Application Servers Page 9
As you go up the complexity scale in Web data -- multiple database servers, distributed applications, Web services, and fat clients -- it becomes increasingly difficult for simple coding with a markup language to manage the data. That's where a relatively new breed of software comes in: the application server. (See our tutorial "Web Servers vs. Application Servers: Making the Right Choice" for more information about app servers.)
Application servers have many functions, but they start with database connectivity and are designed to help organize and control the potentially vast amount of data flowing back and forth from applications, objects, and database servers. These days, application servers from the likes of Borland, IBM, Oracle, and Sun Microsystems also come hitched to massive software development systems (e.g., IBM Websphere Studio) that provide enough tools for even the largest enterprise applications.