WS-BPEL

- What is WS-BPEL?

An XML-based grammar for describing the logic to orchestrate the interaction between Web services in a business process. It defines a set of basic control structures like conditions or loops as well as elements to invoke web services and receive messages from services. It relies on WSDL to express web services interfaces. Message structures can be manipulated, assigning parts or the whole of them to variables that can in turn be used to send other messages.

- Why is it needed?

• Web services --> move towards service-oriented computing
• Applications are viewed as “services”
• Loosely coupled, dynamic interactions
• Heterogeneous platforms
• No single party has complete control
• How do you compose services in this domain?
• WSDL defined Web services have a stateless interaction model
• Messages are exchanged using
• Synchronous invocation
• Uncorrelated asynchronous invocations
• Most “real-world” business processes require a more robust interaction model
• Support for Messages exchanged in a two-way, peer-to-peer conversation lasting minutes, hours, days, etc.
• BPEL provides the ability to express stateful, long-running interactions


- Relationship with WSDL?

BPEL is layered on top of and extends the WSDL service model
• WSDL defines the specific operations allowed
• BPEL defines how WSDL operations are orchestrated to satisfy a business process
• BPEL also specifies extensions to WSDL in support of long-running asynchronous business processes
• Expressed entirely in XML
• Uses and extends WSDL 1.1
• Uses XML Schema 1.0 for the data model

- What is Apache ODE?
Apache ODE (Orchestration Director Engine) executes business processes written following the WS-BPEL standard. It talks to web services, sending and receiving messages, handling data manipulation and error recovery as described by your process definition. It supports both long and short living process executions to orchestrate all the services that are part of your application.


- References
• Real use cases scenarios