Chapter 7. Tier Communications

The business tier is a critical part of any enterprise application. But it doesn't exist in a vacuum: the business tier requires an interface (often several interfaces) to the outside world. Of course, since we spent most of Chapters 3, 4, and Chapter 5 discussing the presentation tier, this should not be much of a surprise. But we glossed over something in those chapters: glueing the tiers together. Before we discuss the low-level business tier, we need to talk about integration; specifically, how data is exchanged between the tiers.

This chapter focuses on managing the communications between tiers using data transfer patterns. Our goal is to provide a basic vocabulary for talking about exchanging data between different components of the business tier and between the business tier and the presentation tier. Ultimately, we want to be able to do this in a well-structured, efficient, and flexible way.