Blazing the Trail
XrML's origins can be traced to 1996, when Dr. Mark Stefik of Xerox's Palo Alto Research Center had an idea. The best way to enable Internet commerce, Stefik reasoned, would be to develop a device that could store data under a strictly defined set of access procedures. Unless those procedures were followed, the device would act like the digital equivalent of a bank vault, allowing data neither to enter nor leave.
Stefik named this hypothetical device a "trusted system," and he published the idea in a seminal paper entitled "Letting Loose the Light: Igniting Commerce in Electronic Publishing." The paper proposed that trusted systems would require machine-readable languages for defining the access procedures. The first example of such a rights expression language was Stefik's Digital Property Rights Language (DPRL), which he based on Lisp.
Xerox waffled on plans to deploy DPRL commercially, but the language succeeded in capturing the imagination of the digital publishing industry—although not without some criticism. "In my view, DPRL is not quite ready for prime time as a standard," John Erickson, V.P. of technology strategy for Yankee Book Peddler, wrote in 1998. "Both DPRL and the electronic publishing community would be far better served if this language were XML-based."
A rights expression language built with XML would be extensible, Erickson reasoned, permitting it to adapt to the evolving needs of rights management, and giving it a much greater chance of interoperability with other emerging data standards for e-commerce. What's more, XML is human-readable as well as machine-readable. An XML-based rights expression language would make it easier for humans to comprehend and create elaborate rights policies.
As it turned out, Erickson's comments presaged another of the defining moments in DRM. That same year, Stefik and Xerox unveiled the specification for DPRL 2.0, the first XML-derived rights expression language. This iteration showed enough promise that it earned first its own business unit at Xerox, then its own company. Xerox and Microsoft launched ContentGuard in April 2000, with the aim of further refining and commercializing DPRL. The result was XrML.
On Guard
"The DRM infrastructure business hasn't gotten traction for a number of reasons," says Rajan Samtani, ContentGuard's director of sales and marketing. "Obviously XrML is not, in and of itself, going to be the be-all end-all. But we do believe this is one important foundational piece."
Samtani is being modest; in fact, ContentGuard is so convinced of the essential role that rights expression languages will play in the future of DRM that it abandoned its DRM software business in August 2001. It now concentrates exclusively on developing the XrML standard.
Central to ContentGuard's strategy is the idea that the market is likely to increasingly favor best-of-breed DRM solutions from multiple vendors. "This notion of end-to-end DRM solutions is not going to fly over time," says Samtani. Instead, he explains, XrML lets content publishers build heterogeneous networks of trusted systems, where all of the systems can communicate with one another.
How diverse can XrML's trusted systems be? In November 2001, ContentGuard published the specification for XrML 2.0, the first significant revision of the language since its evolution from DPRL. This new iteration broadened the number of supported business models beyond the Napster approach to include both content-driven and service-driven approaches. Instead of merely assigning rights to individual pieces of content, XrML 2.0 lets you define access procedures for libraries, collections, databases, or even Web services.
The most frequent criticism leveled at XrML is that the language is overly complex, because it comprises more than 100 distinct elements. However, its comprehensive feature set has earned it an impressive roster of endorsements from digital media and publishing heavyweights including Adobe, Audible, Barnes and Noble, Hewlett-Packard, McGraw-Hill, St. Martin's Press, Wiley, and Time Warner Trade Publishing.
Even given these companies' collective blessing, Microsoft remains ContentGuard's most important partner. The development of Microsoft Digital Asset Server indicated that XrML had moved beyond white papers and specifications to become a real-world solution with active deployment. Thus, XrML remains unique, even though it must now share the market with some more recent challengers.
