Object Flow   An object flow is one of two types of activity edges, which are directed connection (flows) between activity nodes, the other being a control flow. As soon as the activity node at the source (tail) end of the flow is finished it presents tokens to the object flow at the target (arrowhead) end of the flow. An object flow can only carry object (data) tokens; it cannot carry control tokens. There are rules that specify whether tokens can flow along the object flow and these are determined by the type of activity node at the source and target of the flow. In the case of complete activities an object flow may define a weight, which specifies the minimum number of tokens that must flow along the object flow as a group.

Explanation

An object flow is a like a conduit that transports object tokens through an activity. It is a directed connection and tokens can only flow in the direction of the arrow. It connects activity nodes and can thus have any one of a number of types of nodes at its tail or arrowhead end including: pins, join nodes, forks nodes, decision nodes and datastores. A number of different factors determine whether tokens will flow along the object flow. The most important factor is whether the activity node at the tail end is finished its task and presents a token to the flow. The object flow can in some circumstances be guarded and the evaluation of this guard will determine if tokens are accepted by the flow. In complete activities a weight can be specified that determines the minimum number of tokens that are required for a group and no tokens will flow until this number is reached. There is typically no delay in the transmission of object tokens by the flow, if they are accepted by the flow they are available instantaneously to the target activity node at the arrowhead end of the flow.

Important Points

An object flow can only transport object tokens.

There are two types of tokens that can flow through an activity: object and control tokens. Only object tokens can be transmitted by object flows. Control tokens are carried by control flows.

Related Entries

Action  Base Type A Flow is related to an object flow because it is the base relationship from which it is derived.

Control Flow  Sibling,  Confused with,  Graphically Similar A control flow is related to an object flow in that they are both types of activity edges. A control flow carries control tokens that coordinate the actions in an activity, whereas an object flow carries object tokens that transport data and objects in an activity.