Quiz Entry - updated: 2026.07.14
What kinds of actor-to-use-case connections are valid in a UC Diagram?
Any combination: one actor can drive many use cases, one use case can involve many actors, and a use case can even connect to another use case — there are no 1:1 limits.
The flexibility matters for security because a use case driven by more than one actor is a collaboration point — and showing every participating actor (not just whoever clicks the button) is what reveals the trust boundaries an attacker might cross:
Valid connection patterns:
| Pattern | Example | When to use |
|---|---|---|
| 1 actor → many UCs | User → [Login], [Search], [Checkout] | Actor has multiple capabilities |
| Many actors → 1 UC | User, Credit Card Issuer → [Online-payment] | UC requires collaboration |
| UC → UC | [Online-payment] → [Verification] | One UC triggers another |
Example combining all patterns:
User -----> [Online-payment] -----> [Verification] <----- Credit card issuer
\-----> [View History]
Key rule: Show ALL actors that participate in a UC, not just the initiator — this reveals trust boundaries for security analysis.