Because of the need to devise systems for electronic communication on the internet, multi-agent computing is moving to a model of communication as a structured conversation between rational agents. For example, in multi-agent systems, an electronic agent searches around the internet, and collects certain kinds of information by asking questions to other agents. Such agents also reason with each other when they engage in negotiation and persuasion. It is shown in this book that critical argumentation is best represented in this framework by the model of reasoned argument called a dialog, in which two or more parties engage in a polite and orderly exchange with each other according to rules governed by conversation policies. In such dialog argumentation, the two parties reason together by taking turns asking questions, offering replies, and offering reasons to support a claim. They try to settle their disagreements by an orderly conversational exchange that is partly adversarial and partly collaborative.