more complex functionalities.

## **End-to-End Service Chains**

SOA supports the creation of **end-to-end service chains** that span on-board and off-board environments:

* In the **cloud**, microservices can access vehicle functions through vehicle-to-cloud APIs, interacting with sensors and actuators at the signal level via signal-to-service APIs.
* On-board, these APIs enable agile development for QM functionalities, with future support planned for ASIL A and B functionalities.

## **The Future of SOA**

SOA enables seamless communication across the vehicle, cloud, and external ecosystems, driving flexibility, scalability, and safety. As the architecture evolves, signal-to-service APIs will increasingly support safety-critical applications, pushing the boundaries of **software-defined vehicles**. This convergence of on-board and off-board services is central to building robust and future-proof SOA frameworks.