Information Technology Reference
In-Depth Information
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Inclusive (or OR-based) gateway
: This is a less restrictive version of the exclus-
ive gateway. It allows one or more paths to continue when diverging, depending
on conditions defined in the outgoing flows. When converging, it should wait for
all active paths to finish before continuing with a single execution path.
•
Event-based gateway
: This defines a branching point in the process where we
should wait for one of many different events before continuing with the process
execution. Event-based gateways allow the process to make a decision on which
path to follow based on the event received first.
•
Complex gateway
: This allows us to define a more complex condition, where
1
to
n
branches should be able to continue. When joining branches, we can also de-
cide whether to wait for one or more execution paths before continuing with the
next activity of the process.
Complex gateways are the only ones not supported by jBPM6. Also, for converging gate-
ways, only exclusive and parallel gateways are supported.
Connecting elements
To define the sequence between flow objects, we use sequence flows. They are represen-
ted as arrows, and the specification defines three types of sequence flows to specify differ-
ent behaviors to propagate the execution. The following diagram shows different sequence
flows:
The different sequence flows are defined as follows:
•
Uncontrolled sequence flow
: This is the most common sequence flow. It repres-
ents a connection between two flow objects, with an origin and a destination.
•
Conditional sequence flow
: This evaluates an expression to determine whether it
should continue to the next flow object or not. The expression is evaluated at
runtime when the process is being executed, usually involving a check on a pro-
cess variable.
•
Default sequence flow
: This is used in inclusive/exclusive/complex gateways. It
determines the flow that will be selected if no other path matches the specific cri-
teria.
