Tool Chain

A tool chain refers to a sequence of software tools used together in a development, verification, or validation process. It's a series of interconnected software applications, each performing a specific task, with the output of one tool often serving as the input for the next. This integrated set of tools supports activities throughout the safety lifecycle, from initial requirements definition and modeling through coding, testing, and deployment.

Tools used in safety-critical development can include:

• Requirements management systems

• Modeling tools

• Compilers

• Debuggers

• Static analyzers

• Testing frameworks

• Configuration management systems

The effectiveness and reliability of the entire tool chain are critical because any weakness or error introduced by a single tool can potentially compromise the safety of the final system.

Understanding the tool chain is essential, as the tools used directly impact the quality, correctness, and safety of the critical systems being developed. Functional safety standards such as ISO 26262, IEC 61508, DO-178/330 or EN 50128 require confidence that the tools used do not introduce errors or fail to detect errors that could lead to hazardous situations.

Because these tools are instrumental in creating, verifying, and validating the final product, their proper selection, integration, and qualification (if necessary) are fundamental steps in achieving functional safety compliance. ISO 26262 emphasizes the need to evaluate the confidence in the tools used in safety-related development.

ISO 26262 addresses tool chains primarily in Part 8, Clause 11, which focuses on the confidence in the use of software tools. The standard recognizes that tools are essential but also pose potential risks. It requires companies to identify the tools used in their safety lifecycle and evaluate their potential impact on achieving safety requirements.

This evaluation involves Tool Classification (determining the potential of a tool to introduce or fail to detect errors) and, based on that classification and the required Tool Confidence Level (TCL), potentially Tool Qualification. A well-defined and classified tool chain is a cornerstone of the safety case for complex automotive systems.

Yes, tool chains frequently span across different teams within an organization or even across multiple companies collaborating on a project. In the automotive industry, it's common for OEMs (Original Equipment Manufacturers) to work with Tier 1 suppliers, who in turn work with other suppliers. Each entity in this complex ecosystem may use its own set of tools, which need to interface and function together seamlessly as part of a larger, distributed tool chain.

Managing and ensuring the integrity of a distributed tool chain adds complexity. It requires clear interfaces, standardized data formats, and a shared understanding of the tool qualification requirements across all parties involved.

Establishing trust in the outputs generated by tools used by different partners is a key challenge that needs to be addressed through coordinated tool evaluation and qualification efforts as part of the overall safety management activities. This collaborative approach is essential for the successful development of safe systems in today's interconnected development environment.