Multi-tier applications brought several new trends to the software development process. Everyone is now shifting their thinking from good, proven, "old-fashioned" object-oriented design to new component-based design. Component-based design brought a new angle - they (components) should be written based on a particular component standard (COM, JavaBeans, Enterprise JavaBeans, Corba, etc.) and should be pluggable by a tool and/or application. Components not only encapsulate a unit of functionality (like a class in object-oriented design), but also have a discoverable structure/interface used by other components, applications, development tools or component servers.

The benefits of object-oriented design and component-based development:

Reusing software saves money in the development phase of software projects, i.e., the more components you reuse and the less software you have to build. The more applications in which you use a given component, the more valuable that component are. Reusable components enable application developers to customize applications without high costs and long development cycles. Reused software components have fewer bugs because they are used more often, and errors are uncovered and corrected along the way.