DSML helps directories work together

Soon people and machines on the Internet will move beyond downloading Web pages, launching full-blown Web applications or working in monolithic enterprise applications. Instead, they'll use so-called Web services, which are platform-neutral application nuggets automatically assembled for each user or machine.

Companies are embracing this change by breaking up enterprise applications into small components of functionality, wrapping them in XML and preparing to share them with customers and partners. As this transformation plays out, network managers will still need to help users find the Web services that will carry out business processes.

Directories will provide that help. Directories are being enabled to operate across corporate boundaries, pointing users to services wherever they exist. To accomplish this work, directories need to be able to speak a common language. Enter Directory Services Markup Language (DSML), the emerging standard that expresses directory content in the Internet's lingua franca for commerce - XML.

Directories typically store and manage information about each user in an enterprise - including names, addresses, phone numbers and access rights. Directories are increasingly storing metadata about available Web services, what they do, what they require for inputs, how to execute them, what the results will be, who wrote them and how to pay for them. Combined with the power of XML, this information enables whole new classes of individually tailored applications for e-commerce.

DSML 1.0 - now being reviewed by the Organization for the Advancement of Structured Information Standards, the World Wide Web Consortium and the BizTalk initiative - is being pushed by Bowstreet Software, IBM, Microsoft, Novell, Oracle and the Sun-Netscape Alliance. DSML defines the XML schema for describing directory structure and data.

Applications consume DSML documents as they would XML because DSML is a subset of XML. Applications can transmit DSML documents to other DSML-enabled applications on the Internet. This process effectively extends the Lightweight Directory Access Protocol (LDAP) across firewalls to any Internet transport protocol - such as HTTP, FTP or Simple Mail Transfer Protocol - a major benefit for business-to-business efforts.

Standard tags defined by DSML include objectclass, entry, attr (for attribute) and name to refer to well-established directory analogs. To understand how these tags work, consider two directories: one for Vendor A and one for Vendor B. Directory Vendor A uses "FullName" to describe the attribute in a directory that is the name of a company's employee. Directory Vendor B uses "Name" alone for the same purpose. Traditionally, this difference would force developers to write new code to make the directories work together. DSML reconciles the differences by providing a third language both directories speak, XML.

A real-life DSML transaction might begin with an XML-enabled application making an HTTP request to a Web service that queries a directory through LDAP or directory APIs. The resulting DSML document (containing directory data) is returned to the XML application over the Web. The application then parses the XML using standard Extensible Stylesheet Language to integrate the directory data into a purchase order form, for example, within the application. With DSML, an XML application could request data and schema information from directories and consolidate this into one document.

To DSML-enable their directories, network managers will use extensions to their current directories that simply return query results in DSML. Querying isn't currently defined in DSML 1.0, but the DSML working group (DSML.org) is already working on a query markup for DSML 2.0. Either way, LDAP and vendor APIs will remain in place, and directories will continue to operate in their traditional manner, except with new business-to-business Internet commerce capabilities.

Hay is Web automation system product manager at Bowstreet Software and a lead author of the DSML 1.0 specification. He can be reached at thay@bowstreet.com.

DSML overview
More on the markup language.