Programming Jabber

Preface

What is Jabber? Depending on who you ask, the answer to that question could be any one (or all) of the following:

• Jabber is a technology.

• Jabber is a protocol (or set of protocols).

• Jabber is an XML-based Instant Messaging (IM) system.

• Jabber is an implementation of the set of protocols.

• Jabber is an idea whose time has come.

In fact, all these answers are right. Jabber is a set of protocols expressed within XML that allow people and applications to converse with one another. Sure, TCP sockets, STDIN/STDOUT, infrared, voice input, and teletype mechanisms all allow people and applications to converse; the difference is that Jabber provides a structured, extensible framework for exchanging all kinds of information.

This is all rather abstract, so what do we mean by “extensible framework for exchanging information”? Taking it one word at a time:

Extensible

Jabber’s substrate is XML. XML is inherently extensible in the sense that tags can be added in a hierarchical sequence. Namespaces in XML allow us to keep track of the meaning and organization of these tags.

Framework

You can put together a system for exchanging information using many different tools. The point about the “framework” is that the information exchanged and the entities that are exchanging it are contextualized, bringing meaning and structure to the interactions.

Exchanging

Conversation is two-way, and it takes many forms: question and answer, notification, compartmentalized discussion, and simple chat. ...