Their advantage and potential for improvement of library service at various levels are discussed. Both must agree beforehand on the meanings assigned to such patterns.
Character sets are agreements on meanings assigned to patterns that computers can process.
Escape codes announce that the meanings for certain patterns have changed. This allows roman, Cyrillic, and other alphabets to reuse the same patterns. Providing unique identification for the thousands of ideographic characters used by East Asian writing systems requires longer patterns. The large number and infrequent occurrence of East Asian characters make a technique for easy addition of needed characters desirable.