This part of ISO/IEC 11179 restates and elaborates on the procedures and techniques of ISO/IEC 11179-3:2003 for registering classification schemes and classifying administered items in an MDR. All types of administered items can be classified@ including object classes@ properties@ representations@ value domains@ and data element concepts@ as well as data elements themselves. This part of ISO/IEC 11179 develops a set of principles@ methods@ and procedures for specifying what is needed (at a minimum) to document the association between the various types of administered items and one or more classification schemes. This includes the names@ definitions@ and other aspects of the classification scheme and its contents. These can be captured through use of a set of attributes. Particular attributes are specified in this part of ISO/IEC 11179@ along with a structure for the contents of these attributes. Users may extend the set of attributes as necessary. Additional information may accompany a taxonomy or ontology; for example@ to provide a suggested set of qualifiers that could be applied to the object class@ property@ or representation taxa to more fully qualify the classification of the particular administered item. This part of ISO/IEC 11179 summarizes the basic attributes and model specified in ISO/IEC 11179-3:2003. An example in this part of ISO/IEC 11179 shows how selected components of data elements can be associated with a classification scheme through the attributes specified in this part of ISO/IEC 11179. Use of one or more classification schemes is intended to provide a sound conceptual basis for the development of metadata having enhanced semantic purity and design integrity. This part of ISO/IEC 11179 does not establish a particular classification scheme as preeminent. Sanction of a particular taxonomic approach and/or a particular epistemology is also beyond the scope of this part of ISO/IEC 11179. These are addressed by other standards committees and/or tend to be tailored to a particular domain of discourse. The power of the classification scheme and the utility of the content are appropriate areas for competition. Other standards committees are developing or have developed normative languages for use in classification and/or particular techniques and structures that can be accommodated by this International Standard. For example@ the National Information Standards Organization (NISO) has developed a standard for development of a thesaurus. It is appropriate for each classification structure to be documented as to how it was developed and how it can be extended and maintained. Such attributes could be added@ by the principle of extensibility@ to the attributes specified in this part of ISO/IEC 11179. They are not@ however@ included here. Each Registration Authority@ as described and specified in ISO/IEC 11179-6@ may classify administered items according to the classification schemes@ structures@ and content that it deems appropriate. In documenting the classification aspects of administered items@ the Registration Authority may use the principles@ methods@ procedures@ and attributes specified in this part of ISO/IEC 11179.