I compared it to a flow chart but much more than that: it has the functionality for representing things like information moving between teams, data being stored on the cloud, and departments working in parallel on the same process. It will get you acquainted with the basic concepts, and also give you references to deeper documentation you can use if you need it. Overall, this guide will work as a standalone for the majority of uses cases startups and small businesses face. The aim was to standardize how processes were visually represented, and that aim has been carried on since by Object Management Group — a NFP technology standards consortium, snappily abbreviated as OMG.
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Write the process logic definition. Step 1: Inventory the Involved Web Services Before you can start writing the BPEL process definition, you have to become familiar with the Web services invoked from our business process. These services are called partner Web services.
Again, the Web services used in this example are fictional. Employee Travel Status Web Service. The operation will return the travel class that an employee can use, which can be economy, business, or first. See Figure 4. The Airline Web service is asynchronous; therefore, it specifies two port types: The first, FlightAvailabilityPT, is used to check the flight availability using the FlightAvailability operation. This port type specifies the FlightTicketCallback operation. The second step is therefore to define the WSDL for it.
The process has to receive messages from its clients and return results. It has to expose the TravelApprovalPT port type, which will specify an input message. It also has to declare the ClientCallbackPT port type, used to return the result to the client asynchronously, using a callback. This process is illustrated in Figure 6.
In our example, there are three different partners: the client, the employee travel status Web service, and the airline Web service.
In real-world scenarios, this may not be the case. This interaction is asynchronous. This interaction is synchronous.
Each partner link type can have one or two roles and for each role we must specify the portType it uses. For synchronous operations, there is a single role for each partner link type because the operation is only invoked in a single direction. Because it is a synchronous operation, the BPEL process waits for completion and gets a response only after the operation is completed.
For asynchronous callback operations, you have to specify two roles. The first role describes the invocation of the operation by the client.
The second role describes the invocation of a callback operation. In our example there is an asynchronous relation between the BPEL process and the airline Web service. As you already know, three partner link types are required: two specify two roles because they are asynchronous, and one specifies a single role because it is synchronous.
The first role required is the role of the travel service that is, our BPEL process. The interaction is synchronous, so we need a single role, called employeeTravelStatusService. This communication is asynchronous. Therefore we need two roles. The first role describes the participation of the airline Web service to the BPEL process, which is the airline service airlineService.
Sometimes it helps to make a diagram of all the interactions. Once the partner link types are defined, you have finished the preparation phase. Typically, a BPEL process waits for an incoming message from the client, which starts the execution of the business process. Because this invocation is synchronous, it waits for the EmployeeTravelStatusResponse message.
Each Airline Web service makes a callback, sending the TravelResponse message. The BPEL process then selects the more appropriate airline and makes a callback to the client with the TravelResponse message.
Partner Links. Next you have to define the partner links, which define different parties that interact with the BPEL process. Each partner link is related to a specific partnerLinkType that characterizes it.
Each partner link also specifies one or two attributes: myRole: Indicates the role of the business process itself. For asynchronous operations it specifies two roles. The first partner link is called client and is characterized by the travelLT tpartner link type. The client invokes the business process. You have to specify the second role: partnerRole. The second partner link is called employeeTravelStatus and is characterized by the employeeLT partner link type.
This time it is the partnerRole, because you describe the role of the Web service, which is a partner to the BPEL process. The last two partner links correspond to the airline Web services.
Because they use the same type of Web service, we specify two partner links based on a single partner link type, flightLT. Here you have asynchronous callback communication, so you need two roles.
Variables in BPEL processes are used to store, reformat, and transform messages. You usually need a variable for every message sent to the partners and received from them. In this process you need seven variables. For each variable you have to specify the type. The process main body specifies the order in which the partner Web services are invoked. Within the sequence, you first specify the input message that starts the business process.
Rather we specify the partner link, the port type, the operation name, and optionally the variable that holds the received message for consequent operations. We link the message reception with the client partner, and wait for the TravelApproval operation to be invoked on port type TravelApprovalPT. Here, the variable name is the same as the message name, but this is not necessary. Next, you need to invoke the employee travel status Web service.
Before that however we have to prepare the input for this Web service. You can construct such a message by copying the employee part of the message that is sent the client. You would write the corresponding assignment: Copy Now you can invoke the Employee Travel Status Web service. You have prepared the input message in the EmployeeTravelStatusRequest variable. Because it is a synchronous invocation, the call waits for the reply and stores it in the EmployeeTravelStatusResponse variable: Copy The next step is to invoke both airline Web services.
Again first prepare the required input message which is identical for both Web services. Therefore, write an assignment with two copy elements: Copy The input data includes the data that needs to be passed to the airline Web services. Because it is in the same format, you can pass it directly using a simple copy. In the real world, you usually need to perform a transformation.
Now you are ready to invoke both airline Web services. The two invocations differ only in the partner link name: AmericanAirlines for one and DeltaAirlines for the other. Again, you use both partner link names.
In this stage of the process, you have two ticket offers. In the next step, you have to select one. The price is inside the confirmationData message part, which is the only message part, but you still have to specify it. You also have to specify the query expression to locate the price element. Here, this is a simple XPath 1.
Otherwise copy the FlightResponseDA variable. For the callback, we use the client partner link and invoke the ClientCallback operation on the ClientCallbackPT port type. The variable that holds the reply message is TravelResponse: Copy You can see that BPEL is not very complicated and allows a relatively easy and natural specification of business processes.
The deployment process descriptor is the only part of the implementation of a process on a given platform that must be re-written to run the process on a different BPEL engine. The default filename for the process descriptor is bpel. It is recommended that you include this directory in the path for easy access. To use it you have to prepare the corresponding project file, usually called build.
You have to click the process name, fill out the following form and click on the Post XML Message button: Figure 7: BPEL Console You now get a screen notifying you that the process instance is being processed asynchronously. You can select the visual flow of the execution, instance auditing, or instance debugging. The visual flow of the instance graphically shows the execution of a BPEL process instance. For more information, see the product documentation.
Conclusion Now that you are familiar with the basic concepts of Web services composition with BPEL, you can delve more deeply into more advanced concepts. Juric holds a Ph. Resources for.
The result is that someone must shop for groceries and prepare a meal. After that, someone will eat the meal and have his or her hunger satisfied. We would say "acquire groceries," for example, not "first take care of shopping for groceries. For this reason, we use the [object] and make the [verb] passive in voice, so we write "hunger noticed. The same is true for end events, which require start events.
An activity is a step in a business process, and may be comprised of multiple elements. Elements are defined components of code that provide structure and instructions regarding the activity they embody. BPML refers to entities outside of the business process as participants. An example of a participant is an inventory system. A simple activity is a single step in a business process. A complex activity is an activity that comprises a set of steps in a business process.
A Hands-on Introduction to BPEL