BPMN2

Comparisons

The Business Process Model and Notation (BPMN) defines a flowchart-based DSL for workflows. It is maintained by the Object Management Group (OMG). The latest BPMN version is 2.0.2, published in 2014.

BPMN2 defines a graphical notation to specify workflows. This notation can then be shared between tooling and organizations. The graphical notation is translated into XML, which then can be used for runtime execution.

For this comparison, we will compare the Serverless Workflow language with the graphical representation of BPMN2, and not its underlying XML representation. The BPMN2 XML is very difficult to understand, quite large for even the smallest workflows, and often not portable between runtimes. It makes more sense to use its portable graphical notation for comparisons.

Serverless Workflow is a declarative workflow language, represented with JSON or YAML. It currently does not define a graphical notation. However, it can be graphically represented using different flowcharting techniques such as UML activity diagrams. The Serverless Workflow Java SDK as well as its VSCode Extension provide means to generate SVG diagrams based on the workflow JSON/YAML.

Note when reading provided examples

The BPMN2 graphical notation does not provide details about data inputs/outputs, mapping, and transformation. BPMN2 does provide graphical representation for things such as Data Objects. However, most of the examples available do not use them. Execution semantics such as task and event properties are also not visual. For this reason, the event, function, retry, and data mapping defined in the associated Serverless Workflow YAML are assumed.

Examples

Simple File Processor

BPMN2 Diagram	Serverless Workflow
	id: processfile name: Process File Workflow version: '1.0.0' specVersion: '0.8' start: Process File states: - name: Process File type: operation actions: - functionRef: processFile end: true functions: - name: processFile operation: file://myservice.json#process

Process Application

BPMN2 Diagram

Serverless Workflow

id: processapplication name: Process Application version: '1.0.0' specVersion: '0.8' start: ProcessNewApplication states: - name: ProcessNewApplication type: event onEvents: - eventRefs: - ApplicationReceivedEvent actions: - functionRef: processApplicationFunction - functionRef: acceptApplicantFunction - functionRef: depositFeesFunction end: produceEvents: - eventRef: NotifyApplicantEvent functions: - name: processApplicationFunction operation: file://myservice.json#process - name: acceptApplicantFunction operation: file://myservice.json#accept - name: depositFeesFunction operation: file://myservice.json#deposit events: - name: ApplicationReceivedEvent type: application source: "/applications/new" - name: NotifyApplicantEvent type: notifications source: "/applicants/notify"

Compensation

BPMN2 Diagram

Serverless Workflow

id: simplecompensation name: Simple Compensation version: '1.0.0' specVersion: '0.8' start: Step 1 states: - name: Step 1 type: operation actions: - functionRef: step1function compensatedBy: Cancel Step 1 transition: Step 2 - name: Step 2 type: operation actions: - functionRef: step2function transition: OK? - name: OK? type: switch dataConditions: - name: 'yes' condition: ${ .outcome | .ok == "yes" } end: true - name: 'no' condition: ${ .outcome | .ok == "no" } end: compensate: true - name: Cancel Step 1 type: operation usedForCompensation: true actions: - functionRef: undostep1 functions: - name: step1function operation: file://myservice.json#step1 - name: step2function operation: file://myservice.json#step2 - name: undostep1function operation: file://myservice.json#undostep1

Error Handling With Retries

BPMN2 Diagram

Serverless Workflow

--- id: errorwithretries name: Error Handling With Retries Workflow version: '1.0.0' specVersion: '0.8' start: Make Coffee states: - name: Make Coffee type: operation actions: - functionRef: makeCoffee transition: Add Milk - name: Add Milk type: operation actions: - functionRef: addMilk retryRef: noMilkRetries retryableErrors: - D'oh! No more Milk! onErrors: - errorRef: D'oh! No more Milk! end: true transition: Drink Coffee - name: Drink Coffee type: operation actions: - functionRef: drinkCoffee end: true retries: - name: noMilkRetries delay: PT1M maxAttempts: 10 errors: - name: D'oh! No more Milk! code: '123' functions: - name: makeCoffee operation: file://myservice.json#make - name: addMilk operation: file://myservice.json#add - name: drinkCoffee operation: file://myservice.json#drink

Process Execution Timeout

BPMN2 Diagram

Serverless Workflow

id: executiontimeout name: Execution Timeout Workflow version: '1.0.0' specVersion: '0.8' start: Purchase Parts timeouts: workflowExecTimeout: duration: PT7D interrupt: true runBefore: Handle timeout states: - name: Purchase Parts type: operation actions: - functionRef: purchasePartsFunction transition: Unpack Parts - name: Unpack Parts type: operation actions: - functionRef: unpackPartsFunction end: true - name: Handle timeout type: operation actions: - functionRef: handleTimeoutFunction functions: - name: purchasePartsFunction operation: file://myservice.json#purchase - name: unpackPartsFunction operation: file://myservice.json#unpack - name: handleTimeoutFunction operation: file://myservice.json#handle

Multiple Instance Subprocess

BPMN2 Diagram	Serverless Workflow
	id: foreachWorkflow name: ForEach State Workflow version: '1.0.0' specVersion: '0.8' start: ForEachItem states: - name: ForEachItem type: foreach inputCollection: "${ .inputsArray }" iterationParam: "${ .inputItem }" outputCollection: "${ .outputsArray }" actions: - subFlowRef: doSomethingAndWaitForMessage end: true

• Note: We did not include the dosomethingandwaitformessage workflow in this example, which would just include a starting "operation" state transitioning to an "event" state which waits for the needed event.

Loop Subprocess

BPMN2 Diagram

Serverless Workflow

id: subflowloop name: SubFlow Loop Workflow version: '1.0.0' specVersion: '0.8' start: SubflowRepeat states: - name: SubflowRepeat type: operation actions: - functionRef: checkAndReplyToEmail actionDataFilter: fromStateData: ${ .someInput } toStateData: ${ .someInput } stateDataFilter: output: ${ .maxChecks -= 1 } transition: CheckCount - name: CheckCount type: switch dataConditions: - condition: ${ .maxChecks > 0 } transition: SubflowRepeat defaultCondition: end: true

This workflow assumes that the input to the workflow includes a maxChecks attribute set to an integer value.

• Note: We did not include the checkAndReplyToEmail workflow in this example, which would include the control-flow logic to check email and make a decision to reply to it or wait an hour.

Approve Report

BPMN2 Diagram

Serverless Workflow

id: approvereport name: Approve Report Workflow version: '1.0.0' specVersion: '0.8' start: Approve Report states: - name: Approve Report type: callback action: functionRef: managerDecideOnReport eventRef: ReportDecisionMadeEvent transition: Evaluate Report Decision - name: Evaluate Report Decision type: switch dataConditions: - name: Approve condition: "${ .decision | .approved == true }" end: true - name: Reject condition: "${ .decision | .approved != true }" transition: Update Report - name: Update Report type: callback action: functionRef: workerUpdateReport eventRef: ReportUpdatedEvent transition: Approve Report events: - name: ReportDecisionMadeEvent type: report.decisions source: reports/decision - name: ReportUpdatedEvent type: report.updated source: reports/updated functions: - name: managerDecideOnReport operation: file://myservice.json#managerapproval - name: workerUpdateReport operation: file://myservice.json#workerupdate

• Note: Human interactions during workflow execution in Serverless Workflow is handled via its Callback state.

Event Based Decision

BPMN2 Diagram

Serverless Workflow

id: eventdecision name: Event Decision workflow version: '1.0.0' specVersion: '0.8' start: A states: - name: A type: operation actions: - subFlowRef: asubflowid transition: Event Decision - name: Event Decision type: switch eventConditions: - eventRef: EventB transition: B - eventRef: EventC transition: C - name: B type: operation actions: - name: doSomething functionRef: doSomethingFunction end: true - name: C type: operation actions: - name: doSomething functionRef: doSomethingFunction end: true events: - name: EventB type: my.events.b source: "/events/+" - name: EventC type: my.events.c source: "/events/+" functions: - name: doSomethingFunction operation: file://myservice.json#dosomething