3.6 Other rewrite rules. Other noteworthy sets of rewrite rules include the Russell Soundex system, the New York State Immunological Information System (NYSIIS), and the Henry Code. We implement the first two of these coding systems as they have been accepted by many as an academic standard. The Soundex rule set is extremely simple containing about half a dozen rules. Vowel letters are used to help define which consonant letters are to be coded, then dropped. Consonant letters fall into six codes. The resulting groups have not been efficient enough for many users. Thence came NYSIIS, with a couple of newer versions, continually getting better for names that appear in the official records kept by New York State. An enhanced NYSIIS is the most popular version. At some point this system neutralizes all vowel letters to “A” and reduces many consonant letter clusters to single general consonant letters. The results are very similar to the output of Phondex at the dialect level. The Henry Code is very much like NYSIIS, but designed for French names. The Phondex system has its own array of rule sets, each designed for its own language and/or culture.