Syntax

Participants

Can be specified explicitly:

sequenceDiagram
    participant Alice
    participant Bob
    Alice->>Bob: Hi Bob
    Bob->>Alice: Hi Alice
sequenceDiagram
    participant Alice
    participant Bob
    Alice->>Bob: Hi Bob
    Bob->>Alice: Hi Alice

Or implicitly:

sequenceDiagram
    Alice->>Bob: Hi Bob
    Bob->>Alice: Hi Alice
sequenceDiagram
    Alice->>Bob: Hi Bob
    Bob->>Alice: Hi Alice