Task: Gather Subsystem Specification Data
This task gathers relevant information to be passed to the subsystem teams
Disciplines: System Engineering Architecture
Purpose

The purpose of this task is to colocate all the data being passed to the subsystem teams to ensure that the subsystem have a clear understanding of what they need to produce, the logical interfaces they must support, the functionality they must provide, the requirements they must meet, and the qualities of service that they must sustain.

Relationships
RolesPrimary Performer: Additional Performers:
InputsMandatory:
    Optional:
    • None
    Outputs
      Main Description

      It is expected that the organization of the model(s) used by the system engineering staff will naturally colocate much of the necessary data. However, there is usually other data - which might be stored in non-model files and tool formats - that must be provided to the subsystem teams to ensure they build the right thing. This information includes

      • Requirements allocated to the subsystem with links to requirements repositories
      • Use case, scenario, and state data defining subsystem functionality
      • Constraints and quality of service information, including parameters such as heat, weight, power, speed, and so on
      • (Logical) operational contracts including
        • function or service name
        • data pass in or out
        • pre- and post-conditions
        • quality of service constraints
      • Algorithmic and computational functionality
      • (Logical) interfaces among subsystems and between subsystems and system actors
      • Architectural structure into which the subsystem must fit

      In general, if SysML or UML is used as the primary method for capturing information, it is recommended that the system engineering model contain all this information in one package per subsystem and hand off a package to each relevant subsystem (there may be nested packages). If there is significant data external to the model, then a conformance list should provide a list of all data to be passed.

      Steps
      Create new subsystem model package within systems model
      Collect relevant pieces of the systems model

      Move the relevant specification information into the subsystem package. This typically includes:

      • (Logical) operation contracts and service specifications
      • State machines
      • Subsystem level use cases
      • Activity diagrams
      • Sequence diagrams
      • Requirements traceability links
      Review Handoff Specification Data
      Examine the specification data handed off from systems engineering to ensure that it is complete, accurate, adequate, and clear. Ensure that it meets the needs of the subsystem team as a basis on which to perform downstream Engineering and construction.
      Key Considerations

      Key considerations include:

      • Completeness
      • Accuracy
      • Ease of access by the subsystem teams
      • Clarity

      If relevant, be sure to include quality of service and dependability expectations as well.

      It is also important not to overspecify the internal structure of the subsystem, a common error. The external behavior, performance and dependability should be specified by the handoff system data but the internal structure and internal-only interfaces should not.