"validate_doc_update": function(n,o,u){}

Assign a function instead of a string to make validation handler consistent with the update handlers

consistent => "updates": { "hello": function(d,r) {} }
consistent => "validate_doc_update": function(n,o,u){}
inconsistent => "validate_doc_update": "function(n,o,u){}"

http://wiki.apache.org/couchdb/Document_Update_Handlers
http://wiki.apache.org/couchdb/Document_Update_Validation