... assignments in Billing, 18 5 interface, 11 1 12 unified messaging, 202 Business models, 18 2–85 closed, 18 2, 18 4 open, 18 3, 18 4 table, 18 4 Byte-encoded WML, 30 Cell broadcast, 17 1 Channel definition ... 14 7 public-key, 14 8– 51 role, 14 6 schemes, 15 1–52 summary, 15 4 symmetric-key, 14 8 types, 14 8 See also Security Customer expectations, 17 0 psychological user barriers, 17 1 relation management ... positioning, in WAP gateway protocol stack, 10 1 provision of, 10 2 push, 11 1 scaleable n-tier, 220–23 serviceperson, 8 telephony, 8–9 using, 7–9 vertical, 18 0 WAP, 7–9, 223–26 wireless environment...