Travel Bookings Example

Use Case

The UVW Travel Agency has a web site where customers can book any combination of air travel, hotel accommodation and car rental. The web interface allows the customer to browse flights, hotels and rental agencies, and to make their selection and pay online with a credit card, which is then approved by a Web Service invocation to a third-party agency. After credit card approval has been granted, the web application submits the booking details to a workflow management system, which attempts to make the requested bookings. If a booking attempt fails, any successful bookings must be cancelled.

Interfaces

Workflow Invocation Interface

travel(INOUT
    Bookings customerBookings)

Java Interfaces

package com.uvw.travel;

public interface Address extends java.io.Serializable {
    String getAddress1();
    String getAddress2();
    String getState();
    String getPostCode();
    String getCountry();
}

public interface Bookings extends java.io.Serializable {
    interface Booking extends Serializable {
        int ERROR = -4;
        int CARD_DECLINED = -3;
        int UNAVAILABLE = -2;
        int CANCELLED = -1;
        int PENDING = 0;
        int SUCCESS = 1;

        int getStatus();
        void setStatus(int status);
        String getCreditCardAuthorizationCode();
        void setCreditCardAuthorizationCode(String code);
        Person[] getPeople();
        Customer getCustomer();
        CreditCard getCreditCard();
    }

    interface FlightBooking extends Booking {
        Flight[] getFlights();
    }

    interface HotelBooking extends Booking {
        String getHotelName();
        Address getHotelAddress();
        Date getCheckinDate();
        Date getCheckoutDate();
    }

    interface RentalCarBooking extends Booking {
        String SMALL = "SMALL";
        String MEDIUM = "MEDIUM";
        String LARGE = "LARGE";

        String getRentalAgency();
        String getCarClass();
        Date getPickupDate();
        Date getDropoffDate();
    }

    Customer getCustomer();
    CreditCard getCreditCard();
    FlightBooking createFlightBooking(Person[] people, Flight[] flights);
    HotelBooking createHotelBooking(Person[] people, String hotelName, 
        Address hotelAddress, Date checkinDate, Date checkoutDate);
    RentalCarBooking createRentalCarBooking(Person[] people,
        String rentalAgency, String carClass, Date pickupDate,
        Date dropoffDate);
    FlightBooking getFlightBooking();
    HotelBooking getHotelBooking();
    RentalCarBooking getRentalCarBooking();
}

public interface CreditCard extends java.io.Serializable {
    String AMEX = "AMEX";
    String MC = "MASTERCARD";
    String VISA = "VISA";
    Name getCardHolder();
    String getCardType();
    String getCardNumber();
    Date getExpiryDate();
    int getSecurityDigits();
}

public interface Customer extends Person {
    String getAccountNumber();
}

public interface Flight extends java.io.Serializable {
    String getFlightNumber();
    String getFromAirportCode();
    String getToAirportCode();
    Date getDepartureTime();
    Date getArrivalTime();
}

public interface Name extends java.io.Serializable {
    String getFirstName();
    Character getMiddleInitial();
    String getLastName();
    String getFullName();
}

public interface Person extends java.io.Serializable {
    Name getName();
    Address getAddress();
}

The workflow process makes and if necessary cancels the various bookings by invoking operations from the following service interface:

package com.uvw.travel;

public interface BookingService {
    void placeBooking(Bookings.Booking booking) throws BookingException;
    void cancelBooking(Bookings.Booking booking) throws BookingException;
}

Hints

Use <xpdl:TypeDeclaration> with <xpdl:ExternalReference> to refer to the Java interfaces. Assume that the workflow engine will interpret a URI scheme of java: as the prefix to a fully qualified Java class or interface name. For example, the Bookings <xpdl:TypeDeclaration> would be defined using an <xpdl:ExternalReference> with a location attribute of java:com.uvw.travel.Bookings.
Declare an <xpdl:Application> for each of the operations in the BookingService interface, making both parameters of type IN.
Make the bookings in parallel, but remember that any combination of bookings can be made. Provide paths that conditionally bypass each of the booking types, to ensure that the parallel threads can join up again.
Use JavaScript (application/javascript) to access the booking fields.

Questions

Why is it necessary to use IN parameters? XPDL requires pass-by-value semantics for such parameters, but this is impractical when an expression yields a non-primitive type – why? OBE uses pass-by-reference for complex parameter values.
What would happen if you tried to use INOUT to force XPDL copy-restore style semantics?

Solution

Process Model Description

The workflow is triggered by the TravelBookingReceived event (defined in $OBE_HOME/examples/config/BasicApplicationEvent.xml). Notice the <xpdl:ExtendedAttribute name="obe.Event"> element attached to the <WorkflowProcess> below: see how it initializes the mandatory¹ custBookings process attribute from the event by specifying it as an OUT parameter of the event.
Route Activity a1 serves to initiate the appropriate bookings via transitions (t1, t3, t4) bearing guard conditions that only fire if the Bookings object contains a Booking of the appropriate type.

The 'Book Flight' activity is activated by transition t1 if a FlightBooking has been requested. The activity invokes the placeBooking() procedure, passing the custBookings.flightBooking object.
The 'Book Hotel' activity is activated by transition t3 if a HotelBooking has been requested. The activity invokes the placeBooking() procedure, passing the custBookings.hotelBooking object.
The 'Book Rental Car' activity is activated by transition t4 if a RentalCarBooking has been requested. The activity invokes the placeBooking() procedure, passing the custBookings.rentalCarBooking object.

Transitions (t27, t28, t29) respectively bear the inverse guard conditions and provide alternative workflow paths in the 'booking type not requested' cases.
Route activity a5 has an AND-join that is satisfied only once all inbound transitions (t33, t34, t35) have fired. This is the reason why it was necessary to provide the aforementioned alternative paths - to ensure that activity a5 starts regardless of which booking types have been requested.
Transition t15 linking activity a5 to activity a6 only fires if all requested booking types were made successfully.
If any booking failed, the OTHERWISE transition t16 fires instead, activating the appropriate compensating transactions in activities 'Cancel Flight', 'Cancel Hotel' and 'Cancel Rental Car', each of which calls the cancelBooking() procedure. Note that each of these compensating activities also has a bypass transition ( t18, t19, t20) with the inverse conditions, to ensure that transitions (t24, t25, t26) always fire regardless of which bookings had to be cancelled.
Route activity a6 has an XOR join that is fired by either transition t15 (success path) or t17 (failure path). It auto-completes immediately thereby resulting in the completion of the workflow process.

XPDL Process Model

<?xml version="1.0" encoding="UTF-8"?>
<Package Id="travel-booking" Name="UVW Travel Agency" xmlns="http://www.wfmc.org/2002/XPDL1.0"
    xmlns:xpdl="http://www.wfmc.org/2002/XPDL1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.wfmc.org/2002/XPDL1.0 http://wfmc.org/standards/docs/TC-1025_schema_10_xpdl.xsd">
    <PackageHeader>
        <XPDLVersion>1.0</XPDLVersion>
        <Vendor>Open Business Engine</Vendor>
        <Created>2004-08-08 22:32:06</Created>
    </PackageHeader>
    <RedefinableHeader PublicationStatus="UNDER_TEST"/>
    <ConformanceClass GraphConformance="NON_BLOCKED"/>
    <Script Type="application/javascript" Version="1.0"/>
    <TypeDeclarations>
        <TypeDeclaration Id="Customer">
            <ExternalReference location="java:com.uvw.travel.Customer"/>
        </TypeDeclaration>
        <TypeDeclaration Id="Address">
            <ExternalReference location="java:com.uvw.travel.Address"/>
            <Description>A generic address object.</Description>
        </TypeDeclaration>
        <TypeDeclaration Id="CreditCard" Name="Credit Card">
            <ExternalReference location="java:com.uvw.travel.CreditCard"/>
        </TypeDeclaration>
        <TypeDeclaration Id="Flight">
            <ExternalReference location="java:com.uvw.travel.Flight"/>
        </TypeDeclaration>
        <TypeDeclaration Id="Bookings" Name="Customer Bookings">
            <ExternalReference location="java:com.uvw.travel.Bookings"/>
            <Description>Bookings to make for a customer.</Description>
        </TypeDeclaration>
        <TypeDeclaration Id="Booking">
            <ExternalReference location="java:com.uvw.travel.Bookings$Booking"/>
        </TypeDeclaration>
        <TypeDeclaration Id="FlightBooking" Name="Flight Booking">
            <ExternalReference location="java:com.uvw.travel.Bookings$FlightBooking"/>
        </TypeDeclaration>
        <TypeDeclaration Id="HotelBooking" Name="Hotel Booking">
            <ExternalReference location="java:com.uvw.travel.Bookings$HotelBooking"/>
        </TypeDeclaration>
        <TypeDeclaration Id="RentalCarBooking" Name="Rental Car Booking">
            <ExternalReference location="java:com.uvw.travel.Bookings$RentalCarBooking"/>
        </TypeDeclaration>
    </TypeDeclarations>
    <WorkflowProcesses>
        <WorkflowProcess AccessLevel="PUBLIC" Id="travel-booking" Name="Travel Booking">
            <ProcessHeader DurationUnit="D">
                <Created>2004-08-08 22:33:02</Created>
                <Description>Coordinates multiple travel-related bookings.</Description>
            </ProcessHeader>
            <RedefinableHeader PublicationStatus="UNDER_TEST">
                <Author>Adrian Price</Author>
            </RedefinableHeader>
            <FormalParameters>
                <FormalParameter Id="custBookings" Mode="IN">
                    <DataType>
                        <DeclaredType Id="Bookings"/>
                    </DataType>
                    <Description>These are the bookings the customer wishes to make.</Description>
                </FormalParameter>
            </FormalParameters>
            <Applications>
                <Application Id="createBooking" Name="Create a booking">
                    <Description>Creates a booking.</Description>
                    <FormalParameters>
                        <FormalParameter Id="creditCard" Mode="IN">
                            <DataType>
                                <DeclaredType Id="CreditCard"/>
                            </DataType>
                            <Description>The credit card to charge for the booking.</Description>
                        </FormalParameter>
                        <FormalParameter Id="booking" Mode="IN">
                            <DataType>
                                <DeclaredType Id="Booking"/>
                            </DataType>
                            <Description>The booking to make.</Description>
                        </FormalParameter>
                    </FormalParameters>
                </Application>
                <Application Id="cancelBooking" Name="Cancel a Booking">
                    <Description>Cancels a previous booking.</Description>
                    <FormalParameters>
                        <FormalParameter Id="creditCard" Mode="IN">
                            <DataType>
                                <DeclaredType Id="CreditCard"/>
                            </DataType>
                            <Description>The credit card to refund.</Description>
                        </FormalParameter>
                        <FormalParameter Id="booking" Mode="IN">
                            <DataType>
                                <DeclaredType Id="Booking"/>
                            </DataType>
                            <Description>The booking to cancel.</Description>
                        </FormalParameter>
                    </FormalParameters>
                </Application>
            </Applications>
            <Activities>
                <Activity Id="a1">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Split Type="AND">
                                <TransitionRefs>
                                    <TransitionRef Id="t3"/>
                                    <TransitionRef Id="t29"/>
                                    <TransitionRef Id="t28"/>
                                    <TransitionRef Id="t27"/>
                                    <TransitionRef Id="t4"/>
                                    <TransitionRef Id="t1"/>
                                </TransitionRefs>
                            </Split>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="140"/>
                        <ExtendedAttribute Name="YOffset" Value="130"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="book-flight" Name="Book Flight">
                    <Implementation>
                        <Tool Id="createBooking" Type="PROCEDURE">
                            <ActualParameters>
                                <ActualParameter>custBookings.creditCard</ActualParameter>
                                <ActualParameter>custBookings.bookings.flightBooking</ActualParameter>
                            </ActualParameters>
                        </Tool>
                    </Implementation>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="280"/>
                        <ExtendedAttribute Name="YOffset" Value="10"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="book-hotel" Name="Book Hotel">
                    <Implementation>
                        <Tool Id="createBooking" Type="PROCEDURE">
                            <ActualParameters>
                                <ActualParameter>custBookings.creditCard</ActualParameter>
                                <ActualParameter>custBookings.bookings.hotelBooking</ActualParameter>
                            </ActualParameters>
                        </Tool>
                    </Implementation>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="280"/>
                        <ExtendedAttribute Name="YOffset" Value="130"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="book-rental-car" Name="Book Rental Car">
                    <Implementation>
                        <Tool Id="createBooking" Type="PROCEDURE">
                            <ActualParameters>
                                <ActualParameter>custBookings.creditCard</ActualParameter>
                                <ActualParameter>custBookings.bookings.rentalCarBooking</ActualParameter>
                            </ActualParameters>
                        </Tool>
                    </Implementation>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="280"/>
                        <ExtendedAttribute Name="YOffset" Value="250"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a5">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="AND"/>
                            <Split Type="XOR">
                                <TransitionRefs>
                                    <TransitionRef Id="t16"/>
                                    <TransitionRef Id="t15"/>
                                </TransitionRefs>
                            </Split>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="430"/>
                        <ExtendedAttribute Name="YOffset" Value="190"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a6">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="900"/>
                        <ExtendedAttribute Name="YOffset" Value="190"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="cancel-flight" Name="Cancel Flight">
                    <Implementation>
                        <Tool Id="cancelBooking" Type="PROCEDURE">
                            <ActualParameters>
                                <ActualParameter>custBookings.creditCard</ActualParameter>
                                <ActualParameter>custBookings.bookings.flightBooking</ActualParameter>
                            </ActualParameters>
                        </Tool>
                    </Implementation>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="640"/>
                        <ExtendedAttribute Name="YOffset" Value="230"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="cancel-hotel" Name="Cancel Hotel">
                    <Implementation>
                        <Tool Id="cancelBooking" Type="PROCEDURE">
                            <ActualParameters>
                                <ActualParameter>custBookings.creditCard</ActualParameter>
                                <ActualParameter>custBookings.bookings.hotelBooking</ActualParameter>
                            </ActualParameters>
                        </Tool>
                    </Implementation>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="640"/>
                        <ExtendedAttribute Name="YOffset" Value="350"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="cancel-rental-car" Name="Cancel Rental Car">
                    <Implementation>
                        <Tool Id="cancelBooking" Type="PROCEDURE">
                            <ActualParameters>
                                <ActualParameter>custBookings.creditCard</ActualParameter>
                                <ActualParameter>custBookings.bookings.rentalCarBooking</ActualParameter>
                            </ActualParameters>
                        </Tool>
                    </Implementation>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="640"/>
                        <ExtendedAttribute Name="YOffset" Value="470"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a10">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Split Type="AND">
                                <TransitionRefs>
                                    <TransitionRef Id="t19"/>
                                    <TransitionRef Id="t11"/>
                                    <TransitionRef Id="t20"/>
                                    <TransitionRef Id="t18"/>
                                    <TransitionRef Id="t10"/>
                                    <TransitionRef Id="t9"/>
                                </TransitionRefs>
                            </Split>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="490"/>
                        <ExtendedAttribute Name="YOffset" Value="350"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a11">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="AND"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="790"/>
                        <ExtendedAttribute Name="YOffset" Value="410"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a12">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="640"/>
                        <ExtendedAttribute Name="YOffset" Value="290"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a13">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="640"/>
                        <ExtendedAttribute Name="YOffset" Value="410"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a14">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="640"/>
                        <ExtendedAttribute Name="YOffset" Value="530"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a15">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="280"/>
                        <ExtendedAttribute Name="YOffset" Value="70"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a16">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="280"/>
                        <ExtendedAttribute Name="YOffset" Value="190"/>
                    </ExtendedAttributes>
                </Activity>
                <Activity Id="a17">
                    <Route/>
                    <StartMode>
                        <Automatic/>
                    </StartMode>
                    <FinishMode>
                        <Automatic/>
                    </FinishMode>
                    <TransitionRestrictions>
                        <TransitionRestriction>
                            <Join Type="XOR"/>
                        </TransitionRestriction>
                    </TransitionRestrictions>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="ParticipantID" Value="FreeTextExpressionParticipant"/>
                        <ExtendedAttribute Name="XOffset" Value="280"/>
                        <ExtendedAttribute Name="YOffset" Value="310"/>
                    </ExtendedAttributes>
                </Activity>
            </Activities>
            <Transitions>
                <Transition From="a1" Id="t1" To="book-flight">
                    <Condition Type="CONDITION">custBookings.flightBooking != null</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a1" Id="t3" To="book-hotel">
                    <Condition Type="CONDITION">custBookings.hotelBooking != null</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a1" Id="t4" To="book-rental-car">
                    <Condition Type="CONDITION">custBookings.rentalCarBooking != null</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a10" Id="t9" To="cancel-flight">
                    <Condition Type="CONDITION">custBookings.flightBooking != null &amp;&amp; custBookings.flightBooking.status = 1</Condition>
                    <Description>If we succeeded in booking a flight, cancel it.</Description>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a10" Id="t10" To="cancel-hotel">
                    <Condition Type="CONDITION">custBookings.hotelBooking != null &amp;&amp; custBookings.hotelBooking.status = 1</Condition>
                    <Description>If we succeeded in booking an hotel, cancel it.</Description>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a10" Id="t11" To="cancel-rental-car">
                    <Condition Type="CONDITION">custBookings.rentalCarBooking != null &amp;&amp; custBookings.rentalCarBooking.status = 1</Condition>
                    <Description>If we succeeded in booking a rental car, cancel it.</Description>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a5" Id="t15" To="a6">
                    <Condition Type="CONDITION">custBookings.flightBooking == null || custBookings.flightBooking.status = 1 &amp;&amp; custBookings.hotelBooking == null || custBookings.hotelBooking.status = 1 &amp;&amp; custBookings.rentalCarBooking == null || custBookings.rentalCarBooking.status = 1</Condition>
                    <Description>If all required bookings succeeded, proceed.</Description>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a5" Id="t16" To="a10">
                    <Condition Type="OTHERWISE"/>
                    <Description>Otherwise, cancel any bookings that succeeded.</Description>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a11" Id="t17" To="a6">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a10" Id="t18" Name="Transition" To="a12">
                    <Condition Type="CONDITION">custBookings.flightBooking == null || custBookings.flightBooking.status != 1</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a10" Id="t19" To="a13">
                    <Condition Type="CONDITION">custBookings.hotelBooking == null || custBookings.hotelBooking.status != 1</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a10" Id="t20" To="a14">
                    <Condition Type="CONDITION">custBookings.rentalCarBooking == null || custBookings.rentalCarBooking.status != 1</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="cancel-flight" Id="t21" To="a12">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="cancel-hotel" Id="t22" To="a13">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="cancel-rental-car" Id="t23" To="a14">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a12" Id="t24" To="a11">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a13" Id="t25" To="a11">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a14" Id="t26" To="a11">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a1" Id="t27" To="a15">
                    <Condition Type="CONDITION">custBookings.flightBooking == null</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a1" Id="t28" To="a16">
                    <Condition Type="CONDITION">custBookings.hotelBooking == null</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a1" Id="t29" To="a17">
                    <Condition Type="CONDITION">custBookings.rentalCarBooking == null</Condition>
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="book-flight" Id="t30" To="a15">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="book-hotel" Id="t31" To="a16">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="book-rental-car" Id="t32" To="a17">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a15" Id="t33" To="a5">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a16" Id="t34" To="a5">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
                <Transition From="a17" Id="t35" To="a5">
                    <ExtendedAttributes>
                        <ExtendedAttribute Name="RoutingType" Value="NOROUTING"/>
                    </ExtendedAttributes>
                </Transition>
            </Transitions>
            <ExtendedAttributes>
                <ExtendedAttribute Name="obe.Event">
                    <obe:Event Id="TravelBookingReceived">
                        <xpdl:ActualParameters>
                            <xpdl:ActualParameter>custBookings</xpdl:ActualParameter>
                        </xpdl:ActualParameters>
                    </obe:Event>
                </ExtendedAttribute>
                <ExtendedAttribute Name="StartOfWorkflow" Value="FreeTextExpressionParticipant;a1;60;130;NOROUTING"/>
                <ExtendedAttribute Name="EndOfWorkflow" Value="FreeTextExpressionParticipant;a6;1020;190;NOROUTING"/>
                <ExtendedAttribute Name="ParticipantVisualOrder" Value="FreeTextExpressionParticipant;"/>
            </ExtendedAttributes>
        </WorkflowProcess>
    </WorkflowProcesses>
    <ExtendedAttributes>
        <ExtendedAttribute Name="MadeBy" Value="JaWE"/>
        <ExtendedAttribute Name="Version" Value="1.2"/>
    </ExtendedAttributes>
</Package>

Solution Files

See the solution files under $OBE_HOME/examples:

config/processes/travel-booking.xpdl
config/BasicToolAgentFactory.xml
etc/TravelBooking/bookings.ser
src/com/uvw/travel/Address.java
src/com/uvw/travel/BookingException.java
src/com/uvw/travel/Bookings.java
src/com/uvw/travel/BookingService.java
src/com/uvw/travel/CreditCard.java
src/com/uvw/travel/Flight.java
src/com/uvw/travel/Name.java
src/com/uvw/travel/Person.java
src/com/uvw/travel/impl/AddressImpl.java
src/com/uvw/travel/impl/BookingServiceImpl.java
src/com/uvw/travel/impl/BookingsImpl.java
src/com/uvw/travel/impl/CreditCardImpl.java
src/com/uvw/travel/impl/CustomerImpl.java
src/com/uvw/travel/impl/FlightImpl.java
src/com/uvw/travel/impl/NameImpl.java
src/com/uvw/travel/impl/PersonImpl.java

Deployment and Execution

This particular workflow process cannot be manually started; instead, it must be triggered by the TravelBookingReceived application event. Such an event contains a Java object which implements the


    com.uvw.travel.Bookings

interface.

Deploy the travel-booking .xpdl package.
Open a console window and navigate to the $OBE_HOME/examples/etc/TravelBooking directory.
Start a workflow instance by executing the command:

jmsclient -f bookings.ser -t object send queue/org/obe/jms/ApplicationEventQueue

You can enable logging to observe in-flight process activity, or use a worklist client or the cladmin tool to probe process instances.
The test data in bookings.ser were produced by the com.uvw.travel.test.TravelBookingTest program. You may wish to edit the source to change the data in order to experiment with different paths through the workflow.

¹ Mandatory, because the

custBookings

attribute appears as a <FormalParameter> of the <WorkflowProcess>, meaning that it must be assigned a value before a newly created process instance can be started.