Usage Description

Intent

Describe solution users, their business interests and objectives (ends), and their activities (means) to achieve those objectives.

Motivation

Usage descriptions focus on the interactions between participants engaged in an exchange of information, goods, services, or some other form of value (e.g., money). There are several levels at which such interactions may be described, including:

interactions between a business and its customers, partners, or suppliers,
interactions between business managers, their peers and subordinates,
interactions between a software solution and its users, or
interactions between the components of a software solution.

Solution usage descriptions tend to focus on the interactions between a software solution user and the solution (product or service) being used.

Applicability

Use a usage description when

you discover a statement describing the usage of a software solution feature, or
you discover a statement describing a business activity that needs improvement or automation.

Considerations

Descriptions of business activities and software solution usage tend to focus on predicates and their transitive verbs (with active voice). Descriptions of solution usage may take several forms with lesser or greater levels of detail, including: feature descriptions, user stories, and use cases. For example, consider the business interactions between a loading bay clerk and a system for allocating storage space at a hazmat storage facility described as a use case, and depicted on the face card below.

Usage descriptions intend to answer the following questions:

what - what will a solution do? what is the goal of an activity? what results are achieved?
who - who are the participants engaged in the interactions needed to achieve the goal?
how - how will interactions between participants (esp. with a solution) achieve the stated activity goals?
when - when will a sequence of interactions be triggered, and what are the pre-conditions that allow it to be triggered?

Consequences

Usage descriptions often determine the overall structure (order) of the interactions between participants. Often these interaction sequences will imply a lifecycle whose states can be modeled and identified with descriptive adjectives.

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depot	accepts a delivered drum load

loading bay clerk	wants to accept a delivered drum load
depot governors	want to ensure depot safety compliance

loading bay	must be empty
delivery truck	has arrived at the loading bay

drum handler	unloads drums from a truck into the loading bay
loading bay clerk	selects drum load delivery
system	accepts a delivery manifest for a drum load
loading bay clerk	notifies the system after accepting each drum
system	assigns drum ID and prints label for each drum
loading bay clerk	notifies the system when the load is finished
system	prints delivery reports
drum handler	reloads any returned drums onto the truck