In the drop-ship model of Internet retailing, suppliers
hold the inventory and accordingly execute many PDS
activities on behalf of the Internet retailer. In the
transactions between customers and Internet retailers,
the explicit services performed across the different PDS
activities simplify to only two implicit services offered as
part of two activities. The first activity, sourcing, spans
materials handling and warehousing tasks in PDS, while
the second activity, delivery, spans transportation activities
(Rabinovich and Bailey, 2004).