@when(optional)Indicates the point of occurrence of this feature along a time line. Its value must
be
the ID of a <when> element elsewhere in the document.
Value conforms to data.URI.
@when(optional)Indicates the point of occurrence of this feature along a time line. Its value must
be
the ID of a <when> element elsewhere in the document.
Value conforms to data.URI.
@when(optional)Indicates the point of occurrence of this feature along a time line. Its value must
be
the ID of a <when> element elsewhere in the document.
Value conforms to data.URI.