'identifier' element and its attribute 'type'

[kitchenprinzessin3880]

1. The attribute 'type' has default value of IGSN. Why do you specify an enumerated list (/include/identifierType.xsd) as possible values of the attribute? Check datacite schema for correction.
2. May consider using xsd pattern regexp to validate the value of the identifier element; this may also avoid cases where users specify IGSN in various ways, with igsn prefix (IGSN:HRV003M16), with handle (10273/XX), with full URL (http://handle/....IGSN:HRV003M16)
3. Add identifier definition : "An identifier is a sequence of characters that uniquely identify a resource."

[smrgeoinfo]

suggest edit to #3:
"An identifier is a sequence of characters that uniquely identifies a resource in some scope."

the identifier scheme defines the scope.