Task: Prioritize System Use Cases
This task is where the system use cases are prioritized, so that their order of development can be decided and the architecturally-significant system use cases are identified and prioritized.
Discipline:  Requirements
Purpose
  • To define input to the selection of the set of system use cases and scenarios that are to be analyzed in the current iteration.
  • To define the set of  system use cases and scenarios that have a substantial architectural coverage (that exercise many architectural elements, and are, therefore, architecturally significant), from which subsystem, process and locality requirements are derived.
Relationships
Steps
Prioritize system use cases and scenarios

The System Architect (together with the Project Manager in Develop Iteration Plan) selects the system use cases (and scenarios derived from these) to be realized, and thus used to derive subsystem, process, and locality requirements. The selection of system use cases and scenarios (that are captured in the System Architecture Document as the System Use-Case View) is driven by the following:

In general the impact on architecture is correlated to the criticality. However, it must be noted that there might be critical use cases that have little or no impact, and vice versa, and some ancillary use cases can have a big impact on the architecture, which makes it questionable from a business perspective. The System Architect's main concern is to select a set of use cases that ensures broad coverage (participation) of system internals, while still satisfying other constituencies.

Document the Use-Case View

The Use-Case View is documented in the System Use-Case View section of the System Architecture Document. This section contains a listing of the significant use cases and scenarios within each package in the Use-Case Model, together with significant properties such as descriptions of the flow of events, relationships, use-case diagrams, and special requirements related to each use case.