R1810

An actual Gate on an InteractionUse must reference a formal Gate contained by the referenced Interaction.

The Message leading to/from an actual Gate of an InteractionUse must correspond to the Message leading to/from the formal Gate with the same name of the Interaction referenced by the InteractionUse.

Therefore, an actual Gate on an InteractionUse must always reference a formal Gate of the Interaction.

If you have an actual Gate on an InteractionUse which does not reference any formal Gate, you should either remove it or reference a formal Gate of the Interaction.