Rounding up Web services intermediaries

WSIs (Web services intermediaries) are a unique class of middleware for managing and monitoring Web services. Useful for everything but the smallest of Web services applications, WSIs provide important features such as message routing, security, exception handling, abstraction, message transformation, and logging.

As vendors fine-tune their products, add features, and improve usability, WSI options are getting better. Over the last few months, several new versions of WSI products have popped up: Actional Looking Glass 5.0, AmberPoint SLM (Service Level Manager) 2004, Grand Central BSN (Business Services Network) 4.0, and Infravio Ensemble 4.1 (the component I tested is now known as X-Broker).

Each of these products differs significantly in their approach to intermediating Web services, but a cursory review of their feature sets doesn't readily reveal that difference. The significant contrast is in the metaphors they use for management and the presentation of information; each WSI emphasizes different aspects of the intermediary game. Grand Central 4.0 is a hosted service, whereas Actional's approach zeroes in on service monitoring; Infravio uses contracts to define relationships; and AmberPoint SLM manages performance with service-level objectives.

Deciding which of these four tools is right for your organization will require careful consideration of your needs and the relative strengths of each product. Evaluate the WSI's management metaphor and compare it with your organization's engineering and operations philosophy. Also, be sure to evaluate the reporting and user interface based on your organization's needs.

If you get those things right, any one of these products will provide you with a proven, stable management platform for building reliable Web services applications. They are polished, ready to work, and do what they advertise.

Grand Central BSN 4.0

As a hosted service, Grand Central is unique among the four products tested. There's no software to buy or install: You simply go to their Web site and sign up. The hosted service has clear advantages in ease of setup and maintenance. Although some organizations don't like the idea of their core messages going outside their internal network, this attitude is changing as more companies take advantage of "by-the-drink" services.

The core of Grand Central's BSN provides a trustworthy, auditable, and convenient way for organizations to exchange Web services messages with other external parties. By using BSN 4.0 in combination with other services available on the Internet, building and offering services without owning any servers becomes possible.

BSN 4.0 adds several important new features for creating virtual applications. Perhaps most significant is the creation and execution of Web services processes inside the network; the most sophisticated of these features is the addition of a BPEL (Business Process Execution Language) engine.

BPEL is an executable, XML-based language for describing business processes, and BSN 4.0's BPEL engine allows developers to create, combine, customize, and reuse dynamic business processes.