Viewpoint

SAS_QP_TECH_VP

Technology Viewpoint

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

Architectural Views
This architectural viewpoint frames the following views:

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

Views

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

SAS_QP_EDA

View: Event-Driven Architecture

Description
The QP/C++ Framework 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 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

SRS_QP_NF_21: QP/C++ Framework shall be deterministic in CPU utilization.
SRS_QP_NF_24: QP/C++ Framework shall facilitate deterministic real-time performance analysis (such as Rate-Monotonic Scheduling/Analysis).

Forward Traceability (truncated to 2 level(s))

SAS_QP_OOA

View: Object-Oriented Architecture

Description
This architecture specification of the QP/C++ Framework 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))

SAS_QP_AF

View: Application Framework

Description
QP/C++ Framework is an application framework defined as a reusable architecture for a specific problem domain (embedded, real-time systems in the case of QP/C++ Framework). The concept of an application framework works particularly well in combination with the object-oriented approach (see SAS_QP_OOA).

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 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))

Safety ViewpointContext Viewpoint