Web Services Acronyms, Demystified
by Pavel Kulchenko | Pages: 1, 2

IBM

HTTPR brings reliability for HTTP transport, so any SOAP interaction built on top of it will benefit from transport reliability in a way that doesn't require any changes to the framework. The same result can be achieved using MQSeries or other reliable transports.

The combination of the WSDL, WSEL and WSFL specifications implements three levels of functionality, required to support business processes and workflow: description of services (WSDL), non-operational characteristics (WSEL), and interaction and composition of services (WSFL).

WSCM and its sub-proposal WSXL address how Web services are componentized. "IBM is pleased to contribute WSXL to be considered as part of WSCM," says Bob Sutor, director of e-business standards strategy at IBM. "As an XML and Web services-centric component model for interactive Web applications, WSCM will enable businesses to more easily distribute those interactive Web applications through multiple channels. It will also help create new ones by leveraging existing resources across the Web. IBM is a longtime supporter of OASIS, and we're very happy to have the opportunity to chair the OASIS WSCM Technical Committee."

UDDI and WS-Inspection complete the stack, allowing the query of public or private repository for available services based on business or technical criteria (UDDI) or the query of a Web service provider for range and characteristics of available services (WS-Inspection). WS-Inspection, introduced by IBM and Microsoft, superseded two other standards from those companies: DISCO (Microsoft) and ADS (IBM).

Now, on to Microsoft's view of the Web services world:

Microsoft

Microsoft published several specifications that define packaging and extensions. For example, the DIME specification defines a binary packaging format, as an alternative for MIME-based SOAP with Attachments (SWA). A group of SOAP extensions (WS-Security, WS-License and WS-Routing) are integrated as part of Microsoft's Global XML Web Services Architecture. Keith Ballinger, program manager in Microsoft, pointed out to me that those are not really acronyms, however for the sake of completeness we will also cover them here. WS-Security (similar to SOAP-DSIG) defines how to use XML Signature and XML Encryption specifications in SOAP messages. WS-License works in combination with WS-Security and defines how digital credentials and their semantics can be associated with SOAP messages. WS-Routing (formerly SOAP-RP) describes how to enable SOAP messages to travel across multiple destinations along a message path. WS-Referral is a protocol that enables the routing between SOAP nodes to be dynamically configured.

The description layer consists largely of three specifications: WSDL, WSML and XLANG. WSDL defines service description, XLANG defines message exchange behavior from the business perspective and WSML defines the mapping between Web service functionality and the methods of a COM object behind it.

Other companies and groups are also backing their own specifications in addition to the widely supported ones like SOAP, SWA, WSDL, and UDDI. United Nations Centre for Trade Facilitation and Electronic Business (UN/CEFACT) and OASIS sponsor ebXML, a modular suite of specifications that uses SOAP and SWA for their Messaging Service, but has their own specifications for description and discovery layers: Collaboration Protocol Profile (CPP) for description and ebXML Registry Service for discovery. HP has WSCL as part of their Services Framework Specification that addresses problems in the same domain as XLANG and WSFL.

Several pieces like transaction support and management interfaces are still missing, so we may expect new specifications coming into existence during the next year. Expect to see even more acronyms. All these moving pieces sometimes make me nostalgic for XML-RPC.

Resources

• OASIS, IBM: Web Services Component Model (WSCM)
• Sun: Open Net Environment (SUN ONE)
• HP: Services Framework Specification
• Microsoft: Global XML Web Services Architecture
• UN/CEFACT, OASIS: ebXML

O'Reilly & Associates recently released (December 2001) Programming Web Services with SOAP.

• Sample Chapter 3, Writing SOAP Web Services, is available free online.

• You can also look at the Table of Contents, the Index, and the Full Description of the book.

• For more information, or to order the book, click here.