A framework for creating instant messaging Bots that autonomously operate within an instant messaging sessions to respond to requests from other user(s) or Bot(s). Bot operation is defined by a state machine with one or more states that are described in XML documents. These XML documents abide by the grammar of a Bot Transition Definition Language (BTDL) that is defined in an XML schema. A Bot developer creates a state transition diagram via a Graphical User Interface. The state transition diagram defines states, transitions between states, and conditions for each of those state transitions and methods to be performed upon each state transition. An XML document that conforms to BTDL format is created from the state transition definition diagram. Both stateful and stateless Bots are defined using XML documents abiding to a BTDL format. A runtime environment implements the Bots, accepts runtime inputs and generates responses.