How is the state of a BPMN process defined?

Question

Assuming a BPMN process describing activities, gateways, start and end events. As follow:

Each step is managed by a BPMN engine. At one point, how can we tell which is the state of the process ? Activities seem to define some state embodied as actions (e.g. evaluating request). Am I correct ?

Also, if we assume activity represents the state, how do we get a listing of next possible states if we were to navigate through a dedicated follow-up application ?

Should the process be modeled in a more workflow oriented way to express those state/actions possibilities ? I have the intuition that events could also be used to manage states and possible related actions.

Answer 1

Since I am not sure what exactly you understand as state of the process, I will try to define that first. I guess you are aware of the token concept, see a discussion in the Camunda forum:

A token is a BPMN concept that represents a state within a process instance. It does not have any variables or any message.

You may now define the state of the process as a statistics how many tokens at a given time are existing, and how many are currently in a given activity or event.

This statistics can be extracted from your favorite BPMN engine (and seen e.g. in Camunda's Cockpit as little colorful bubbles). With that statistics in hand, you could in principle generate forecast on next possible states, i.e. determine scenarios how many tokens will be in the next time instance probably in each activity.

Answer 2

State has a different meaning in BPMN, it could mean: 1 - Where is the token in the flow? 2 - Is the process flow running correctly or not? 3 - Or, by a specific variable (field) in the forms. If you mean the third case, which is common in processes, you have to define a field in your data model as enum (depends on the engine) and manually or automatically change its value in the forms.

Answer 3

Obviously, the rather abstract Petri-Net-style token flow semantics of BPMN does not capture the real semantics of business processes. It has just been artificially imposed on BPMN due to academic pressure groups. A really meaningful semantics must refer to the information context of a process in the business system that owns it.

Of course, a business system that is the owner of a process (type), is, at any point during a running process, in a certain complex dynamic information state, some part of which forms the context of the process and can therefore be considered its state.

In fact, the (information) state of a process is essentially given by all the property-value slots of objects that are used or affected by (events/activities of) the process. In addition to these "global variables", the state of a process also includes

1. the values of (auxiliary) process variables,
2. the information, which activities have been started (and are ongoing).

Answer 4

Take a look into the Imixs-Workflow project. It is a event orientated workflow engine instead of the task orientated design often seen in BPM engines.

Each task in this kind of workflow engine defines a state in your process model. The workflow engine holds this state until a event is fired. An event defines the transition from one state to another.

You can find examples how to model different szenarious in a event driven workflow model here.