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What is XDI?

XDI (XRI Data Interchange) is an emerging structured data sharing protocol from OASIS based on the XRI structured identifier standard (see the one-pager on XRI). It has been under development since 2004 by many of the same individuals and companies working on XRI.

How is XDI different from conventional XML?

XDI is a new approach to data sharing that does for machine-readable data what HTML or PDF does for human-readable content: puts it into a standard format any XDI-enabled system or application can read. This is a very different approach than conventional XML, where each XML document uses its own schema (way of identifying and describing the data it carries). By contrast the extremely simple XDI schema is standard across all XDI documents. The key is that every item of data, from the smallest atomic field to the largest multi-terabyte database, is identified, described, and linked using XRIs.

How is XDI different from RDF?

As explained in The XDI RDF Model, XDI is RDF. Technically it is an RDF vocabulary. RDF (Resource Description Framework) is the basis for the W3C’s Semantic Web initiative - a set of standards for expressing metadata (data about other data) that enable machines to more intelligently and efficiently find and process information on the Web. XDI is a highly optimized form of RDF designed for cross-domain data sharing. XDI documents typically use a compact serialization format called X3 (very similar to JSON) that is much simpler and more streamlined than RDF XML. However all XDI documents can be instantly transformed into RDF XML documents if needed. See the XDI Converter for examples.

What are XDI link contracts?

Because of the 100% addressable shared graph model, XDI documents can be used to control the sharing of other XDI documents. These are called link contracts because they serve the same purpose as real-world contracts (e.g., a non-disclosure agreements) that define who has access to what data for what purpose. Link contracts are an Internet-scale solution for authorization, access control, and data rights management.

What problems will XDI solve for users?

Data portability and protection. A primary application of XDI is to make personal profile information – anything from contact data and travel preferences to financial data and medical records — portable across websites and applications everywhere. Think "PDF for personal profile data". The combination of XDI data portability and XDI link contracts can give users significantly greater control over sharing and usage of their personal data.

What problems will XDI solve for businesses?

Automated data sharing and user-centric data management. XML has already been a boon for data interoperability and service-oriented architectures. XDI is the next evolutionary step. By adopting a common data sharing format and Internet-scale data addressing model, XDI can automate many common data sharing and integration operations that currently require much more expensive solutions. XDI also enables bridging the worlds of personal, social, and enterprise data sharing while helping ensure that the proper data is always shared and managed in the proper context.

What software supports XDI today?

The OASIS XDI standards build on the OASIS XRI standards, the second generation of which was just completed in spring 2008. The first formal XDI specifications are expected in early 2009. However there is already an open source implementation of the proposed specifications called XDI4J (XDI for Java). Visit its demonstration site for complete set of simple XDI applications and utilities.

Where can I go for more info?

Start at the Wikipedia page on XDI– the XDI community uses this to maintain current links to all relevant resources. And read the The XDI RDF Model document from the OASIS XDI TC.