Handling Interactions Between Processes

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Modeling of a clinical practice guideline or care plan may require multiple processes assigned to different actor pools. Some of these processes may need to interact with others in a dynamic fashion. How are these interactions managed in an unpredictable world?

Some interactions may be relatively simple, such as a conditional process that is triggered by an event. However, others may be much more complex, requiring multiple exchanges between the interacting processes. For these situations we can make use of either orchestration or choreography.

What is Orchestration?

In an orchestra there is a conductor exerts central control, directing various musicians playing different instruments according to a composition. With process orchestration, one or more processes acts as the controller (“conductor”), directing other processes (“players”), according to some prescriptive flow (“composition”).

Orchestration is a stateful activity in that it needs to remember previous interactions, to maintain a record of the current state, and to know what still needs to be done. BPMN and CMMN are both stateful and can be used to orchestrate.

Examples of orchestration in healthcare include the execution of a care plan, chronic disease management or the management of a cancer patient by a multidisciplinary care team.

What is Choreography?

In choreography there is no central control. Interactions are more of a negotiation between participants with certain rules of engagement in place. Participants are typically acting independently, with choreography capturing the communications between the participant. In BPMN choreography involves the use of choreography tasks. A choreography task can stand alone or can be connected with other tasks into a choreography process.

Figure 1: A choreography task icon.

Examples of choreography include scheduling an examination with a patient, making a referral with a consultant, or obtaining preauthorization from an insurance company.

Comparison of Orchestration versus Choreography

Both orchestration and choreography have their pros and cons. The choice of using one or the other depends on your needs and goals.

Centralized control

Yes

No

Coupling

Tight

Loose

Complexity

Simple

Complex

Cost of maintenance

High

Low

Action

Prescriptive

Procedural contract between interacting participants

Troubleshooting

Easy, often with a single point of failure

Complex

Incorporating these into a notional model may be simple. However, actually getting them to work properly in an automated process can be challenging, especially for novices.

For healthcare a common approach is to use orchestration implemented with BPMN. These orchestrations may need to extend beyond interactions between BPMN processes and pools. They may also need to control data acquisition and connections to outside systems impacting the patient’s care, such as generative AI.

Figure 2: Orchestration in a Healthcare Solution.

Conclusion

When dealing with different processes or actor pools that need to interact, modelers use orchestration or choreography. The particular choice depends upon the conditions and the goals. Having choices allows for flexibility in designing a solution that can serve both current needs as well as evolve over time as conditions change.