Implementation Technologies

There are four technologies at your disposal; two of them are component based, described in the first two subsections that follow, whereas the other two are messaging based, described in the two subsections that follow.

COM+ Component

COM components are software components that conform to Microsoft's binary object model protocol standard. These components may be implemented using any of the supported languages on the Windows platform. COM+ is a powerful runtime environment for COM components that provides declarative transaction support, scalability, security, and other enterprise-level features.

The role of a COM+ component in a BizTalk XLANG schedule is to provide an opaque and efficient implementation of an irreducible yet reusable business function. A developer writing such components has access to the entire Win32 API and advanced language features for expressing and debugging business-relevant algorithms. An additional benefit is that these components are compiled, and hence their deployment and maintenance is more manageable.

The BizTalk Server product includes as part of the standard installation COM components that any program, including an XLANG schedule, can use. For example, the IInterchange method or the Microsoft BizTalk Server Interchange 1.0 Type Library can be used to submit documents to BizTalk Messaging Services.

Script Component

Windows scripting technology is a lightweight approach to writing COM components. These components have some of the same features of COM components described previously and can be installed in COM+ applications; however, there are some differences:

• Script components are vulnerable to tinkering, and this may be desirable if some aspects of an implementation are yet unclear and there is a need for this type of flexibility.

• Script components are more difficult to debug.

• The method calls are late bound, and there is no type enforcement, except possibly at runtime.

• A script component cannot contain an implementation for multiple classes nor can a class support multiple interfaces.

• All argument references used in a function call must be made by reference and not by value.

• Only function calls may be used; subroutines are not supported.

MSMQ Message Queuing

MSMQ message queuing provides a robust, scalable, and secure platform for sending messages between an XLANG schedule and another application. Unlike the COM+ and scripting components described previously, messaging facilitates loosely coupled asynchronous communication between applications, a desirable attribute when building scalable applications.

Message queues are persistent, fault tolerant, scalable, transactional, and secure. MSMQ message services are an important part of an overall application design. The XLANG schedule can directly address such MSMQ queues to integrate business processes with physically or temporally distant applications or components.

BizTalk Messaging

The BizTalk Messaging implementation shape provides access to a BizTalk Messaging channel. This Messaging shape allows an XLANG schedule instance to gain access to the reliable document delivery and transformation services provided by BizTalk Messaging. With this implementation technology, an XLANG schedule can post a document directly into a BizTalk channel, or vice versa, a BizTalk Messaging port can post a document directly into an XLANG schedule, starting a new instance of the schedule if necessary.