A Sent Intermediate Message is a Message that has the following additional characteristics: . Its target interactive part is an Interaction Role . . It has a previous succession . An Interactive Behavior is a kind of Behavior that can have Interactions as its Parts. To be involved in Interactions, these Parts must be sub-types of Interactive Part. A Start Message is a Message that has the following additional characteristics: . It's source interactive part is an Interaction Role . . It has a next succession to the Start Start Event instance of Event . . This Succession is an Immediate Succession. The receipt of the Start Message creates a new execution of the process. An Message Flow is a Message that has no succession to any other Message or Event Part. Such a Message doesn't have any influence on the course of its owning Interactive Behavior. A Received Intermediate Message is a Message that has the following additional characteristics: . It's source interactive part is an Interaction Role . . It has a next succession . Interactive Part is a category of Typed Part that can be connected by Interactions. The types of interactive parts establish requirements for the interacting individuals, for example, that they have a minimum security clearance or market capitalization. An End Message is a Message that has the following additional characteristics: . Its target interactive part is an Interaction Role . . It has a previous succession . . It has a next succession to the End instance of Event Part. . This Succession is an Immediate Succession . The sending the message is simultaneous with the end of the process. A Message is a kind of Simple Interaction that has an Interaction Role as one of its Interactive Parts. An Interaction Role is an Interactive Part where the individuals playing the part are in the environment context where the Behavior is used. For example, the customer is an Interaction Role in a behavior for delivering a product. An Interaction is a Behavior Step that is also a Part Connection , enabling Interaction to have start and end changes, and be ordered in time. An Interaction can be either a simple Simple Interaction or a set of combined Simple Interactions : a Compound Interaction. Ultimately, an Interaction is realized by the exchange of Simple Interactions between its Interactive Parts. A Simple Interaction is a kind of Interaction in which something is "transferred" from individuals playing one interactive part to individuals playing another interactive part. For example, a document, phone number, or package may be transferred from one department to another in a company. The transferred items must conform to a Type specified by the Simple Interaction. A Simple Interaction can have an Expression to change the item that arrives at the target based on the item flowing from the source. For example, a transformation may retrieve the zip code from an address flowing from the source to deliver the zip code to the target. Simple Interactions in user (M1) models are always typed by the Behavior Occurrence (see user library Behavior Library). This gives them the standard Event Parts, such as for start and end, so the Simple Interactions can be ordered within an Interaction Protocol. This is different from the type of thing transferred. Simple Interactions can refer to Simple Interactions inside the Interactive Parts being connected. This means the transferred thing is passed along through chains of Simple Interactions from inside to outside the parts, or the other way.