The main purpose of ClaML is to formally represent the content and hierarchical structure of healthcare classification systems in a markup language for the safe exchange and distribution of data and structure between organizations and dissimilar software products. The scope of healthcare classification systems covered by this document encompasses terminologies@ and is constrained to traditional paper-based systems (like ICD-10) and systems built according to categorial structures and a cross thesaurus (like ICNP)[2]. ClaML is intended for representation of healthcare classification systems in which classes have textual definitions@ hierarchical ordering@ named hierarchical levels (such as ??chapter??@ ??section??)@ inclusion and exclusion criteria@ and codes. It is not intended to cover any formal representation@ neither for definition or composition of concepts@ nor for specification of classification rules. Systems with such formal specifications can at best be partially represented using ClaML@ and are hence out of scope. Most of the notes and examples in this document relate to ICD. This is because ICD is the most common classification system in the scope of this document. As a highly complex classification system it is an inexhaustible source for examples of nearly any kind. But all these notes and examples represent also other similar classification systems@ if applicable@ which are usually less complex. An overview of currently known classification systems using ClaML is provided in a separate document which is electronically available (see 7.3). This document is not intended to: a) provide a normative syntax on how a healthcare classification system is to be constructed; b) define link types between elements in a healthcare classification system (this is left to the developers of healthcare classification systems); c) provide a representation for direct viewing or printing.