Use Case Methodology

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Purpose

See Requirements Analysis for a description of the role of use cases in requirements analysis.

Discussion

For discussion on various aspects of the use case methodology, go to Use case methodology discussion.

Sources

The primary source for the use cases is the OAIS reference model. Note that in the case where the diagrams and the text in the reference model report don't match, the diagrams should be taken as the authoritative representation of the OAIS model.

Organization

Use cases are clustered around the same broad categories as the OAIS Functional Entities. Like the latter, use cases are organized into hierarchy with high-level scenarios broken down into more specific tests (sub- and sub-sub-cases). To facilitate cross-references and links, each case has been assigned an alpha-numeric code: the alpha prefix designates its type (UC = use case), the number establishes its position in the hierarchy. Six main use cases have been identified in accordance with the ISO-OAIS Reference Model:

• UC-1 Ingest

• UC-2 Archival Storage

• UC-3 Data management

• UC-4 Administration

• UC-5 Preservation Planning

• UC-6 Access

PLEASE NOTE: One criticism of the ISO-OAIS is that it tends to blur the distinction between Actors and Functions. In many instances it uses the name of a function to describe an actor role. In these Use Cases the ISO-OAIS was interpreted as literally as possible which means that some actors are named with a verb/noun structure (e.g. 'Receive Submission', 'Coordinate Updates').

Use Case Template

The following template was created to capture each use case scenario:

Summary

• Number: UC-x.x.x, unique tracking number assigned to the use case.

• Name: descriptive name assigned to requirement.

• Context: links to higher-level cases, if applicable.

• Sub-Use Cases: links to lower-level cases, if applicable.

• Overview: brief description of the scenario.

• Actors: the main actor(s) involved in the scenario.

Description

• Preconditions: other use cases whose completion is a precondition for the current case.

• Trigger: the event that initiates the current case.

• Successful outcome: the outcomes of a successful resolution of the scenario.

• Steps: step-by-step breakdown describing the scenario as leading to a successful outcome.

• Exceptions: other possible variations, including unsuccessful outcomes ("Scenario B", "Scenario C" etc).

Documentation

• Citations: quotes from requirement sources explaining the need for a use case or describing one or more of its components

• Diagrams: work-flow or other diagrams illustrating the scenario.

Notes

• Notes: any additional information or issues related to the use case