ISO 19115 is an international standard preferred by leading data publishers and warehouses (i.e., British National Geospatial Data Framework, Australian Spatial Data Directory, UN Geographic Information Working Group, INEGI (Mexico) and Canadian Geospatial Data Infrastructure) worldwide. CUAHSI prefers ISO 19115 for several reasons. Please follow the link for a detailed explanation. International Organization for Standardization endorses use of W3C's XML Schema as the medium for publication of ISO 19115 metadata and offers the implementation in ISO 19139. Below you may find the most recent version of ISO 19139 as a zip archieve. Archieve also contains three example metadata files and necessary GML (Geography Markup Language) schemas. Note that ISO 19139 is currently a draft international standard.

ISO 19139 XML Schemas (zip file)