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Installation Manu al SIPLACE Engine ering Data Manag er (EDM) Version 1 .9 02/2011 Edition 49 / 65 class =" Siemens.S iplac ePro.EDM.Dat aExcha nge.Acti ons.Acq uireTempl ateListActio n,DataEx change " /> &l…
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When starting, you will first need to declare all states, events and transitions. This is necessary so that the
workflow engine operating on the configuration file can more easily verify the finite state machine.
First, we define the start state:
<state name="clientIdle" isStartState="true" />
In the following state declarations, isStartState="true" is not allowed to appear any more because a finite
state machine has exactly one start state.
A "normal" state is declared:
<state name="selectObjects" />
This state is marked as an end state:
<state name="done" isEndState="true" />
Error states are declared as follows:
<state name="timedOut" isErrorState="true" />
A state can be an error state and an end state at the same time:
<state name="failed" isErrorState="true" isEndState="true " />
The names of the states must be unique. Next, the events that the workflow engine can react to are
declared in the configuration file:
<event name="pullData" />
The names of the events also need to be unique because they are referenced in the definitions of the
transitions just like the states.
The transitions are the heart of the workflow definition. They are a kind of "building block" that can be used
to model a customer workflow.
They determine the reactions to incoming events. Every transition can execute any number of actions
when triggered by an event. To permit a certain degree of control, a transition can be equipped with a
special action that has a return value. Such actions are called controllers. In this case, the initial state,
event and result of the action are passed to the next state. An example of this is shown below:
<transition name="getTemplateList" currentState="clientIdle" event="pul lData">
<newState name="waitTemplateList">
<action
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class="Siemens.SiplacePro.EDM.DataExchange.Actions.AcquireTempl
ateListAction,DataExchange" />
<action
class="Siemens.SiplacePro.EDM.DataExchange.Actions.SendRequestA
ction,DataExchange" />
</newState>
</transition>
Figure 12 Example of a simple transition
This transition goes from the clientIdle state to the waitTemplateList state when the pullData event is
triggered. Two actions are performed during the transition, each of which is specified in the class notation
known from the application configuration. The actions are executed in the order they are listed in the file.
<transition name="selectTemplate" currentState="waitTemplateList"
event="templateList"
class="Siemens.SiplacePro.EDM.DataExchange.Actions.AskForTemplateAction,D
ataExchange">
<newState name="waitTemplate" value="OK">
<action
class="Siemens.SiplacePro.EDM.DataExchange.Actions.AcquireTempl
ateAction,DataExchange" />
<action
class="Siemens.SiplacePro.EDM.DataExchange.Actions.SendRequestA
ction,DataExchange" />
</newState>
<newState name="canceled" value="Cancel" />
</transition>
Figure 13 Example of a conditional transition
This transition performs the state transition while taking a controller into account. This special action is
specified using the attribute "class" in class notation. In this case, there is not just one "newState" tag as in
the first example in Figure 12, but instead there is one tag for each possible output of the controller. To
handle these tags, the "value" attribute is added to the "newState" tag. A controller always returns a string,
so the result can always be stored in the XML file.
To make it easier for the author of the workflow configuration to handle application cases such as the
transition for all states to valid error states like the ones arising in EDM in the form of timeouts due to the
asynchronous communication, the transitions can also be defined as shown in Figure 14:
<transition name="timeoutDefault" currentState="all" event="timeOut">
<newState name="timedOut" />
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</transition>
Figure 14 Default transition
Specifying "all" for the initial state causes this transition to be used for all states. The transition above
therefore defines a general timeout response. A default transition is only executed when no specific
transition is defined for the particular event. This means you can implicitly define more than one transition
for a state/event pair. However, it is not possible to describe more than one default transition for an event.