Requesting which of these will deter attorneys from communicating with an investigator solely for the purpose of disqualifying that investigator?

Rhapsody's service, provided by RealNetworks, is an example of a(n):

A) instant messenger service B) online music service C) junk e-mail filtering service D) e-mail service provider

Provide the equivalent domain relational calculus and relational algebra expressions for each of the tuple relational calculus expressions given in Exercise 4.10.

(a) {H.hotelName | Hotel(H) ? H.city = ‘London’} (b) {H.hotelName | Hotel(H) ? (?R) (Room(R) ? H.hotelNo ? R.hotelNo?? R.price ? 50)} (c) {H.hotelName | Hotel(H) ? (?B) (?G) (Booking(B) ? Guest(G) ? H.hotelNo ? B.hotelNo?? B.guestNo = G.guestNo ?? G.guestName = ‘John Smith’)} (d) {H.hotelName, G.guestName, B1.dateFrom, B2.dateFrom | Hotel(H) ? Guest(G) ? Booking(B1) ? Booking(B2) ? H.hotelNo ? B1.hotelNo?? G.guestNo = B1.guestNo ?? B2.hotelNo = B1.hotelNo ? B2.guestNo = B1.guestNo ?? B2.dateFrom ? B1.dateFrom}