System Sequence Diagrams (SSDs) Overview

Steps for Developing SSDs

• Identify input message: Analyze activity flow or diagrams to understand input messages.
• Describe the message: Describe the message from external actors using verb-noun notation.
  • Specify parameters the system needs.
• Identify special conditions: Look for iteration/loop frames, optional/alternative frames, and special conditions for input messages.
• Identify output return values: Determine return values, whether explicit on separate lines or a message's attribute.

System Sequence Diagrams (SSDs)

• Illustrate input and output events: SSDs visually represent input and output sequences for a use case scenario.
• One use-case scenario: SSDs focus on a specific scenario within a use case.
• External actor events: Diagrams depict events from external actors (generating events), their sequence, and inter-system events.
• System as black box: The system is treated as a black box, focusing on interactions rather than internal workings.
• Use case derivation: SSDs are created from use cases and often focus on successful scenarios, frequent occurrences, or complex alternatives.
• Input for object design: SSDs serve as input to object design.

System Events and Operations

• System operations: Represent the system's public interface operations triggered by external events or system events.
• High-level operations: System operations are high-level, acting as a black box.
• External actor triggers: System operations are initiated by external actors.
• Conceptual class assignment: Operations are assigned to a conceptual "System" class during behavior analysis.
• Parameter omission: In certain examples when messages have no parameters, the notation omits them. This is not always the case, though.

Explore the key steps involved in developing System Sequence Diagrams (SSDs) through a structured approach. This quiz covers identifying input messages, describing messages, and illustrating input and output events from external actors. Gain insight into how SSDs represent use case scenarios effectively.