A node may contain a GuardLang statement, which will be executed as the node's guard. The guard element has no attributes and may contain no nested elements.

With just process-definition and node a simple process definition can be built.

The simplest process definition would be a single node. Graphically, it would look like:

The corresponding XML process definition would look like:

<?xml version="1.0"?>
<process-definition
  name="simplest"
  xmlns="http://sarasvati.googlecode.com/ProcessDefinition">

  <node name="node-one" isStart="true"/>

</process-definition>

While there can be many nodes declared in a process definition, we have as yet, not defined a way of linking them together.

The following example contains three nodes.

<?xml version="1.0"?>
<process-definition
  name="example2"
  xmlns="http://sarasvati.googlecode.com/ProcessDefinition">

  <node name="node-one" isStart="true">
    <arc to="node-two"/>
    <arc to="node-three"/>
  </node>

  <node name="node-two"/>
  <node name="node-three"/>

</process-definition>

To indicate an arc, an arc element is added to the start node. The to attribute indicates the name of the target node. A node with that name must exist in the same process definition file.

Here is an example with two start nodes. They both have arcs to node-three , which uses the labelAnd join strategy. It will only execute once both node-one and node-two have completed.

<?xml version="1.0"?>
<process-definition
  name="example3"
  xmlns="http://sarasvati.googlecode.com/ProcessDefinition">

  <node name="node-one" isStart="true">
    <arc to="node-three"/>
  </node>

  <node name="node-two" isStart="true">
    <arc to="node-three"/>
  </node>

  <node name="node-three" joinType="labelAnd"/>

</process-definition>

Now that we've seen how to create links between nodes in the same process definition, let us examine how to include external process definitions and create links to them.

To examine external arcs, we'll need at least two process definitions.

This example is from the EngineConcepts section.

<?xml version="1.0"?>
<process-definition
  name="ext"
  xmlns="http://sarasvati.googlecode.com/ProcessDefinition">

  <node name="A" joinType="labelAnd">
    <arc to="B"/>
  </node>

  <node name="B" joinType="labelAnd"/>

</process-definition>

It looks like:

The graph which contains external arcs going to 'ext', is below.

<?xml version="1.0"?>
<process-definition
  name="example4"
  xmlns="http://sarasvati.googlecode.com/ProcessDefinition">

  <node name="P" isStart="true">
    <arc external="1" to="A"/>
  </node>

  <node name="Q" isStart="true">
    <arc external="2" to="A"/>
  </node>

  <node name="R" isStart="true">
    <arc external="2" to="B"/>
  </node>

  <node name="X">
    <arc to="Z"/>
  </node>

  <node name="Y">
    <arc to="Z"/>
  </node>

  <node name="Z" joinType="labelAnd"/>

  <external name="1" processDefinition="ext">
    <arc from="A" to="X"/>
  </external>

  <external name="2" processDefinition="ext">
    <arc from="B" to="Y"/>
  </external>

</process-definition>

It looks like:

When the process definition is loaded into memory, it will look like:

The process definition file format also supports custom elements and attributes, but before we discuss that, the API needs to be introduced.