The main focus of Let’s Dance is to capture interactions and their behavioural
dependencies. Elementary interactions are the building blocks by which complex
interaction rules can be defined.
An elementary interaction is a combination of a send activity model and
a receive activity model. An actor reference belonging to a role is given for
every activity model. This reference indicates which activity instances must
be performed by the same participant. Typically, there is only one participant
per role involved in a conversation. In these cases, the actor reference can be
omitted in the diagrams.
It defines an interaction
between a participant of role Seller and a participant of role Auctioning
Service. It also states that a message of type Auction creation request is sent
during the interaction.
At the right-hand side in that figure, a conditional elementary interaction
is shown. Conditional elementary interactions are valid only if the condition is
met. In the example shown, the Auctioning Service sends an Account creation
request message to the seller only if the seller is not registered.