IBM, HP, Others Line Up behind SOAP

Microsoft Corp. is willingly letting SOAP slip out of its grasp, and other influential companies in the industry are eager to pick up the XML specification.

Late last month the Simple Access Object Protocol (SOAP), originally developed by Microsoft (, was submitted to the World Wide Web Consortium (W3C, SOAP enjoys the support of a host of industry heavyweights, including IBM Corp. (, which helped prepare the revised version of the specification that was placed before the WC3.

SOAP is a proposed standard that would allow XML data to invoke objects running on remote servers across both corporate intranets and across the Internet. In practice, SOAP operates as a remote procedure call mechanism that leverages HTTP as a base transport and encodes requests and responses as XML documents. The original version 1.0 draft of SOAP provided support only for HTTP, but the revised version 1.1 specification supports both SMTP and FTP, as well.

SOAP’s support for a range of Internet protocols means that it can easily traverse corporate firewalls, which commonly pose an obstacle to any proposed application interoperability solution. Because SOAP object invocations can appear to a Web server as HTML code, for example, they can pass through existing firewalls without modification.

Microsoft, in particular, has been an early proponent of SOAP. The software giant developed the specification in conjunction with UserLand Software Inc. ( and Developmentor Inc. (, and submitted it to the IETF.

In October 1999, however, Microsoft upped the ante when it made SOAP the lynchpin of its proposed Windows DNA 2000 strategy. At the time, the software giant suggested that developers use the next-generation XML-based protocol to facilitate communications between applications instead of its existing DCOM.

Microsoft had initially proposed DCOM as an object model standard to compete with the likes of CORBA and the Java-based Remote Method Invocation (RMI) protocol from Sun Microsystems Inc. (

A rich object protocol such as DCOM, CORBA, or RMI is not necessarily the best choice for use in an e-business setting. Aside from the quasi-religious fervor that sometimes accompanies the promotion of one protocol standard at the expense of the other, object protocols are more difficult to program than is the XML-based SOAP. They also require considerably more tinkering at the firewall level. Because it leverages HTTP as a base transport, firewall support isn’t an issue with SOAP.

SOAP’s trade-off, of course, is richness: It is comparatively less sophisticated than its competitors. Moreover, supporters of another object protocol -- the Internet Inter-ORB Protocol (IIOP) -- claim that IIOP already addresses problems of interoperability between applications.

IBM’s support is a shot in the arm for Microsoft’s efforts to have SOAP branded as an open standard. Big Blue has been a leader in the XML field of late, proposing the much-anticipated trading partner agreement mark-up language in February of this year.

Other vendors that announced support for SOAP include SAP AG (, Compaq Computer Corp. (, Hewlett-Packard Co. (, and Ariba Inc. (

According to Zona Research Inc. (, the sheer number of high-profile vendors lined up behind the SOAP standard almost serves to guarantee its success.

"The W3C standardization process may take the better part of 2000 to achieve final adoption of the spec, but the array of co-sponsors makes its ultimate acceptance a virtual lock," writes Martin Marshall, director at Zona.

Marshall suggests IBM’s decision to embrace SOAP and its participation -- by virtue of its Lotus division -- in the version 1.1 revision of the SOAP draft are important political steps. After all, notable competitors such as Sun and Oracle Corp. ( haven’t yet announced support for SOAP; given Sun’s pronounced commitment to the Java-based RMI standard and Oracle’s avowed support of CORBA, these companies aren’t expected to do so anytime soon.

"Version 1.0 was all Microsoft, and for a while it appeared to be part of a Microsoft-grabs-XML-for-itself proprietary play," Marshall notes. "Instead, this starts to play out as a cross-platform, cross-messaging protocol [that lets] servers invoke processes on one another [and allows] XML-based B2B commerce to happen with a highly heterogeneous mixture of companies."