BPM Notations - Gateways and Events

Using Gateways

Gateways can split your processes into multiple paths. This is because the path which the process will take at execution is based on conditions at execution. It cannot be defined while designing.

Gateways thus model all the options that the process has i.e. all the possible paths that can be taken by a process at execution. Here are the types of gateways and when to use them:

Gateway Name Symbol Implication
AND Gateway An AND gateway, helps to execute parallel tasks. It diverts the workflow on all pathways that meet into or it or come out of it. For instance consider the making of a car. There are certain tasks which can be executed in parallel and this will save time. Use an AND gateway to model such tasks in your Process model
OR Gateway An OR gateway will allow one or more routings based on certain pre-defined criteria. For instance, if your customer is taking the car along with the service contract, then the OR gateway will make both paths active.

But if the customer is taking only the service warranty or only the car, only one of the process paths will become active.

Use the OR split when you are not sure about how many paths the process will need to take from the gateway when it is executed.

XOR Gateway An XOR gateway is one which allows the process to take one and only one of the paths that come in it or go out of it. This should be done when the process will move along one of the many paths based on certain conditions.

For instance, a candidate appearing for an interview can be selected or rejected but not both. Hence use the XOR gateway and define both selection and rejection paths. Based on the input selected or rejected, the process-flow will be diverted to one but not all of the relevant paths.

BPM Notations - Events

Event Symbol Implication
Start Event The start event signals a process to start. Each process can have one and only one start event. It can be manual, automatic (timer based) or message based.
End Event An end event completes the process. A process can have multiple end events. This is denoted with a start event having a shading along its circumference.
Intermediate Event An intermediate event is any event that takes place between the start and end of the process
Message Event Message events are meant to increase the co-ordination between different processes. A message event starts a series of steps in the current process based on a message it has received from outside the process.

For instance, the purchasing process should be started after it receives a message from the store. In this case, the store is supposed to pass on information to begin a process.

The messages can be automated to ensure that the execution takes place on time and as desired.

Timer Event Timer events are useful control procedures. They initiate a series of steps automatically based on the time which has elapsed after an activity has been performed/ not performed.

The primary use of these events is to provide the customer with service levels i.e. customer can expect a repair mechanic to reach them within 24 hours.

They then notify the management is there has been no preparation to send the mechanic after let’s say 16 hours.

A single timer event can have multiple escalation paths. For example:

16-18 hours: Project Manager
18-20 hours: Delivery Manager
20-22 hours: Service Delivery Lead

Hence the escalation goes on till higher and higher levels till it gets executed. There are therefore no chances of material information being withheld since a program has been written to escalate it automatically.

Ad-Hoc Event Ad-hoc events are events which have no defined time. These are initiated by users with requisite level of access at any time within the execution of a process. Termination of a customer order is one such process. If the customer wants to cancel an order, the process must be capable of handling these events.

An ad-hoc event is initiated by an authorised user in the middle of the process to trigger a series of actions that replace the original flow of process. For instance a termination of an order starts the cancellation formalities and refund process and stops the processing of an order.

Ad-hoc events may have defined users or a group of users. This is usually the management or the supervisory level of users.

Ad-hoc events can be based on internal needs, for instance ad-hoc reports or external needs such as the one mentioned above.


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