工作流入门这篇就够了！

总概

定义：工作流是在计算机支持下业务流程的自动或半自动化，其通过对流程进行描述以及按一定规则执行以完成相应工作。

应用：随着计算机技术的发展以及工业生产、办公自动化等领域的需求不断提升，面向事务审批、材料提交、业务整合和数据统计等应用需求的图文工作流、业务工作流也不断涌现。利用科学工作流还可以用于研究（地理）模型的集成。

研究内容

研究工作流可从工作流模型、工作流的定义和表达、工作流引擎

1.工作流模型

1.1面向控制:通常业务工作流大多数都是面向控制的工作流，以最常见的公司请假流程为例，当请假天数小于阈值时能向主管请假，否则只能向经理审批。

1.2面向数据：通常面向数据是科学工作流处理的业务，以GIS水文分析为例，进行水文分析需要DEM数据，而且需要依次进行填挖、流向、汇流累积量等分析，通常前一步的输出结果常常为下一步的输入数据，此过程涉及到数据。因此，需选择面向数据的工作流模型。

2.工作流的定义和表达

2.1.BPMN（Business Process Modeling Notation，即业务流程建模符号）：是一种流程建模的通用和标准语言，用来绘制业务流程图，以便更好地让各部门之间理解业务流程和相互关系。

学习BPMN可去官网下载BPMN2规范文档，当然文档为全英文，需要一定英语功底

BPMN官网：BPMN Specification - Business Process Model and Notation

2.1.1BPMN结构(以上述请假案例为例)

BPMN大致可以分为两部分，一部分为<process></process>标签内，对BPMN要素的描述，另一部分为<bpmndi></bpmndi>内包含其位置信息，保证个元素的相对位置与设计时一致。

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:activiti="http://activiti.org/bpmn" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:omgdc="http://www.omg.org/spec/DD/20100524/DC" xmlns:omgdi="http://www.omg.org/spec/DD/20100524/DI" typeLanguage="http://www.w3.org/2001/XMLSchema" expressionLanguage="http://www.w3.org/1999/XPath" targetNamespace="http://www.activiti.org/test">
  <process id="leaveProcess" name="简单请假流程" isExecutable="true">
    <startEvent id="startevent1" name="Start"></startEvent>
    <userTask id="usertask1" name="请假申请"></userTask>
    <sequenceFlow id="flow1" sourceRef="startevent1" targetRef="usertask1"></sequenceFlow>
    <exclusiveGateway id="exclusivegateway1" name="Exclusive Gateway"></exclusiveGateway>
    <sequenceFlow id="flow2" sourceRef="usertask1" targetRef="exclusivegateway1"></sequenceFlow>
    <userTask id="usertask2" name="杰里奥审批"></userTask>
    <sequenceFlow id="flow3" sourceRef="exclusivegateway1" targetRef="usertask2">
      <conditionExpression xsi:type="tFormalExpression"><![CDATA[${day>0&&day<=3}]]></conditionExpression>
    </sequenceFlow>
    <userTask id="usertask3" name="汤姆逊审批"></userTask>
    <sequenceFlow id="flow4" sourceRef="exclusivegateway1" targetRef="usertask3">
      <conditionExpression xsi:type="tFormalExpression"><![CDATA[${day>3}]]></conditionExpression>
    </sequenceFlow>
    <endEvent id="endevent2" name="End"></endEvent>
    <sequenceFlow id="flow6" sourceRef="usertask3" targetRef="endevent2"></sequenceFlow>
    <sequenceFlow id="flow7" sourceRef="usertask2" targetRef="endevent2"></sequenceFlow>
  </process>
  <bpmndi:BPMNDiagram id="BPMNDiagram_leaveProcess">
    <bpmndi:BPMNPlane bpmnElement="leaveProcess" id="BPMNPlane_leaveProcess">
      <bpmndi:BPMNShape bpmnElement="startevent1" id="BPMNShape_startevent1">
        <omgdc:Bounds height="35.0" width="35.0" x="90.0" y="220.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="usertask1" id="BPMNShape_usertask1">
        <omgdc:Bounds height="55.0" width="105.0" x="280.0" y="210.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="exclusivegateway1" id="BPMNShape_exclusivegateway1">
        <omgdc:Bounds height="40.0" width="40.0" x="430.0" y="218.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="usertask2" id="BPMNShape_usertask2">
        <omgdc:Bounds height="55.0" width="105.0" x="610.0" y="70.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="usertask3" id="BPMNShape_usertask3">
        <omgdc:Bounds height="55.0" width="105.0" x="610.0" y="370.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape bpmnElement="endevent2" id="BPMNShape_endevent2">
        <omgdc:Bounds height="35.0" width="35.0" x="870.0" y="221.0"></omgdc:Bounds>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNEdge bpmnElement="flow1" id="BPMNEdge_flow1">
        <omgdi:waypoint x="125.0" y="237.0"></omgdi:waypoint>
        <omgdi:waypoint x="280.0" y="237.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow2" id="BPMNEdge_flow2">
        <omgdi:waypoint x="385.0" y="237.0"></omgdi:waypoint>
        <omgdi:waypoint x="430.0" y="238.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow3" id="BPMNEdge_flow3">
        <omgdi:waypoint x="450.0" y="218.0"></omgdi:waypoint>
        <omgdi:waypoint x="450.0" y="97.0"></omgdi:waypoint>
        <omgdi:waypoint x="610.0" y="97.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow4" id="BPMNEdge_flow4">
        <omgdi:waypoint x="450.0" y="258.0"></omgdi:waypoint>
        <omgdi:waypoint x="451.0" y="397.0"></omgdi:waypoint>
        <omgdi:waypoint x="610.0" y="397.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow6" id="BPMNEdge_flow6">
        <omgdi:waypoint x="715.0" y="397.0"></omgdi:waypoint>
        <omgdi:waypoint x="887.0" y="397.0"></omgdi:waypoint>
        <omgdi:waypoint x="887.0" y="256.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge bpmnElement="flow7" id="BPMNEdge_flow7">
        <omgdi:waypoint x="715.0" y="97.0"></omgdi:waypoint>
        <omgdi:waypoint x="887.0" y="97.0"></omgdi:waypoint>
        <omgdi:waypoint x="887.0" y="221.0"></omgdi:waypoint>
      </bpmndi:BPMNEdge>
    </bpmndi:BPMNPlane>
  </bpmndi:BPMNDiagram>
</definitions>

2.1.2 核心概念