Web Service Composition Prepared by Robert Ma February 5, 2007

ECE 1770 –Web Service Composition Web Services Consider the following set of web services

ECE 1770 –Web Service Composition Web Services (2) What about between organizations?

ECE 1770 –Web Service Composition Overview Businesses today requires to quickly adapt to customer needs and market conditions EAI and B2B interactions (through web services) Needs to be flexible internally and externally Without a common set of standard, each organization is left to build their own set of proprietary business protocols Leaving little flexibility for true web services collaboration

ECE 1770 –Web Service Composition Web Service Composition Definition: Provides an open, standards-based approach for connecting web services together to create higher-level business processes. Standards are designed to reduce the complexity required to compose web services, hence reducing time and costs, and increase overall efficiency in businesses

ECE 1770 –Web Service Composition Web Service Composition (2)

ECE 1770 –Web Service Composition Basic Requirements Ability to invoke services in a asynchronous manner Achieve reliability, scalability, and adaptability required by Todays IT environment Manage exception and transactional integrity Studies shown nearly 80% of the time spent in building business processes are spent in exception management Provide dynamic, flexible, and adaptable framework Provide a clear separation between the process logic and the web services used Able to compose higher-level services from existing processes

ECE 1770 –Web Service Composition Standards BPEL4WS (a.k.a. BPEL) – Business Process Execution Language for Web Services IBM and Microsoft WSCI – Web Services Choreography Interface Sun, SAP, BEA, and Intalio BPML – Business Process Management Language BPMI.org (chartered by Intarlio, Sterling Commerce, Sun, CSC, and others)

ECE 1770 –Web Service Composition BPEL4WS XML-Based language It describes the control logic for web services coordination in a business process Interpreted and executed by a BPEL engine

ECE 1770 –Web Service Composition BPEL - Overview Use Web Services Standard as a base 1. Every BPEL is exposed as a web service using WSDL. And the WSDL describes the public entry and exit points of the process 2. Interacts through WSDL interfaces with external web services 3. WSDL data types are used to describe information flow within the BPEL process

ECE 1770 –Web Service Composition BPEL - Process Overview

ECE 1770 –Web Service Composition BPEL - Process Models Provides support for two business process models Executable Models the behavior of participants in a specific business interaction, a private workflow Abstract Business protocols in BPEL, specify the public message exchanges between parties

ECE 1770 –Web Service Composition BPEL - Activities Basic Activities: Interacts with external services,, and Structured Activities: Internal process control flow sequential flow, conditional branching, looping, and etc.

ECE 1770 –Web Service Composition BPEL - Containers and Partners Containers Data exchanges in the message flow e.g. WSDL messageType Partners Any services that the process invokes OR any services that the invokes the process

ECE 1770 –Web Service Composition BPEL - Code A sequence

ECE 1770 –Web Service Composition BPEL - Others Transactions and Exceptions Building on top of WS-Coordination and WS-Transaction specifications Transaction A set of activities can be grouped in a single transaction through the tag Can specify compensation handlers (rollback) if there is an error Exception Handling Through the use of throw and catch (similar to Java)

ECE 1770 –Web Service Composition BPEL – Example Process

ECE 1770 –Web Service Composition WSCI XML-based language Defines the choreography describing the messages between web services that participate in a collaborative exchange Only describes the observable behavior between web services No single controlling process managing the interaction

ECE 1770 –Web Service Composition WSCI - Actions Actions represents a unit of work and would typically map to a specific WSDL operation WSDL describes the entry points of each service WSCI describes the interactions among these operations External services are invoked through tag Supports transaction and exception handling

ECE 1770 –Web Service Composition WSCI - Snippet Note: this WSCI is from the perspective of the Agent, there would also be WSCI file for other parties in the process

ECE 1770 –Web Service Composition BPML XML-based language Incorporates WSCI into the standard WSCI used to describe public interactions BPML used to develop private logic implementations Provides similar process flow constructs and activities as BPEL Transactional support and exception handling

ECE 1770 –Web Service Composition Summary BPEL and BPML focuses on creation of business processes Describe an executable process from the partners perspective WSCI focuses on public message exchanges between web services Each participant in message exchange defines a WSCI interface

ECE 1770 –Web Service Composition Summary

ECE 1770 –Web Service Composition Some Open/Closed Source Engines BPEL IBM WebSphere Process Server + WebSphere Integration Developer $5014 for a 12-month license Microsoft BizTalk Server Standard Ed. for $8499 USD and Enterprise Ed. for $29999 USD Open Source Twister $0 Eclipse - SOA Tools Platform $0

ECE 1770 –Web Service Composition Discussion Security in Web Service Composition and Web Service in general A number of standards like XML Digital Signatures and Encryption, WS-Security Provide authentication and authorization of users, and for securing the XML message itself But composition standards do not offer direct support for security! In BPEL, how do the roles defined for each partner relate the existing authentication standards?