o Most J2EE web-based enterprise applications are split into three logical tiers, Presentation Tier, Business Logic Tier, and Enterprise Information System Tier. The presentation tier, which aims at presenting the business information to the user, is implemented using Servlets, JSPs and HTML/WML. The business tier, where core business mechanisms are implemented, is usually encapsulated in EJBs (Enterprise Java Beans). The enterprise information system tier, which represents different kinds of legacy systems, database servers, etc is usually accessed through the JDBC API and other standard interfaces provided by the J2EE Connector Architecture.