Eran just announced the second draft of OAuth Discovery, the first implementation of the XRDS-Simple specification that I mentioned here just over a week ago.

What’s significant about this announcement, as Eran points out, is that the new draft is already implemented and deployed by FireEagle (a Yahoo! Brickhouse service), Ma.gnolia, and Get Satisfaction — three leaders in the OAuth community. On the development tools front, Mediamatic will release initial support for discovery early next week with full support due early May in their OAuth PHP library.

This draft is a complete rewrite of the first draft released several months ago and, in the spirit of OAuth, greatly simplifies the concepts and presentation of the protocol, and incorporates a great many of the clarifications provided by the OAuth and XRI communities.

OAuth Discovery, simply, is an extensible, machine-readable format for identifying OAuth-protected resources and service endpoints. Take a look at the provided example or Ma.gnolia’s actual discovery profile to get an idea for what these documents look like.

Over time, the goal is to automate the pairing of unacquainted web services, by being able to first identify the location of services on the web and second to discover the authentication requirements for accessing such services. Coupled with XRDS-Simple, you can further specify the types of data available from given services, and to begin to describe the methods you would use to access that data.

To provide a more complete conceptual model, imagine that you run a social network, and in this network, members have collections of bookmarks. Your service provides a way to either upload bookmarks directly or to subscribe to someone’s existing bookmarks stored at, say, services like Delicious or Ma.gnolia. Now say that you also encourage new members to sign in with an OpenID identity. From that identity, you may be able to discover an XRDS-Simple profile that points to an existing social bookmarking account, allowing you to attempt to import those bookmarks immediately. If, however, those bookmarks require authorization, and the authorization protocol happens to be OAuth, you should be able to automate the appropriate authorization requests to the user because the service supports OAuth Discovery.

In contrast, to achieve the same flow today, you must manually provide the names of accounts and services that you use individually, and then hope that the new service supports the remote protocols of your pre-existing services. With XRDS-Simple and OAuth Discovery, much of this work is automatically handled for you, letting you focus more on what you want to share, and less on where your data is stored, and increasingly allowing data to automatically flow between systems, should you decide to provide them authorization to do so on your behalf.

If you’re interest in learning more about OAuth Discovery, the best place to go is the OAuth Extensions group. Since OAuth Discovery also borrows heavily on XRDS-Simple, you might also want to check out that specification and discuss it in the related group.

Developed through the standardization of the best practices of several well established proprietary industry protocols, OAuth is similar to Google AuthSub, FlickrAuth, AOL OpenAuth, Yahoo BBAuth, Upcoming API authentication, and Amazon Web Services API authentication.

However, OAuth is non-proprietary, and does not require a specific user interface or interaction pattern. Service Providers do not have to specify how they authenticate Users, making the protocol ideally suited for cases where authentication credentials are unavailable to the websites, such as with OpenID. OAuth is designed to complement, rather than replace, authentication protocols such as OpenID.

Application developers can easily and safely create “mashups” across multiple web services, and web site developers can enable rich user experiences without their users sharing passwords with untrusted sites. OAuth was carefully designed for the needs of service providers ranging from the smallest PHP application to the largest industry scaled web services platforms, and for the needs of consumers such as multisite mashups, desktop tools, cellphones, set-top boxes, and internet connected appliances.

Open source code libraries are available for PHP, Ruby, Python, Java, C#, and Perl. More information and complete documentation can be found at the project homepage http://oauth.net.