Architectural Viewpoint

ARCH_QP_TECH_VP

Architectural viewpoint: Programming technology and paradigms for QP/C++ Framework.

Purpose
The architectural technology Viewpoint classifies the elements of the problem and the solution around well-known software technologies and paradigms.

Architectural Views
This architectural viewpoint frames the following views:

View: Event-Driven Architecture
View: Object-Oriented Architecture
View: Application Framework

Architectural Views

The following traceable architectural views explain the applied programming technologies and paradigms:

ARCH_QP_EDA

Architectural view: Event-Driven Architecture (EDA) for QP/C++ Framework.

Description
The QP/C++ Framework component is a reusable event-driven architecture (EDA), where all interactions are triggered by events, which are delivered asynchronously and are processed without blocking.

Concerns

programming paradigm
software organization
real-time processing

Anti-Concerns
The non-blocking EDA architecture underlying the QP/C++ Framework component is in contrast to the sequential architectures, such as a traditional "shared-state concurrency with blocking" in the Real-Time Operating System (RTOS), where the application explicitly awaits events in-line in the hard-coded blocking calls to the RTOS (e.g., time-delay, semaphore, etc).

Backward Traceability

REQ_QP_NF_21: QP/C++ Framework component shall be deterministic in CPU utilization.
REQ_QP_NF_24: QP/C++ Framework component shall facilitate deterministic real-time performance analysis (such as Rate-Monotonic Scheduling/Analysis).

Forward Traceability (truncated to 2 level(s))

ARCH_QP_OOA

Architectural view: Object-Oriented (OO) paradigm for QP/C++ Framework.

Description
This architecture specification of the QP/C++ Framework component assumes an object-oriented view, utilizing the concepts such as:

encapsulation (classes)
inheritance
polymorphism
object-oriented design patterns
UML notation and semantics

These concepts are known to promote modularity, layering, and overall organization of the software.

Concerns

programming paradigm
software organization
software modularity
software interfaces
information hiding

Anti-Concerns
The object-oriented view does not restrict the choice of the programming language to only those commonly considered "object-oriented". In traditionally procedural languages, such as C, object-oriented concepts can be applied as design patterns. A set of such patterns for the C programming language is described in the reference Object-Oriented Programming in C [OO-in-C:23].

Backward Traceability

Forward Traceability (truncated to 2 level(s))

ARCH_QP_AF

Architectural view: Application framework software architecture for QP/C++ Framework component.

Description
The QP/C++ Framework component is an application framework that provides a reusable architectural substrate for a well-defined problem domain: embedded, real-time, event-driven systems. A defining property of any application framework is inversion of control, where the framework, not the application, owns the main control flow. The QP/C++ architecture incorporates this principle by orchestrating event delivery, event queuing, state machine execution, and timing services while applications supply only domain-specific behavior (the state machine specification).

This architectural view aligns naturally with the Event-Driven Architecture (ARCH_QP_EDA) and the Object-Oriented Architecture (ARCH_QP_OOA). Together, these views show how QP/C++ provides a structured, deterministic runtime that instantiates the OO abstractions and enforces the event-driven execution semantics required for safety-critical embedded systems.

Concerns
An application framework has the following key characteristics:

inversion of control: In a framework, unlike in a toolkit or a standard end-application, the overall program's flow of control is not dictated by the application, but by the framework (the framework calls the application, not the other way around).
extensibility: application developers can extend the framework by deriving and specializing the base classes provided inside the framework.
non-modifiable framework code: the framework code is not supposed to be modified, while accepting application-implemented extensions. In other words, developers can extend the framework, but cannot modify the framework.

Anti-concerns
Software organized as a framework significantly differs from software organized as a "toolkit", such as a traditional Real-Time Operating System (RTOS).

Backward Traceability

Forward Traceability (truncated to 2 level(s))

IntroductionContext Viewpoint