rule greeting.protocol {
greeting requires sender
greeting requires recipient
sender differs.from recipient
response follows request
}
docs {
The greeting.protocol rule defines the rules for valid greetings:
1. greeting requires sender: every greeting must have a sender
2. greeting requires recipient: every greeting must have a recipient
3. sender differs.from recipient: can't greet yourself
4. response follows request: responses must follow initial greetings
This demonstrates how constraints encode business rules and
protocol requirements that must always be satisfied.
}