Client-server

A client-server network application is one in which a client, thin client or [fat client]?, which instantiates the [user interface]? of the application, connects with an [application server]? or database system. When a client connects directly to a database system, or to a monolithic [application server,]? the architecture of the application is a 2-tier architecture. In recent years, it is more common for a thin client which does not incorporate [business logic]?, but only [user interface]? elements to connect to an [application server]? that implements the [business logic]?, and which transitively (i.e. in turn) communicates with a database server, which stores the raw data used by the application. Such an architecture is called a 3-tier architecture, which is a special case of n-tier architecture.

In general, n-tier architectures may employ a number of distinct services, including transitive relations between [application server]?s implementing different functions of [business logic]?, each of which may or may not employ a distinct or shared database system.