Technical Specification (TS) for space profile

[Sebastian Huber]

A Technical Specification (TS) is required by ​ECSS-E-ST-40C and consists of

• the Software Requirements Specification (SRS, ECSS‐E‐ST‐40C Annex D), and
• the Software Interface Control Document (ICD, ECSS‐E‐ST‐40C Annex E).

There is currently no requirements document for RTEMS. Requirements must be reverse engineered from the documentation, the source code and the tests. The TS will be created for the space profile of RTEMS SMP. It should be easy to extend the TS so that more functionality can be covered once the ground work is done.

​ECSS-E-ST-10-06C places requirements on requirements and the specification content.

We need a format for requirements. One idea is to define a custom XML data model for RTEMS requirements and use an XML document to store the requirements in the RTEMS kernel repository (requirements master document, RMD). The RMD can be used to generate human readable documents via Sphinx.

ECSS-E-ST-10-06C and ECSS-E-ST-40C mandate some of traceability information:

1. ECSS-E-ST-10-06C, 8.2.3 Configuration management and traceability: The history of requirements shall be traceable. In the XML documents the history of requirements changes, removals, additions, etc. could be stored in a special section along with additional information, e.g. reason for change, date, approval status, etc. A Git pre-commit hook could check that changes in the requirements document follow a specified procedure, e.g. one commit may change at most one requirement and there must be a corresponding revision entry for this change.

2. ECSS-E-ST-10-06C, 8.2.3 Configuration management and traceability: If a requirements is derived from other requirements, then this information must be visible (backward traceability).

3. ECSS-E-ST-40C, 5.8.3.3 Verification of the software architectural design: Each software component shall provide a link to the requirements it implements (forward traceability). Software architectural design to requirements traceability matrices shall be provided.

4. ECSS-E-ST-40C, 5.8.3.5 Verification of code: Source code shall be traceable to design and requirements. Software code traceability matrices shall be provided.

5. ECSS-E-ST-40C, 5.8.3.6 Verification of software unit testing (plan and results): Unit test shall be traceable to software requirements. Software unit tests traceability matrices shall be provided.

The presentation in a human readable form of the traceability information should be done by tools using the RMD as input and the overall source code with requirement link annotations. This requires that we have a human and machine readable requirements identifier (also ECSS-E-ST-10-06C, 8.2.6 Identifiability).