Identifier is a unique identifier that is mainly used for internal purposes
in the Data Dictionary. It is a character string used to distinguish different
elements, tables and datasets within the same context. It's maximum length is
50 characters and it must have no blank spaces. Identifiers are also used as
tag names to distinguish elements in XML-formatted data, so their syntax must
apply to the same rules as those of XML tags.
NB! A table identifier must be unique within its parent dataset. A data
element identifier must be unique within its parent table.