ABSTRACT
In the first chapter of this book, we considered client-server architecture to represent a single model that varied by the way data flowed between each computer. If data flowed directly from the client to the server, the architecture could be represented as a two-tier architecture, with the client representing the first tier and the server representing the second tier. If data flowed from the client to the server and depending on the request, flowed to another server, we could refer to the architecture as being a three-tier architecture. As a review, in a two-tier architecture the user interface is typically located on the user’s desktop while the database is located on a server that provides services to many clients. In a three-tier (also referred to as multi-tier) architecture, a middle layer is added between the client and the database to be accessed. The middle layer can queue requests, execute applications, provide scheduling, and prioritize work in progress. Because a number of different types of software products can reside at each tier, this can result in a series of different client-server models and results in the title of this chapter.
