QP/C  7.3.3
Real-Time Embedded Framework
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Software Requirements Specification


Purpose and Scope

This document (Unique Identifier: DOC-QP-SRS) describes the general software requirements for the QP Real-Time Embedded Framework (RTEF) as well as the most important concepts and context of use of the QP Framework. This requirements specification is designed to be most helpful to the QP Application developers, who are also the primary users of the QP Framework.

This document is part of the QP/C Certification Kit, which has been specifically designed to aid companies in safety certification of their software based on the QP/C Framework treated as commercial off-the-shelf (COTS) software.

Revision History

The revision history of the document DOC-QP-SRS is as follows:

Revision QP/C
By Description
0.0.0 7.3.0 2023-06-30 MMS Initial Release
0.0.1 7.3.2 2024-01-08 MMS Updated


About QP Framework

QP Real-Time Embedded Framework (QP Framework) is a lightweight implementation of the Active Object model of computation specifically tailored for real-time embedded (RTE) systems (such as ARM Cortex-M based MCUs). QP is both a software infrastructure for building QP Applications consisting of Active Objects (Actors) and a runtime environment for executing the Active Objects in a deterministic fashion. Additionally, QP Framework supports Hierarchical State Machines with which to specify the behavior of Active Objects [UML-2.5], [Sutter:10], [ROOM:94].

The features and requirements specified in this document can be ultimately implemented in various programming languages, so this document pertains to a whole family of QP RTEFs, currently consisting of QP/C and QP/C++ frameworks implemented in C and C++, respectively. Other possible implementations (e.g., QP/Rust) of these requirements and features might be added in the future.

QP Framework and Functional Safety

In the context of functional safety standards and certification, QP/C offers numerous advantages over the traditional "shared state concurrency" based on a "naked" Real-Time Operating System (RTOS). QP/C implements an inherently safer model of concurrency and many best practices recommended by functional safety standards (e.g., IEC 61508-7) such as:

  • Structured methods (IEC 61508-7-C.2.1)
  • Semi-formal methods, such as Hierarchical State Machines (IEC 61508-7-Table.B.7)
  • Computer-aided design tools (IEC 61508-7-B.3.5)
  • Defensive programming, including Failure Assertion Programming (IEC 61508-7-C.2.5)
  • Modular approach (IEC 61508-7-Table.B.9)
  • Design and coding standards, including safe subsets of C or C++ (IEC 61508-7-C.2.6)
  • Structured programming (IEC 61508-7-C.2.7)
  • Traceability between requirements and software design (IEC 61508-7-C2.11)


This requirements specification is primarily intended for:

  • Application Developers who develop QP Applications based on the QP Framework.

This requirements specification can also be of interest to:

  • Test Engineers,
  • Quality-Assurance Engineers,
  • Software Architects,
  • System Engineers,
  • Hardware Engineers, as well as
  • Managers who oversee the software development.

Figure SRS-01: Users and main use cases of QP Framework

Document Conventions

This requirements specification contains general requirements for the QP Framework. The separate Safety Requirement Specification [DOC-QP-SSR] contains requirements related to functional safety.

The Software Safety Requirements typically cannot be satisfied by the QP Framework alone because they capture the assumptions made in the QP Framework as to how the QP Application needs to operate. In case such safety requirements for the QP Application are not satisfied, QP Framework cannot guarantee the correct execution of the QP Application.

General Requirement UIDs

This requirements specification uses the Unique Identifiers (UIDs) with the following structure:

+++--------------- 1. work artifact class ('REQ' for Requirement)
||| ++------------ 2. Project identifier (here 'QP' for QP Framework or 'QA' for QP Application)
||| || ++-+++----- 3. work artifact ID (see note below)
||| || || ||  +--- 4. optional variant letter ('A', 'B', 'C'...)
||| || || ||  |+-- 5. optional version number (1, 2, 3...)
||| || || ||  ||

Examples: REQ-QP-01_30, REQ-QP-02_32

Use of Shall/Should/etc.

Requirement definitions use consistent terminology to indicate whether something is mandatory, desirable, or allowed.


Shall is used to denote mandatory behavior.


Should is used to denote a desirable behavior that should typically occur but might not happen all the time or might be optional in exceptional cases. The special cases are typically clarified in sub-requirements.


Mayis used to denote allowed behavior that is optional but possible.

"must not"

Must not is used to denote a constraint – behavior that is not allowed.

Document Organization

After a high-level overview, this requirements specification contains sections devoted to specific feature areas. Each section starts with an introduction of the relevant concepts and the description of the feature, followed by the associated requirements.

The presented features are in order of relevance for the Application Developers working on QP Applications, who are the primary audience of this requirements specification:


[IEEE 29148] Requirement Specification Standard, ISO/IEC/IEEE 29148:2018
[DOC-QP-SSR] Software Safety Requirements
[DOC-QP-SAS] Software Architecture Specification
[DOC-QP-SDS] Software Design Specification
[ROOM:94] Bran Selic, Garth Gullekson, Paul T. Ward: Real-Time Object-Oriented Modeling,
New York, John Wiley & Sons Inc, 1994, ISBN 978-0-471-59917-3
[PSiCC:02] Miro Samek, Practical Statecharts in C/C++, CMP Books 2002.
[PSiCC2:08] Miro Samek, Practical UML Statecharts in C/C++, 2nd Edition, Newnes 2008.
[ROOM:94] Bran Selic, Garth Gullekson, Paul T. Ward: Real-Time Object-Oriented Modeling,
New York, John Wiley & Sons Inc, 1994, ISBN 978-0-471-59917-3
[CODE2:04] Steve McConnell, Code Complete, 2nd Ed,Microsoft Press 2004.
[UML-2.5] OMG, "OMG Unified Modeling Language (OMG UML) Version 2.5.1", formal/2017-12-05, 2017
[Sutter:10] Herb Sutter, "Prefer Using Active Objects Instead of Naked Threads", Dr.Dobbs Journal, June 2010.
[Cummings:10] David M. Cummings, "Managing Concurrency in Complex Embedded Systems",
2010 Workshop on Cyber-Physical Systems.
[OOP-C:08] Quantum Leaps, Object-Oriented Programming in C,
[DbC:16] Quantum Leaps, Key Concept: Design by Contract,