The paper outlines the standardization function of the Czech Subject Authority File and explores the role of UDC as a switching language, i.e. as an intermediary between various indexing systems at institutional, national and international level. Subject indexing and classification systems used at the institutional and national level may differ from one another in their levels of specificity, syntactic features (e.g. word order of terms, subject headings versus descriptors), and in the usage of terminology. These differences raise compatibility problems and make any mapping efforts more difficult. The paper explains how such difficulties may be partially overcome by means of the UDC system. The author illustrates the potential application of UDC as a linking element between different subject organization tools used by memory institutions. In this context the author discusses subject indexing systems used in libraries, museums, galleries and archives.