A set of XRI documents are available for public review:
The XRI specification suite presented for public review contains four parts. A non-normative document Introduction to XRIs summarizes the uses and features of XRIs and is intended to serve as an entry point for the XRI 2.0 suite. It clarifies what XRIs are in terms of the supported Uniform Abstract Identification Layer. It provides examples of the types of problems XRIs are designed to solve, for example: The Broken Links Problem (Persistent Identification); The Multiple Authority Problem (Federated Identification); The N-Squared Mapping Problem (Shared Identification); The Exploding Addresses Problem (Simplified Identification); The Bootstrap Discovery Problem (Metadata Identification); The Public Identifier Problem (Privacy-Protected Identification); The Future-Proofing Problem (Extensible Identification).
The XRI Syntax document defines the normative ABNF grammar for XRIs, transformations from XRIs into IRIs and URIs, relative XRI references, and normalization/comparison. XRI syntax "extends generic IRI syntax in the following four ways: (1) Persistent and reassignable segments; unlike generic URI syntax, XRI syntax allows the internal components of an XRI reference to be explicitly designated as either persistent or reassignable; (2) Cross-references, which allow XRI references to contain other XRI references or IRIs as syntactically-delimited sub-segments; (3) Global context symbols, or shorthand symbols for establishing the abstract global context of an identifier; (4) Standardized federation, in which federated identifiers are those delegated across multiple authorities, such as DNS names; XRI syntax standardizes federation of both persistent and reassignable identifiers at any level of the path."