What is Scribble?

Scribble is a language to describe application-level protocols among communicating systems. A protocol represents an agreement on how participating systems interact with each other. Without a protocol, it is hard to do meaningful interaction: participants simply cannot communicate effectively, since they do not know when to expect the other parties to send data, or whether the other party is ready to receive data.

However, having a description of a protocol has further benefits. It enables verification to ensure that the protocol can be implemented without resulting in unintended consequences, such as deadlocks.

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An example

module examples;

global protocol HelloWorld(role Me, role World) {
	hello(Greetings) from Me to World;
	choice at World {
		goodMorning(Compliments) from World to Me;
	} or {
		goodAfternoon(Salutations) from World to Me;
	}
}

A very simply example, but this illustrates the basic syntax for a hello world interaction, where a party performing the role Me sends a message of type Greetings to another party performing the role 'World', who subsequently makes a decision which determines which path of the choice will be followed, resulting in a GoodMorning or GoodAfternoon message being exchanged.