ACtE08 · Chapter 8Demo2 · Set 1🏛️ Past Licensure QuestionID: 45681d75
In a UML sequence diagram, what do the vertical dashed lines descending from participants represent?
In a UML sequence diagram, what do the vertical dashed lines descending from participants represent?
Multiple Choice Options
- A
Messages
- B✓ Correct Option
Lifeline of objects or actors
- C
Execution occurrences only
- D
System state changes
Detailed Technical Solution & Explanation
In UML sequence diagrams, the primary dimensions are:
•
Horizontal Dimension: Represents distinct participating instances (Objects, Actors, Components).
•
Vertical Dashed Lines: Represent the Lifeline of each object/actor, indicating its existence and persistence across time as interaction progresses from top to bottom.
•
Rectangular boxes placed along the lifeline represent activation bars (execution occurrences).
Option Analysis:
•
Option A (Messages): Incorrect; messages are represented by horizontal arrows connecting lifelines.
•
Option B (Lifeline of objects or actors): Correct; vertical dashed lines represent the participant's lifeline over the duration of the scenario.
•
Option C (Execution occurrences only): Incorrect; execution occurrences are indicated by thin vertical rectangular focus boxes on the lifeline.
•
Option D (System state changes): Incorrect; state changes are modeled in state machine diagrams.
Reference: Demo2 · Set 1NEC Licensure Syllabus