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Software Architecture Guide

BPMN Focus on Connected Businesses

Explanation

Section titled “Explanation”

BPMN is a flowchart-like notation. Stakeholders can use it directly, and it does not depend on any implementation environment. That makes it a shared language for business and IT people (see BPMN Motivation).

Pools for each organization. A pool stands for a main participant in a process. Pools typically separate different organizations (see BPMN Swimlane (Pool and Lane)).

Message flows between pools. A message flow shows which messages cross an organizational boundary. It connects one pool to another. Each message has a single sender and a single recipient.

Message events. A message event makes a process instance wait until the right message arrives from another process. This is how one partner’s process pauses until another partner responds.

Process types. BPMN distinguishes two kinds of process:

  • Private processes are internal to one organization.
  • Public (abstract) processes show the interactions between a private process and another process or participant.

A diagram that shows several pools and the message flows between them is a collaboration (see BPMN Collaboration Diagram).

Example

Section titled “Example”

A customer orders from a webshop. The webshop asks a payment provider to charge the customer. It then asks a delivery service to ship the goods. Each of the four parties is a pool. Message flows carry the order, the payment request, the payment confirmation and the shipping request between the pools. The webshop’s process waits at a message event until the payment confirmation arrives. Each party’s own private process stays internal to that organization.

Trade-offs

Section titled “Trade-offs”

Showing only the messages between pools keeps the diagram focused on the organizational boundary. The cost is that every message needs exactly one sender and one recipient. A notice meant for several partners must be drawn as separate messages.

A customer and a webshop exchange messages across pool boundaries.

Diagram source 
<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" targetNamespace="http://example.org/bpmn">
  <collaboration id="c1">
    <participant id="pCustomer" name="Customer" processRef="customerProcess" />
    <participant id="pShop" name="Webshop" processRef="shopProcess" />
    <messageFlow id="m1" name="Order" sourceRef="placeOrder" targetRef="receiveOrder" />
    <messageFlow id="m2" name="Confirmation" sourceRef="sendConfirm" targetRef="waitConfirm" />
  </collaboration>
  <process id="customerProcess" isExecutable="false">
    <startEvent id="cs">
      <outgoing>cf1</outgoing>
    </startEvent>
    <sendTask id="placeOrder" name="Place order">
      <incoming>cf1</incoming>
      <outgoing>cf2</outgoing>
    </sendTask>
    <intermediateCatchEvent id="waitConfirm" name="Confirmation received">
      <incoming>cf2</incoming>
      <outgoing>cf3</outgoing>
      <messageEventDefinition />
    </intermediateCatchEvent>
    <endEvent id="ce">
      <incoming>cf3</incoming>
    </endEvent>
    <sequenceFlow id="cf1" sourceRef="cs" targetRef="placeOrder" />
    <sequenceFlow id="cf2" sourceRef="placeOrder" targetRef="waitConfirm" />
    <sequenceFlow id="cf3" sourceRef="waitConfirm" targetRef="ce" />
  </process>
  <process id="shopProcess" isExecutable="false">
    <startEvent id="ss" name="Order received">
      <outgoing>sf1</outgoing>
      <messageEventDefinition />
    </startEvent>
    <receiveTask id="receiveOrder" name="Receive order">
      <incoming>sf1</incoming>
      <outgoing>sf2</outgoing>
    </receiveTask>
    <sendTask id="sendConfirm" name="Send confirmation">
      <incoming>sf2</incoming>
      <outgoing>sf3</outgoing>
    </sendTask>
    <endEvent id="se">
      <incoming>sf3</incoming>
    </endEvent>
    <sequenceFlow id="sf1" sourceRef="ss" targetRef="receiveOrder" />
    <sequenceFlow id="sf2" sourceRef="receiveOrder" targetRef="sendConfirm" />
    <sequenceFlow id="sf3" sourceRef="sendConfirm" targetRef="se" />
  </process>
  <bpmndi:BPMNDiagram id="BPMNDiagram_c1">
    <bpmndi:BPMNPlane id="BPMNPlane_c1" bpmnElement="c1">
      <bpmndi:BPMNShape id="BPMNShape_pCustomer" bpmnElement="pCustomer" isHorizontal="true">
        <dc:Bounds x="112" y="80" width="618" height="160" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_pShop" bpmnElement="pShop" isHorizontal="true">
        <dc:Bounds x="80" y="320" width="682" height="160" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNEdge id="BPMNEdge_m1" bpmnElement="m1">
        <di:waypoint x="368" y="200" />
        <di:waypoint x="368" y="280" />
        <di:waypoint x="336" y="280" />
        <di:waypoint x="336" y="360" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="373" y="253" width="41" height="14" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="BPMNEdge_m2" bpmnElement="m2">
        <di:waypoint x="536" y="360" />
        <di:waypoint x="536" y="178" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="541" y="255" width="86" height="28" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNShape id="BPMNShape_cs" bpmnElement="cs">
        <dc:Bounds x="182" y="142" width="36" height="36" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_placeOrder" bpmnElement="placeOrder">
        <dc:Bounds x="318" y="120" width="100" height="80" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_waitConfirm" bpmnElement="waitConfirm">
        <dc:Bounds x="518" y="142" width="36" height="36" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="493" y="109" width="86" height="28" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_ce" bpmnElement="ce">
        <dc:Bounds x="654" y="142" width="36" height="36" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNEdge id="BPMNEdge_cf1" bpmnElement="cf1">
        <di:waypoint x="218" y="160" />
        <di:waypoint x="318" y="160" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="BPMNEdge_cf2" bpmnElement="cf2">
        <di:waypoint x="418" y="160" />
        <di:waypoint x="518" y="160" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="BPMNEdge_cf3" bpmnElement="cf3">
        <di:waypoint x="554" y="160" />
        <di:waypoint x="654" y="160" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNShape id="BPMNShape_ss" bpmnElement="ss">
        <dc:Bounds x="150" y="382" width="36" height="36" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="138" y="423" width="60" height="28" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_receiveOrder" bpmnElement="receiveOrder">
        <dc:Bounds x="286" y="360" width="100" height="80" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_sendConfirm" bpmnElement="sendConfirm">
        <dc:Bounds x="486" y="360" width="100" height="80" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="BPMNShape_se" bpmnElement="se">
        <dc:Bounds x="686" y="382" width="36" height="36" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNEdge id="BPMNEdge_sf1" bpmnElement="sf1">
        <di:waypoint x="186" y="400" />
        <di:waypoint x="286" y="400" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="BPMNEdge_sf2" bpmnElement="sf2">
        <di:waypoint x="386" y="400" />
        <di:waypoint x="486" y="400" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="BPMNEdge_sf3" bpmnElement="sf3">
        <di:waypoint x="586" y="400" />
        <di:waypoint x="686" y="400" />
      </bpmndi:BPMNEdge>
    </bpmndi:BPMNPlane>
  </bpmndi:BPMNDiagram>
</definitions>

Checks

Section titled “Checks”
  • Each participating organization in a cross-company process appears as its own pool.
  • Messages that cross organizational boundaries are drawn as message flows between pools, not inside one pool.
  • Each message has exactly one sender and one recipient.
  • Steps where a process waits for a partner’s answer use message events.
Section titled “Related”

Sources

Section titled “Sources”