The W3C Internationalization Core Working Group has publishe a note on Requirements for String Identity Matching and String Indexing. "This document is being published as a Working Group note in order to capture and preserve historical information. It contains requirements elaborated in 1998 for aspects of the character model for W3C specifications. It was developed and extensively reviewed by the Internationalization Working Group, and is being published by its successor, the Internationalization Core Working Group, part of the W3C Internationalization Activity. The wording of the 1998 version remains unchanged (except for correction of a small number of typographic errors), but the links to references have been updated prior to this publication." At least a couple of sections are out of date, and I wouldn't recommend it for a modern implementation.