A python module for parsing and executing BPMN models

Supported BPMN elements so far:

Start/end events

User Task

• Form fields
  • Id, Type, Label
  • Validation, Properties
• Element Documentation

Service Task & Send Task

• Supported implementation at the moment is Connector
  • Connector Id must be http-connector
  • Input parameters needs to have following parameters:
    • url -> location of your web service, eg. http://myservice.com/api/call, and it should be String or Expression type
    • method -> http method that you will use for request, eg. GET, and it should be String or Expression type
    • url_parameter -> in case you want to send URL parameter with your request, it should be Map type with key and value. It is worth noting that value can be simple expression eg. ${my_process_variable}. Eg. URL request result for key task_id and value ${current_task}, if current_task is inside process variables, will be http://myservice.com/api/call?task_id=1
• Input variables and output variables for Service and Send task must be specified inside Input/Output tab
  • Input parameters type at the moment can be String or Expression and if you plan to use process variables you should use expression, eg. ${my_process_variable}, only String or Expression type is currently supporting expressions
    • All input variables will be send as JSON to the service
  • Output parameters will be saved to process variables by their name, String or Expression is currently advised although only Script is not supported
    • It is expected that service response with JSON
    • It will try to match Output parameter name with keys inside JSON -> if found -> process_variables[name] = response[name]

Call Activity

• CallActivity Type must be BPMN
• Called Element must be process_id of process you wish to start
• Binding must be deployment if you wish to call process from other BPMN diagram, other bindings assumes that called process is inside the same diagraas Call Activity

Gateways (Exclusive, Parallel)

Sequence flow with conditions

• To use conditions on sequence flows you must chose Condition Type Expression and in Expression you need to write key:value where key is the process variable name and value is string
• eg. standard:BPMN -> engine will check -> process_variables["standard"] == "BPMN" -> if True returns True -> process continues on that Sequence Flow
• In the future real expression will be possible

Collaboration Diagrams

• In case there is more then 1 Pool in Collaboration diagram you MUST specify in Extensions/Properties a property with name is_main and value True for your main Pool so the engine knows where to start the process

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Pending features:

• full fledged REST API
• in/out variables for Call Activity
• all standard BPMN elements
• ...

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Example BPMN model used for demo:

The package can be used as a standalone server exposing a REST API (see server.py)

Example execution trace:

Running process 1
-----------------
        [1] --> msg in: t_wrong
        [1] Waiting for user... [UserTask(Which option?)]
        [1] --> msg in: t0
        [1] DOING: UserTask(Which option?)
        [1] Waiting for user... [UserTask(Down), UserTask(Up)]
        [1] --> msg in: tup
        [1] DOING: UserTask(Up)
        [1] Waiting for user... [UserTask(Down), ParallelGateway(ParallelGateway_0vffee4)]
        [1] --> msg in: t_wrong
        [1] Waiting for user... [UserTask(Down), ParallelGateway(ParallelGateway_0vffee4)]
        [1] --> msg in: tdown
        [1] DOING: UserTask(Down)
        [1] DOING: ManualTask(Manual Task 2)
        [1] DOING: ServiceTask(Task 3)
        [1]     - checking variables={} with ['option==1']...
        [1]       DONE: Result is False
        [1]     - going down default path...
        [1] Waiting for user... [UserTask(Task down)]
        [1] --> msg in: t_wrong
        [1] Waiting for user... [UserTask(Task down)]
        [1] --> msg in: tup2
        [1] Waiting for user... [UserTask(Task down)]
        [1] --> msg in: t_wrong
        [1] Waiting for user... [UserTask(Task down)]
        [1] --> msg in: tdown2
        [1] DOING: UserTask(Task down)
        [1] DONE
Running process 2
-----------------
        [2] --> msg in: t_wrong
        [2] Waiting for user... [UserTask(Which option?)]
        [2] --> msg in: t0
        [2] DOING: UserTask(Which option?)
        [2] Waiting for user... [UserTask(Down), UserTask(Up)]
        [2] --> msg in: tup
        [2] DOING: UserTask(Up)
        [2] Waiting for user... [UserTask(Down), ParallelGateway(ParallelGateway_0vffee4)]
        [2] --> msg in: t_wrong
        [2] Waiting for user... [UserTask(Down), ParallelGateway(ParallelGateway_0vffee4)]
        [2] --> msg in: tdown
        [2] DOING: UserTask(Down)
        [2] DOING: ManualTask(Manual Task 2)
        [2] DOING: ServiceTask(Task 3)
        [2]     - checking variables={} with ['option==1']...
        [2]       DONE: Result is False
        [2]     - going down default path...
        [2] Waiting for user... [UserTask(Task down)]
        [2] --> msg in: t_wrong
        [2] Waiting for user... [UserTask(Task down)]
        [2] --> msg in: tup2
        [2] Waiting for user... [UserTask(Task down)]
        [2] --> msg in: t_wrong
        [2] Waiting for user... [UserTask(Task down)]
        [2] --> msg in: tdown2
        [2] DOING: UserTask(Task down)
        [2] DONE