Acronimo 3TIER

Abstract After the years of terminal/mainframe solutions, the client/server architecture in gen-eral has become the architecture of choice for many applications because it has repre-sented the opportunity to split the processing load and, through the clear hardware and software distinction between client and server, was able to raise the end-user expecta-tions about interface. The trend during the last years is towards different client/server forms: 3-tier and, more generally, N-tier architectures. The multi-tier model foresees a split between an interface layer (presentation layer) and a business logic layer (domain layer), creating the need for a middle-tier, responsible for the interaction between application and database. The need of a 3-tier model has been accentuated by the strong use of the Web, which has led the software from departmental solutions to world-wide ones. In fact current implementations of Web based business applications are centered around the 3-tier model (even called 2.5-tier model). The application is organized in 3 layers. At the top is the presentation layer which runs on the Web cli-ent and is often implemented as an HTML forms based GUI with provisions like cookies for emulating sessions. On the servers side, the middle and bottom layers implement the domain specific and the data persistency logic (data layer) respec-tively. There is a natural tendency to come away from these often primitive HTML GUIs in favour to richer Java based presentation layers. However, Java applets, like any mod-ern GUIs, can become quite complex. Complexity often resides in the strong interac-tions between widgets and between these and the domain layer. The usual approach of building the presentation layer completely in Java lessens the chance of applet reuse because of the strong coupling between the widgets and the presentation logic that glues them together.

Enti SUPSI coinvolti Laboratorio sistemi informativi e ingegneria del software

Responsabili Sandro Pedrazzini

Data di inizio progetto 1 giugno 1999

Data di chiusura progetto 1 maggio 2000