Pkeys and fkeys
- Every row of a table contains a unique primary key, or ‘pkey’ as its first field. This key identifies the record or table type (2 or 4 upper-case letters), a version number (2 or 3 digits) and a row number (4 or 5 digits)
- Table types optionally include foreign-key (fkey) fields. The value of an fkey must match the pkey value of its associated container or superclass ‘parent’.
- Non-key attributes, fkeys to ‘is_a’ superclasses, and fkeys to ‘is-part-of’ containers are distinguished by different values for the is_key meta-attribute in meta-table TA:
fKey type: Not a Key isPartOf is_a