Task: Specify Top-Level Functional Design Architecture
This task defines the top-level functions, and their interfaces, of the functional design architecture to be implemented in software.
Purpose

The purpose of this task is to define the functions of the functional design architecture, which are identified for implementation in software, and to define their interfaces.

Relationships
Main Description
The realization of the FAA on design level relies on the FDA. The Functions and the LocalDeviceManagers of the FDA represent the functionality that will eventually be application software in ECUs. The Functional Design Architecture contains Functions and LocalDeviceManagers and their connections. This task specifies the top-level structure of such Functions and their interfaces.
The top-level structure may be based on functionality, responsibility, legacy, etc. depending on engineering decisions.
To define the Functional Design Architecture, type definitions of Functions and LocalDeviceManagers necessary to realize the FAA are either defined or existing types are identified. FunctionPrototypes for each of these are then defined, and their ports are connected with Connectors.
The top-level definition of the FDA involves an adaptation of the ”ideal” abstract solution in the FAA. Adaptations are necessary to realize the same solution in the presence of resource constraints, allocation concerns, communication, hardware interfacing, sourcing, dependability, etc.
Steps
Specify top-level design functions
Specify design functions from analysis functions in the FAA that have been identified for implementation in software, according to the HW/SW assignment. The resulting specification shall after this step include top-level design functions, their external interfaces and a textual description of their behaviour and intent. The specification process involves structuring and decomposition of analysis functions to meet needs on allocation, sourcing, re-use, criticality, performance, etc.
Specify top-level local device managers
Specify local device managers to interface sensors and actuators. These participate in realizing the FunctionalDevices of the FAA.
Specify top-level hardware functions
Specify hardware functions to provide the overall behaviour of sensors, actuators and other functions to be implemented in hardware, according to the HW/SW assignment.
Specify top-level BSW functions
Specify the BSW functions needed for assessing the feasibility of the design at the design level. Implementation-specific BSW that have no impact on design level need not be defined.
Connect Function Prototypes

This step adds Connectors between ports of the interfaces of the functions in the FDA. After this step, the functional design architecture is ideally fully connected.

Identify design constraints
Design constraints that need to be posed on the overall architecture, and particularly on specific functions, are identified, assessed and documented in the dedicated work product. Such constraints could, for instance, relate to performance and limited hardware resources.
Properties
Predecessor
Multiple Occurrences
Event Driven
Ongoing
Optional
Planned
Repeatable