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Protocols define the structure of agent-to-agent and component-to-component interactions, which in the AEA world, are in the form of communication. To learn more about interactions and interaction protocols, see here.

Protocols in the AEA world provide definitions for:

  • messages defining the structure and syntax of messages;

  • serialization defining how a message is encoded/decoded for transport; and optionally

  • dialogues defining the structure of dialogues formed from exchanging series of messages.

Protocol simplified

The framework provides a base protocol. This protocol provides a bare-bones implementation for an AEA protocol which includes a DefaultMessage class and associated DefaultSerializer and DefaultDialogue classes.

Additional protocols - i.e. a new type of interaction - can be added as packages or generated with the protocol generator.

We highly recommend you to not attempt writing your protocol manually as they tend to have involved logic; always use existing packages or the protocol generator!

Components of a protocol

A protocol package contains the following files:

  •, which defines message representation
  •, which defines the encoding and decoding logic
  • two protobuf related files

It optionally also contains

  •, which defines the structure of dialogues formed from the exchange of a series of messages
  •, which defines custom types

All protocols are for point to point interactions between two agents or agent-like services.


Each Message in an interaction protocol has a set of default fields:

  • dialogue_reference: Tuple[str, str], a reference of the dialogue the message is part of. The first part of the tuple is the reference assigned to by the agent who first initiates the dialogue (i.e. sends the first message). The second part of the tuple is the reference assigned to by the other agent. The default value is ("", "").
  • message_id: int, the identifier of the message in a dialogue. The default value is 1.
  • target: int, the id of the message this message is replying to. The default value is 0.
  • performative: Enum, the purpose/intention of the message.
  • sender: Address, the address of the sender of this message.
  • to: Address, the address of the receiver of this message.

The default values for message_id and target assume the message is the first message in a dialogue. Therefore, the message_id is set to 1 indicating the first message in the dialogue and target is 0 since the first message is the only message that does not reply to any other.

By default, the values of dialogue_reference, message_id, target are set. However, most interactions involve more than one message being sent as part of the interaction and potentially multiple simultaneous interactions utilising the same protocol. In those cases, the dialogue_reference allows different interactions to be identified as such. The message_id and target are used to keep track of messages and their replies. For instance, on receiving of a message with message_id=1 and target=0, the responding agent could respond with another with message_id=2 and target=1 replying to the first message. In particular, target holds the id of the message being replied to. This can be the preceding message, or an older one.


Each message may optionally have any number of contents of varying types.

Dialogue rules

Protocols can optionally have a dialogue module. A dialogue, respectively dialogues object, maintains the state of a single, respectively, all dialogues associated with a protocol.

The framework provides a number of helpful classes which implement most of the logic to maintain dialogues, namely the Dialogue and Dialogues base classes.

Custom protocol

The developer can generate custom protocols with the protocol generator. This lets the developer specify the speech-acts as well as optionally the dialogue structure (e.g. roles of agents participating in a dialogue, the states a dialogue may end in, and the reply structure of the speech-acts in a dialogue).

We highly recommend you do not attempt to write your own protocol code; always use existing packages or the protocol generator!