Table 10.83 – ThrowEvent attributes and model associations
eventDefinitions: EventDefinition [0..*] |
Defines the event EventDefinitions that are results expected for |
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a throw Event. These EventDefinitions are only valid inside the |
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current Event. |
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• If there is no EventDefinition defined, this is considered a throw |
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None Event and the Event will not have an Internal marker (see |
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Figure 10.91 ). |
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• If there is more than one EventDefinition defined, this is |
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considered a throw Multiple Event and the Event will have the |
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pentagon internal marker (see Figure 10.90 ). |
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This is an ordered set. |
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dataInputAssociations: DataInput |
The Data Associations of the throw Event. |
Association [0..*] |
The dataInputAssociation of a throw Event is responsible for the |
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assignment of a data element that is in scope of the Event to the |
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Event data. |
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For a throw Multiple Event, multiple Data Associations might be |
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REQUIRED, depending on the individual results of the Event. |
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dataInputs: DataInput [0..*] |
The Data Inputs for the throw Event. This is an ordered set. |
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inputSet: InputSet [0..1] |
The InputSet for the throw Event. |
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Implicit Throw Event
A sub-type of throw Event is the ImplicitThrowEvent. This is a non-graphical Event that is used for MultiInstance Activities (see page 190). The ImplicitThrowEvent element inherits the attributes and model associations of ThrowEvent (see Table 10.84), but does not have any additional attributes or model associations.
10.5.2 Start Event
As the name implies, the Start Event indicates where a particular Process will start. In terms of Sequence Flows, the Start Event starts the flow of the Process, and thus, will not have any incoming Sequence Flows—no Sequence Flow can connect to a Start Event.
The Start Event shares the same basic shape of the Intermediate Event and End Event, a circle with an open center so that markers can be placed within the circle to indicate variations of the Event.
A Start Event is a circle that MUST be drawn with a single thin line (see Figure 10.70).
The use of text, color, size, and lines for a Start Event MUST follow the rules defined in “Use of Text, Color, Size, and Lines in a Diagram” on page 39 with the exception that:
The thickness of the line MUST remain thin so that the Start Event can be distinguished from the
Intermediate and End Events.
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Figure 10.70 – Start Event
Throughout this document, we discuss how Sequence Flows are used within a Process. To facilitate this discussion, we employ the concept of a token that will traverse the Sequence Flows and pass through the elements in the Process. A token is a theoretical concept that is used as an aid to define the behavior of a Process that is being performed. The behavior of Process elements can be defined by describing how they interact with a token as it “traverses” the structure of the Process.
NOTE: A token does not traverse a Message Flow since it is a Message that is passed down a Message Flow (as the name implies).
Semantics of the Start Event include:
A Start Event is OPTIONAL: a Process level—a top-level Process, a Sub-Process (embedded), or a Global Process (called Process)—MAY (is NOT REQUIRED to) have a Start Event.
NOTE: A Process MAY have more than one Process level (i.e., it can include Expanded Sub-Processes or Call Activities that call other Processes). The use of Start and End Events is independent for each level of the Diagram.
If a Process is complex and/or the starting conditions are not obvious, then it is RECOMMENDED that a Start Event be used.
If a Start Event is not used, then the implicit Start Event for the Process SHALL NOT have a trigger. If there is an End Event, then there MUST be at least one Start Event.
All Flow Objects that do not have an incoming Sequence Flow (i.e., are not a target of a Sequence Flow) SHALL be instantiated when the Process is instantiated.
Exceptions to this are Activities that are defined as being Compensation Activities (it has the Compensation marker). Compensation Activities are not considered a part of the normal flow and MUST NOT be instantiated when the Process is instantiated. See page 301 for more information on Compensation Activities.
An exception to this is a catching Link Intermediate Event, which is not allowed to have incoming
Sequence Flows. See page 266 for more information on Link Intermediate Events.
An exception to this is an Event Sub-Process, which is not allowed to have incoming Sequence Flows and will only be instantiated when its Start Event is triggered. See page 174 for more information on Event Sub-Processes.
There MAY be multiple Start Events for a given Process level.
Each Start Event is an independent Event. That is, a Process instance SHALL be generated when the Start Event is triggered.
If the Process is used as a global Process (a callable Process that can be invoked from Call Activities of other Processes) and there are multiple None Start Events, then when flow is transferred from the parent Process to the global Process, only one of the global Process’s Start Events will be triggered. The targetRef attribute of a Sequence Flow incoming to the Call Activity object can be extended to identify the appropriate Start Event.
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NOTE: The behavior of Process can be harder to understand if there are multiple Start Events. It is RECOMMENDED that this feature be used sparingly and that the modeler be aware that other readers of the Diagram could have difficulty understanding the intent of the Diagram.
When the trigger for a Start Event occurs, a new Process will be instantiated and a token will be generated for each outgoing Sequence Flow from that Event.
Start Event Triggers
Start Events can be used for these types of Processes:
•Top-level Processes
•Sub-Processes (embedded)
•Global Process (called)
•Event Sub-Processes
The next three sub clauses describe the types of Start Events that can be used for each of these three types of
Processes.
Start Events for Top-level Processes
There are many ways that top-level Processes can be started (instantiated). The trigger for a Start Event is designed to show the general mechanisms that will instantiate that particular Process. There are seven (7) types of Start Events for top-level Processes in BPMN (see Table 10.84): None, Message, Timer, Conditional, Signal, Multiple, and Parallel.
A top-level Process that has at least one None Start Event MAY be called by a Call Activity in another Process. The None Start Event is used for invoking the Process from the Call Activity. All other types of Start Events are only applicable when the Process is used as a top-level Process.
Table 10.84 – Top-Level Process Start Event Types
Trigger |
Description |
Marker |
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None |
The None Start Event does not have a defined trigger. There is no |
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specific EventDefinition subclass (see page 259) for None Start |
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Events. If the Start Event has no associated EventDefinition, then |
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the Event MUST be displayed without a marker (see the figure on the |
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right). |
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Message |
A Message arrives from a Participant and triggers the start of the |
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Process. See page 91 for more details on Messages. |
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If there is only one EventDefinition associated with the Start Event |
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and that EventDefinition is of the subclass |
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MessageEventDefinition, then the Event is a Message Start Event |
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and MUST be displayed with an envelope marker (see the figure to the |
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right). |
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The actual Participant from which the Message is received can be |
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identified by connecting the Event to a Participant using a Message Flow |
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within the definitional Collaboration of the Process – see Table 10.1. |
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