Multitier architecture

Server components typically implement significant business functions and mn on a server. In a multitier architecture, most business logic in an application runs on dedicated servers... 

An earlier version of the DIDB was described in Chapter 14 of the previous edition of this book (5). The new DIDB application launched in 2005 has a typical multitier architecture in a Microsoft . NET environment. The back end is a Microsoft SQL Server 2000 and the current application is deployed on a Web farm. Currently, the database has data extracted from more than 6280 published articles (1966 to 2007) related to drug metabolism and DIs and 260 product labels (1998 to 2007). The use of the Web facilitates worldwide access as well as upgrades and updates the DIDB is updated daily. 

FIGURE 3.4 Three-dimensional MRTM simulation architecture. The multitiered architecture allows middleware programs to run inside a J2EE server and also provides web services to the users of the system. 

N-Tier Architecture (multitier architecture) is a software architecture model where multiple software components serve different purposes and are physically separated, such as client-server architectures. 

Learn how a multitier architecture can help the environment and your bottom line. If you re like most organizations, you re faeed with rising costs, reduced... 

The basic constructs of type, collaboration, and refinement support all levels of specification, architecture, and implementation. However, we also pay explicit attention to specific levels of architectural design logical and physical database mapping, technical architecture (including client-server and multitier peer-to-peer architectures), and user-interface modeling. The case study touches only on some of these aspects. 

Please note that layers and tiers are two different concepts. Tiers mean the physical separation of subsystems—each subsystem runs on a different hardware or the same hardware but in different processes. In a multitiered system, the interaction between the subsystems is accomplished through remote procedure calls (RPCs). Any RPC involves network overhead and therefore has a performance penalty whether the remote procedure is on a separate hardware or on the same physical hardware but in a different process. Layers, on the other hand, are logical separations of the subsystems. Each layer can run on a different physical tier, or all layers can run on a single tier. The purpose of physical tiers is to leverage distributed hardware resources or to reuse a piece of software that is deployed on a different hardware that your system wants to leverage. The purpose of layered software architecture is to separate the system into highly cohesive and loosely coupled modules (see Chapter 2 for software development principles). 

---