The objective of Coral is to facilitate the creation of DRM interoperability services, by third parties who have incentive to do so, which work among existing DRM technologies.  For example, broadband service providers could build interoperability services based on the Coral and Ecosystem-A specs and sell them to consumers who want their digital content to work on all of the devices in their homes. 

This contrasts with other DRM interoperability efforts, such as the Digital Media Project, which ultimately require migration to new DRMs instead of integration with existing ones.  Coral has fallen short of the admittedly lofty goal of providing interoperability among existing DRM technologies without any cooperation from vendors of those technologies, but it has kept the requirement for such cooperation to a minimum.  More on this later.

Coral's core architecture includes roles, which are functions, and nodes, which are physical realizations of collections of roles.  Perhaps the most interesting roles in the Coral architecture are the Content Mediator and Rights Mediator roles, which determine whether one system should be allowed to exercise rights on a particular piece of content from another system.  Other roles include DRM Content Exporter, DRM Content Importer, and DRM License Mapper.  The latter maps rights in one system to rights in another by making reference to a set of policies. 

Nodes are combined into Ecosystems, which are collections of nodes that are considered mutually trustworthy so that they can interface with one another without security concerns that lead to diminution of functionality.  The entire architecture is based on NEMO (Network Environment for Media Orchestration), a secure messaging scheme based on X.509 identity certificate and SAML security assertion standards.  NEMO is part of both Coral and the Marlin DRM spec; it was invented by Intertrust, the company at the heart of both specs.

Coral is quite flexible; as the architecture overview document shows, it allows for roles and nodes to be grouped together according to network and service provider architectures.  One example shows rights mediation and mapping services all taking place over the Internet, as would be the case if a broadband service provider were offering them.  Another example shows not only rights mapping but also content transcoding and transformation of DRM packaging (encryption) schemes, all taking place with a local network -- though perhaps periodically checking with a network service to ensure that policies are still valid, device keys have not been retired, and so on.  This type of arrangement could be embodied in a "control center" device for a home network, such as a PC or set-top box. 

Coral's generality and extensibility, together with the consortium's desire to be as neutral as possible with respect to specific vendors and technologies, result in an architecture document that is often abstract, hard to follow, and weak on real-world examples.  That's a shame, because Coral is by far the most pragmatic among the current bevy of putative DRM interoperability standards.  (The only DRM interoperability schemes that are more pragmatic than Coral are de facto special-purpose schemes like RealNetworks's Harmony and various unauthorized hacks.)

The Ecosystem-A spec and accompanying whitepaper were apparently designed to address some of these issues.  Ecosystem-A instantiates and extends the Coral core architecture for the specific application of content interoperability in home networks.  It implements, among other things, two concepts that are becoming increasingly familiar in this context: rights lockers and domain management.  Rights lockers are repositories of licenses to content that principals (users and/or devices) hold, and domains are groups of devices that act as single principals for licensing purposes.  (Ecosystem-A also enables the definition of tiers, which are subsets of devices in a domain, such as all those that share common characteristics, e.g., high-resolution video displays.)

Now that Coral has released a complete technical spec, apparently with the backing of a broad -- if incomplete -- set of stakeholders, the consortium's task necessarily moves from the technical to the political.  Would-be DRM interoperability providers cannot simply achieve interoperability among arbitrary technologies independently; they must have some level of cooperation from vendors of the technologies that will interoperate and from content rights holders. 

To be very specific, it is not possible to use Coral to interoperate between Microsoft Windows Media or Apple FairPlay DRMs and other technologies unless and until those vendors modify their technologies to make them Coral-compliant.  Neither Microsoft nor Apple is a member of Coral.  This is not unexpected; market leaders have little incentive to cooperate with "open standards" initiatives that direct affect their market positions, so they generally do not participate in them.

The reality is that Coral primarily represents the interests of "media player" consumer electronics (CE) vendors, such as Panasonic (Matsushita), Sony, Samsung, LG, and Philips, some of whom have their own DRM-related intellectual property and all of whom must operate within a universe that Apple and Microsoft currently dominate.   

That's why it is particularly appropriate that Coral concentrate on the emerging "home entertainment networking" paradigm in the near future, as it is doing now with Ecosystem-A, instead of a more established market such as online and portable music. 

Home entertainment networking is an extremely early market that CE vendors find highly attractive for its potential to lead to new products that can sell at high margins.  It is one in which there are a few incumbents -- mainly Microsoft and legacy conditional access (CA) technology vendors like NDS, Thomson, and Irdeto Access -- but no clear leaders.  It is also a paradigm with which media companies are getting increasingly comfortable from a content licensing perspective.

This all means that Apple and Microsoft may have more incentive to join Coral as this market develops, particularly if the Coral consortium can get service providers to create interoperability services that consumers will actually buy.  It's a bit of a chicken-and-egg situation.  But Coral is helped by the cooperation of all of the above-mentioned CA vendors as well as a real critical mass of content providers that includes IFPI, RIAA, MPAA, all four major music companies, and four major movie studios. 

In addition, a handful of major network service providers are involved in Coral, including AOL, Comcast, and Time Warner Cable.  Coral's most obvious next step is to get those companies -- and potentially others, particularly outside of the US -- to build pilot Coral-based services in cooperation with its core CE vendor community. 

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