What is "di:waypoint " in BPMN?

Question

I've been reading on the XML structure of BPMN files and I have understood everything expect the use of di:waypoint . Can anyone explain me what it is used for? Here is a small xml of a bpmn file:

<?xml version="1.0" encoding="UTF-8"?> 
<definitions id="Definition">
  <process processType="Private" isExecutable="true" id="Minimal" name="Minimal Process" >

 <!-- nodes -->
    <startEvent id="_1" name="StartProcess" />
    <scriptTask id="_2" name="Hello" >
      <script>System.out.println("Hello World");</script>
    </scriptTask>
    <endEvent id="_3" name="EndProcess" >
        <terminateEventDefinition/>
    </endEvent>

    <!-- connections -->
    <sequenceFlow id="_1-_2" sourceRef="_1" targetRef="_2" />
    <sequenceFlow id="_2-_3" sourceRef="_2" targetRef="_3" />

  </process>

  <bpmndi:BPMNDiagram>
    <bpmndi:BPMNPlane bpmnElement="Minimal" >
      <bpmndi:BPMNShape bpmnElement="_1" >
        <dc:Bounds x="15" y="91" width="48" height="48" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="_2" >
        <dc:Bounds x="95" y="88" width="83" height="48" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="_3" >
        <dc:Bounds x="258" y="86" width="48" height="48" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNEdge bpmnElement="_1-_2" >
        <di:waypoint x="39" y="115" />
        <di:waypoint x="75" y="46" />
        <di:waypoint x="136" y="112" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="_2-_3" >
        <di:waypoint x="136" y="112" />
        <di:waypoint x="240" y="240" />
        <di:waypoint x="282" y="110" />
      </bpmndi:BPMNEdge>
    </bpmndi:BPMNPlane>
  </bpmndi:BPMNDiagram>

</definitions>

Answer 1

The BPMN 2.0 specification (find the pdf here: http://www.omg.org/spec/BPMN/2.0/PDF/) describes it as follows:

An edge is often depicted as a line with 2 or more points (i.e., one or more connected line segments) in the coordinate system, called waypoints. The first point typically intersects with the edge’s source, while the last point typically intersects with the edge’s target. Any points in between establish a route for the line to traverse in the diagram.

The "edges" are in your case the BPMN sequence flows in between the start event and the script task, and in between the script task and the end event.