improve implementation

[RolandJentschETAS]

This pull request updates the implementation guidelines and related process documentation to clarify the expectations for detailed design, unit decomposition, and traceability, with a focus on aligning with ISO 26262 and ASPICE requirements. The changes emphasize that the source code structure and comments serve as the primary documentation and traceability mechanism, while static diagrams and separate detailed design documents are optional for most cases. The requirements for documenting design decisions and enforcing safety-related coding principles are also strengthened.

Guideline and Process Documentation Updates:

• The detailed design is now primarily captured in the source code (unit interfaces, contracts, and comments), with separate documentation being optional and only required for complex cases. Design decisions and their rationale must be documented close to the code. [1] [2]
• Traceability from components to units is achieved mainly through the directory and file structure, removing the need for explicit linking or per-unit static diagrams. Static and dynamic diagrams are now optional and only required when they help explain complex components. [1] [2]
• The basis for unit testing is clarified: unit tests verify the detailed design as specified in the code, and direct linking to component requirements is only needed in exceptional cases where a unit fully realizes a requirement. [1] [2]

Safety and Coding Standards:

• For safety-related (ASIL) units, specific ISO 26262 design and coding principles are listed and must be enforced via coding guidelines and static analysis tools. For QM units, these activities apply but the ISO-specific principles are only binding for ASIL units.

Process Requirements:

• A new process requirement mandates that the rationale for detailed design decisions (especially those affecting unit decomposition) must be documented and justified near the design, either in code or in optional detailed design documents.
• The static diagram requirement is now optional, with guidance that the file/directory structure provides the primary representation of unit decomposition.

Other Minor Updates:

• The guideline version is incremented to 3.

These changes streamline the documentation process, reduce unnecessary artifacts, and ensure compliance with safety and process standards by embedding traceability and rationale directly in the codebase.

[github-actions]

The created documentation from the pull request is available at: docu-html

[RolandJentschETAS]

@copilot resolve the merge conflicts in this pull request