MessageStructure

P2P Message Structure and Implementation

Introduction

This document is intended to describe the structure of the messages that are exchanged between HGDB peers.

The core attribute of a message are defined in the FIPA ACL Message Structure Specification.

The most important attribute is the performative which defines the "speech act". We attempt to follow the semantics of communication performatives which is described in the FIPA Communicative Act Library Specification

Message Structure

At the top level of any HGDB message the following attributes will be available:

Attribute name	Type	Description	Mandatory
perf	String	The name of the performative associated with the message.	YES
act	String	The name of the action. Together with Performative this defines the intent of the message (ex. "CallForProposal" for "REMEMBER" or "Accept" for "REMEMBER")	YES NO
task replyWith	UUID	Identifies the task that generated the messages. Multiple peers can receive/send messages related to the same task.	YES
conv	UUID	If the message is part of a conversation identifies the conversation.	NO
replyTo	String	A description of the end point address of the peer that is interested in an answer. This depends on the specific implementation of the transport protocol, for example, for JXTA, it could be the pipe advertisement.	NO
content	Object	This contains any additional data the destination peer needs to fulfill the intent of the message.	NO
ont	String	The ontology of the message. If not specified it defaults to the HGDB ontology, but plug-ins might be defining their own set of performatives/actions.	NO

For the JXTA end point the following attributes are available:

Attribute name	Type	Description	Mandatory
type	String	The name of the end point type. By default this is PipeAdvertisement, but other types could be used, depending on the implementation	NO
id	String	the resource identifier of the end point.	YES
name	String	the name of the end point. This is not mandatory but should be used for logging purposes.	NO

Implementations can add other attributes depending on their specific needs.