This schema is an implementation of the VRA Core Categories, Version 4.0. It defines a wrapper element (vra), which can hold any number of record-level elements (collection, work, image). These elements can be nested to indicate collection-work-image hierarchies. This schema extends the VRA 4.0 unrestricted schema to provide restrictions to improve interoperability. Defines a date which follows the ISO 8601 date format, and allows right truncation (unlike the XML Schema date datatype). This datatype does not allow for time or time zone information. In brief, the following formats are allowed: present 2006 (2006) 2006-12 (December, 2006) 2006-12-31 (31 December 2006) -44 (44 BCE) -44-03 (March, 44 BCE) -44-03-15 (15 March, 44 BCE) -10000000 (10 Million Years Ago) -100000000000 (100 Billion Years Ago)