RXF Cert


The RXF can be bought in a version that is certifiable. So that does not mean it is certified. It is certifiable. That means we have done all work that is done in a certification process, like writing down requirements, connecting them with model elements, creating tests, performing tests and caring about MISRA, coverage etc.

What is the RXF?

It is not an RTOS or an RTE or any other Operating System, also not a driver layer that will give you hardware control.
It is just the functionality that the UML offers that is not available in ‘C’ or ‘C++’. Much of that functionality is implemented by using an RTOS. the RXF is than a sort of Abstraction Layer that makes a unified RTOS API.

When you create an active Class in the UML you tell your audience that this class runs in its own thread. (Or Task or even process but that has some additional difficulties see this article.) This class then should have behaviour, described in either a state-machine or an activity diagram, as it is defined in the UML. There is no other “standard” mechanism, you have to build that yourself. (Remember, the UML is a language, nothing more)

When you use timers in your behaviour diagrams ( like tm(xxx) in a state-machine ) then you will have to use something that times. Either a hardware timer or if you use an RTOS you can use the tick time. But either way: there is no standard ‘C’ or ‘C++’ mechanism for that.

The RXF also takes care of sending and receiving asynchronous events that are used in state-charts.

Certified vs Certifiable

It is very difficult to certify a “half-product” like the RXF. You have to predict all possible uses and much of the functionality depends on the rest of the system. So at best it can be made certifiable. That means that all possible work for a certification is already done, many documents are already there. If you have never gone through a certification process, this is an excellent starting point. The use of modelling is more or less recommended by an increasing number of certification institutes ( They tend to be quite conservative and that is OK! ) so using Rhapsody and the RXF is a huge step forward for setting up your own process.

What is there in the RXF-Cert?

  • Bill of Material (BOM)
    Contains a directory of all documents and deliveries. With exact version numbers and MD5 hashes. Also describes the RXF-Cert system borders and its influences on software development and code generation.
  • RXF-Cert Architectural Model (RCM)
  • High Level Requirements and Specification (SPEC)
  • Requirement Traceability Table (RTT)
    Showing full coverage of requirements through system specifications down to module specifications / implementation and tests.
  • User Manual (UM)
    How to use the RXF in Rhapsody. Includes installation guide and detailed technical descriptions of the RXF-Cert.
  • Validation Plan (ValP) and Validation Report (ValR)
    Describes how we validate the RXF-Cert. Documents reviews of requirements, code and documentation. (Four-eye principle)
  • Test Documentation: Verification Plan (VerP) and Verification Report (VerR)
    • Test Concept and Test Process Description
    • Acceptance Test Specification and Results
    • System Test Specification and Results
    • Unit Test Specification and Results (Model Based using the TestConductor)
    • MISRA Conformance Report:
      how MISRA compliance is implemented and what is done to certify that violations are handled correctly
    • All Tests are part of the delivery and can be re-executed by the customer.
  • Software Safety Plan
    Describes the strategy of safe software development we have followed during development of the RXF-Cert. Explains traceability, document review guidelines and our personal competence.
  • Software Safety Manual
    How is the RXF-Cert intended to be used, what are the restrictions and safety application conditions. Also contains a description of all the functions of the RXF that can be directly called by the user.
  • Tool Manual (TM)
    Lists all tools used in RXF-Cert development including reason for usage, classification, statements for safety related usage and detailed version information.
  • Software Modification Procedure (SMP)
    How modifications and updates of the RXF-Cert are handled.
  • Final Delivery Report (FDR)
    Documents final checks that have been performed when delivering the RXF-Cert.

Vacation time

So. That is what the RXF-Cert is really doing. Literally man-years were invested in creating that. As said, it is a great start for someone who needs to certify his software, many of the pitfalls are already covered.

So. It’s August, it’s vacation time. For me, unfortunately, there is no beach or mountains,, I am moving from my old house to my new house. The latter is not finished so I have to stay in a holiday home for about 4 months. So a sort of vacation… Luckily there is internet there so I will keep writing, don’t worry!

Sunny modelling with Rhapsody and the RXF

Walter van der Heiden ( wvdheiden@willert.de )

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