Microsoft BizTalk Server  Orchestration Services

Microsoft BizTalk Server, a member of the Microsoft .NET Enterprise Server family of products, provides a robust set of services that enables both developers and business analysts to simplify some of the more complicated tasks associated with integrating business processes that span applications, platforms and businesses over the Net. In a traditional programming environment the integration of two or more applications would require a number of very daunting and sometimes time consuming tasks that can be exponentially complicated by the environments in which the applications are deployed. Application data is typically stored in a variety of formats and data schemas on multiple platforms physically distributed both internally and externally to the host corporate network. The integration solution usually requires several business analysts and teams of developers to design, develop, code and test the developed application integration process. Typical development tasks include data transformation utilities, routing and delivery utilities to facilitate the delivery of data between the applications as well as one or more additional background applications to manage the overall process. BizTalk Server simplifies these tasks and by giving developers the tools and underlying plumbing they need to tackle the challenge they face in the enterprise application integration (EAI) space as well as the similar but unique challenges faced in the business-to-business (B2B) integration application space.

The BizTalk Server product provides two distinct feature areas that help developers integrate applications, BizTalk Messaging and BizTalk Orchestration. BizTalk Messaging provides reliable document delivery and routing services as well as data transformation and mapping services. These services, as well as a wide range of additional services to ensure the data's integrity, delivery and security, provide a standard gateway for the sending, receiving and transformation of documents across the Internet, Intranet and Extranet. BizTalk Orchestration services provide a development and execution environment that integrates loosely coupled, long-running business processes, both within and between businesses. It allows business analysts and developers to visually model their business processes using a Visio-like design environment and then bind that visual representation to its physical implementation. There are many situations that require the employment of both functional areas of the product, for example: A long running business process that requires data transformation and routing services however in this article we are going to focus on the Orchestration services provided by Microsoft BizTalk Server product.

The BizTalk Orchestration Designer

When you define a business process what you're really doing is defining the message exchange protocol between the participants in that process. In order to define a business process, you need to determine the logical order of actions and the corresponding flow of messages. The sequences of steps in a business process are frequently asynchronous and can be performed by one or more independent and sometimes distributed participants, typically applications, who may or may not be performing related tasks. To help document these types of complex relationships and dependencies we traditionally use business process modeling tools and standards, such as workflow diagrams and interaction diagrams. BizTalk Orchestration extends the concept of the interaction diagram and the workflow diagram by providing the definition and execution environment for concurrent actions and decisions and transactions that cannot be expressed in a static interaction or workflow diagram.

To accomplish this BizTalk Server Orchestration provides a Microsoft Visio 2000based design tool called the Orchestration Designer that gives you the ability to create business process drawings that can be compiled and run. You use the Orchestration Designer to create drawings that describe loosely coupled business processes. These business processes can be long-running asynchronous processes that span unlimited timeframes or synchronous processes that span just minutes or seconds. When you create an orchestration drawing you design the business process in the left hand design panel using the flow chart stencil and then bind that business process to it's implementation in the right hand panel using the implementation stencil. (Figure A).

Figure A  The Orchestration Designer

The Orchestration Designer provides three major types of shapes to help you implement a business process; Flowchart, Implementation and Communication shapes. Flowchart shapes are connected to represent the process flow in a business process. Once you've designed your process flow using the Flowchart shapes you connect the shapes to implementation shapes. The process of connecting a Flowchart shape to an implementation shape creates a communication shape named Port. A Port represents the flow of and the communication of messages in the business process. A Message is defined as a packet of data that is sent or received by an Orchestration schedule and can consist of an XML document or text stream.

The designer also gives you four design pages to help you define your business process and message flow. If you look at the bottom of Figure A you should notice several tabs visible on the drawing surface, these are known as design pages. A description of these pages is given below.

7        Business Process page.  On this page you use Flowchart shapes and Implementation shapes to define a business process.

• Data page. On this page you use Communication shapes to control the flow of data between message fields. BizTalk Orchestration Designer provides these shapes automatically.
• On Failure of Transaction page. On this page you can use Flowchart shapes and Implementation shapes to design an alternate business process for a failed transaction.

7         Compensation for Transaction page. On this page you can use Flowchart shapes and Implementation shapes to design an undo process for a committed transaction.

When you first begin to design your business process you start on the Business Process Page by dragging, dropping and connecting Flowchart shapes. There are nine flowchart shapes; Begin, End, Action, Decision, Abort, Fork, Join, Transaction, While. Every schedule must start with the Begin shape and conclude with the End shape. The Action shape defines the sending and receiving of messages in the business process. Forks, Joins, Decisions and While shapes can be connected to Actions to help define the semantics of the business process being modeled. The Transaction shape represents a collection of actions that are either all executed or not all executed and supports three types of transactions: short-lived, long running and timed. Short-lived transactions are ACID, DTC transactions. Timed transactions fail after a time period designated in the properties of the transaction in the schedule. Long running transactions are a collection of actions that send and receive messages over a long period of time and usually contain nested short-lived transactions. When a transaction is aborted the Orchestration engine will execute the process defined on the Compensation for Transaction page or the On Failure of Transaction page of the Orchestration schedule. The nine Flowchart shapes available in the Flowchart stencil are listed below.