1. Simple 3 layer model From Database to User Interface - Modules © Juhani Välimäki 2004

2. Symbols User Interface module Control module Data storage Simplified 3 layered model No concurrency provided here! (See advanced examples for real multiple client – one server systems.) © Juhani Välimäki 2004

3. Customer records 1313 –port listener JDBC driver DBMS Solid Embedded Engine Solid Flowcontrol TCP/IP interface ResultSet or an int FrCustomer Database ”db” DatabaseControl Customer WinSQL Lite CustomerRecordsApplication (starter, main()) JDBC driverODBC driver Database test workstation SQL-query or update Control © Juhani Välimäki 2004 File ”cust.txt” Business data model FileControl Java API for file handling File-based solution could replace the database solution in some cases. ”Client tier” = UI Client ”Middle tier” = server ”Information tier” = database server WlsWindow (for closing)