Transactional dialogs (t-dialogs) are like dialogs, but with only one flow of questions and responses, with no branching. Typically, they are used to perform some sort of a transaction against an API. They consist of various slots (similar to nodes) and one end-slot where the transaction is handled.
T-dialogs can be started by articles, events and dialogs.
Like with dialogs, each interaction of a user to follow the flow of such a t-dialog, is part of the t-dialog interactions.
Requests to the "ask endpoint" are treated as t-dialog interactions if they explicitly include a "tdialogstate" parameter.