The process element defines the following child elements:

An example:

<process name="order_item" default_retries="2" default_timeout="2">
    <state name="...">
        <!-- state definition -->
    </state>
</process>

A simple process flow with security enabled:

<process name="order_item">
    <group-access>
        <group name="admin"/>
    </group-access>
    <state name="...">
        <!-- state definition -->
    </state>
</process>

No child elements are defined for group.

Affinity Elements The state element may optionally contain one affinity element. Affinity elements provide direction to where the fabric should run the state's action, allowing the state's action to execute on a fabric worker that has an application-defined resource. The following affinity elements are defined:

Action elements Following the optional affinity element, the state element must contain one action elements from the following table. The action is the activity that is run while in a given state. The action is either user code or a nested process flow.

Following the action element, the state must contain at least one arc element. The arc element is used to determine the next state of the process flow. The list of arcs is evaluated when the state action completes or is determined to have failed.

An example process flow with a single start state. Due to the single arc, this process flow will transition to finished regardless of the status or result of the state's action:

<process name="...">
    <state name="start">
        <component-action component="..." method="...">
            <!-- arguments -->
        </component-action>
        <arc status="complete" next-state="finished"/>
    </state>
</process>

The following child elements are defined. These elements describe the type of affinity to be used. Each combination affect the required signature of the affinity method (e.g., specific method signatures are required for each affinity type).

The following child elements are defined. These elements describe the type of affinity to be used. Each combination affects the required signature of the affinity method.

The following child elements are defined:

No child elements are defined.

No child elements are defined.

<process name="parent-flow">
    ...
    <state name="...">
        <sub-process name="nested-flow"/>
        <arc status="..." next-state="..." />
    </state>
    ...
</process>

The following table defines the possible values that can be returned by the fabric when executing an action:

Fabric Status Details

Details: The arc allows the application developer to control the execution of the process flow under both normal and error conditions. Error conditions detected by the fabric are reported by the fabric in the request status. By default, the process flow will arc to finished. Arcs can be added to arc to error handling states.

When the action finishes with no errors, the fabric sets status to complete. Actions that run to completion can set the result field in the request, and arcs can specify a result guard - the arc whose result matches the result in the request is taken. Note: an arc that specifies a result implies a status of complete - any other status specified in the arc is erroneous.

In the following example, process flow will transition to next-state when the action completes successfully and the action sets the result to success. If the action completes with a result set to any other value, the process flow will transition to finished. If the action is started but does not complete, the next state will be error-recovery. If the fabric is unable to execute the action, the process flow retries the current state (note: be very careful to not design infinite loops into your process flow). The flow will transition to finished if the status is in-doubt.

<process name="...">
    ...
    <state name="current-state">
        <component-action component="..." method="...">
            ...
        </component-action>
        <arc result="success" next-state="next-state"/>
        <arc status="not-completed"next-state="error-recovery"/>
        <arc status="not-attempted"next-state="current-state"/>
    </state>
    <state name="next-state">
        ...
    </state>
    <state name="error-recovery">
        ...
    </state>
    ...
</process>

No child elements are defined. The following example requires a method checkInventory defined for component my_component that takes two arguments. The method will be call passing two values from the request:

<process name="order_item">
    ...
    <state name="...">
        <component-action component="my_component" method="checkInventory">
            <arguments>
                <argument expression="request['item-id']">
                <argument expression="request['quantity']">
            </arguments>
        </component-action>
        <arc status="complete" result="..." next-state="..."/>
    </state>
    ...
</process>

No child elements are defined. In the following example, the return value of the method is being stored into the request attribute isAvailable:

<process name="order_item">
    ...
    <state name="...">
        <component-action component="my_component" method="checkInventory">
            <arguments> ... </arguments>
            <return-value expression="request['isAvailable']"/>
        </component-action>
        <arc status="..." next-state="..."/>
    </state>
    ...
</process>

No child elements are defined. In the following example, the return value is stored in attribute isAvailable and also converted to a string and stored in the action result. The process flow arcs based on the results. Note: if the action fails to complete (e.g., the method throws an unhandled exception), the process flow goes to finished because there is no arc for not-completed.

<process name="order_item">
    ...
    <state name="...">
        <component-action component="my_component" method="checkInventory">
            <arguments> ... </arguments>
            <return-value expression="request['isAvailable']"/>
            <result expression="request['isAvailable']"/>
        </component-action>
        <arc status="complete" result="true" next-state="processOrder"/>
        <arc status="complete" result="false" next-state="handleUnavailable"/>
    </state>
    ...
</process>