Use Case Modeling

use-case-modeling

Registry Trigger

Use when

• model use cases actors preconditions postconditions and success guarantees

Do not use when

• no task-local use case modeling decision is required

Skill Role

Define actor goal, authority, trigger, preconditions, success and alternative paths, guarantees, failure consequences, and traceability for a system interaction. Exclude persona research and detailed UI flow.

High-Value Rules

• Bound one goal and system responsibility. Name the initiating actor, affected parties, desired outcome, system boundary, included variants, and excluded goals so the use case does not become a feature catalog.
• Distinguish actor identity from authority. Record who initiates, who benefits or bears consequence, what authority is presented, and where permission is decided without treating role labels as authorization proof.
• Source triggers and preconditions. Separate external events, scheduled or system triggers, required business state, environmental assumptions, and setup performed by the use case itself.
• Describe decisions and observable outcomes, not screen choreography. Capture system responses, business branches, state transitions, and external effects while leaving layout and interaction detail to experience modeling.
• Model alternatives by consequence. Include denial, invalid input, conflict, timeout, duplicate request, partial effect, unavailable dependency, cancellation, and recovery only where reachable and material.
• State guarantees at termination. Define committed state, emitted or suppressed effects, user-visible outcome, audit or notification consequence, and what remains uncertain after success, rejection, or interruption.
• Trace claims to acceptance and ownership. Connect each material path to current rule or contract evidence, an observable acceptance oracle, and an owner for unresolved policy, data, permission, or integration behavior.

Anti-Patterns

• Substitute a click sequence, component map, or implementation flow for actor goal and system guarantee.
• Model only the successful path or collapse rejected, failed, unknown, and compensated outcomes into one error branch.
• Invent preconditions, authority, defaults, or guarantees to make the narrative complete when source evidence is missing.

Stop Conditions

Escalate when actor authority, business goal, system boundary, authoritative rule, consequential side effect, or termination guarantee is ambiguous. Also escalate when external owners cannot confirm a material path, or failure could affect money, permission, safety, regulated data, or irreversible operations.

Output Contract

• bounded use-case model with actors and authority, trigger and preconditions, decision paths, state and side effects, termination guarantees, acceptance trace, unknowns, and residual owners

Targeted References