This paper presents a protocol for agents engaged in argumentation over access to information sources. Obtaining relevant information is essential for agents engaged in autonomous, goal-directed behavior, but access to such information is usually controlled by other autonomous agents having their own goals. Because these various goals may be in conflict with one another, rational interactions between the two agents may take the form of a dialog, in which requests for information are successively issued, considered, justified and criticized. Even when the agents involved in such discussions agree on all the arguments for and the arguments against granting access to some information source, they may still disagree on their preferences between these arguments.

To represent such situations, we design a protocol for dialogs between two autonomous agents for seeking and granting authorization to access some information source. This protocol is based on an argumentation dialog where agents handle specific preferences and acceptability over arguments.