South East Training - Business Process Modelling Toolkit
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Splitting and Merging Conditional Flow
The OR Gateway is used to direct flow along all paths where the conditions are met. In the example on the top left, flow will ‘always’ pass to B but only to A and C if the relevant conditions are met. A and C could represent monetary limits or levels or risk, for example.
The example on the top right is similar, but the ‘always’ or ‘unconditional’ path has been replaced by the ‘default’ or ‘otherwise’ path, indicated by the tick. Flow to B will only occur if neither of the other two conditions, A and C, is met.
Conditional Sequence Flow offers an alternative way to model the two examples given above. Instead of the OR Gateway, a diamond on the tail of the sequence flow arrow is used to indicate Conditional Sequence Flow. This can only flow from an activity, not out of an event or a gateway. The diagram on the bottom left illustrates how the situation on the top left can be modelled. The diagram on the top right, illustrating the use of the ‘default’ or ‘otherwise’ path, can be drawn in a similar way.
- The OR Gateway can be used to merge flows that are neither alternative (from an XOR Gateway) nor unconditionally parallel (from an AND split). Neither the XOR nor the AND Gateway would do the job. The OR Gateway waits for all enabled paths to complete.