Two tier -- The client process runs on a workstation
or personal computer that interacts with a server process
which runs on a shared device that is accessed through a network
Three tier -- The client process runs on a client
workstation that interacts with a server process which runs
on a server device. The server device is connected to a host
that provides services to the server device
N-tier -- The client process runs on any workstation;
the server process runs on one or more distributed server
devices. The middleware mediates all interactions between
the various processes. Components and integration adapters
allow access to various information sources.
Distributed implementations are based on multiple levels of
complexity, all of which are characterized by the distribution
of processing logic. The choice of hardware architecture,
development tools, and the development approach is influenced
by the distribution strategy that results from the business
requirements and system characteristics. Distributed development
strategies are defined in terms of distributing presentation,
function, and data access logic across the client and the
server. The presentation layer handles the user interface
and formatting information for display. The business object
layer executes the business logic and is based on core business
objects. The data access layer handles data-related processing.
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