The CDIF family of standards is primarily designed to be used as a description of a mechanism for transferring information between modelling tools. It facilitates a successful transfer when the authors of the importing and exporting tools have nothing in common except an agreement to conform to CDIF. The language that is defined for the transfer format also has applicability as a general language for import/export from repositories. The CDIF semantic metamodel defined for CASE also has applicability as the basis of standard definitions for use in repositories. The standards which form the complete family of CDIF standards are documented in ISO/IEC 15474-1:2002, Information technology — CDIF framework — Part 1: Overview. These standards cover the overall framework, the transfer format and the CDIF semantic metamodel. The diagram in Figure 1 depicts the various standards that comprise the CDIF family of standards. The shaded box depicts this Standard and its position in the CDIF family of standards. This standard defines the Common Subject Area of the CDIF semantic metamodel. This subject area contains meta-objects that are used as the basis of the other subject area standards, and also meta-relationships and meta-attributes that are applicable to all meta-objects. This document is intended to be used by anyone wishing to understand and/or use CDIF. This document provides a definition of a single subject area of the CDIF semantic metamodel. It is suitable for: — Those evaluating CDIF, — Those who wish to understand the principles and concepts of a CDIF transfer, and — Those developing importers and exporters. This document, ISO/IEC 15474-1:2002, Information technology — CDIF framework — Part 1: Overview, and the Framework document ISO/IEC 15474-2:2002, Information technology — CDIF framework — Part 2: Modelling and extensibility, should be read first when initially exploring CDIF and before attempting to read other documents in the CDIF family of standards. While there are no specific prerequisites for reading this document, it will be helpful for the reader to have familiarity with the following: — Entity-Relationship-Attribute modelling; — Modelling (CASE) tools; — Information repositories; — Data dictionaries; — Multiple meta-layer modelling.