Interaction use
A frame with a ref tab that stands for another interaction, spanning the lifelines it involves.
diagram sequence "Boot"
participant Bootloader as bl
participant Kernel as k
ref over bl, k : Verify signature
bl -> k : jump(entry)
Syntax
ref over <a>[, <b>]... : <name>
Specification
UML 2.5.1, 17.7.4.1 (p. 591).