Dewey Decimal Classification: "DDC's numbers formed the basis of the more expressive but complex Universal Decimal Classification, which combines the basic Dewey numbers with selected punctuation marks (comma, colon, parentheses etc.). Despite its frequent revision, DDC is widely considered theoretically inferior to other more modern systems which make freer use of alphabetical characters to produce shorter classmarks for concepts of equal complexity, though it continues to offer a more expressive format than the simpler enumerative alphanumeric Library of Congress classification developed shortly afterward. "