Taxonomy schema for XBRL. This schema extends the XSchema schema with several linking structures useful for XBRL taxonomies. This datatype serves as the datatype for those financial concepts in a taxonomy which denote units in a currency. Instance items with this type should have a unit of measure from the ISO 4217 namespace of currencies. This datatype serves as the datatype for share based financial concepts. This datatype defines the link between two business reporting concepts. We should eventually document this with XLink/Xpointer. This datatype defines the presentational labels that may appear for a financial concept. These can be overriden in an instance document. This datatype defines the reference to authoritative literature that may appear for a financial concept. These are references to published documents, not online resources.