Large-Scale ASP Replication of Database-Driven Portals

Abstract

More and more companies and organizations are discovering the benefits of providing services over the Internet through portal applications. In order to provide a more profitable, responsive, and flexible user experience, these portal applications and services generate responses dynamically and provide a customizable experience for each user. That is, the content they provide to the user is generated on demand in response to user requests. These applications usually have two components: (1) front-end business logic that interacts with the user and provides the portal's look and feel and (2) a back-end database or databases containing the portal's true content Li, Hsiung, Po, Hino, Candan, & Agrawal, 2004b;Vallamsetty, Kant, & Mohapatra, 2002). Based on user requests the frontend logic queries the back-end databases, obtains needed content, and then uses that content to build a page (or other result) which is returned to the user. Figure 1(a) shows a diagram of a complex database-driven portal application while Fig. 1(b) shows a simplified version containing the main components: the application logic and backend database. As will be explained later, the back-end database is important. To emphasize that importance such portal applications will be henceforth called database-driven applications, or DAs. KEY TERMS AND THEIR DEFINITIONSDatabase-driven portal application. A web-based application consisting of business logic and a (usually) large database or database containing the application's content. In response to user requests, the logic queries the database, obtains needed content, and then uses that content to build a page (or other result) which is returned to the user. In this article, "portal", "portal application", "databasedriven portal application", and "database application (DA)" are synonymous.Replication. Making multiple copies of something in order to increase access to it. Quality-differentiated portal application.A portal application that can store data and make its responses available in multiple temporal freshness levels.Application Service Provider (ASP). A portal hosting service. In this article, ASPs are presumed to specialize in the hosting and replication of DAs.ACDN. Active Content Deliver Network (ACDN) is a management system for the replication of DAs. DATE.Database-driven Application AssignmenT Engine (DATE) is software program that makes replica-to-server assignments for multiple quality-differentiated DAs. The assignments meet user demand and minimize replication overheads. DASIM.The Database Application System Implementer and Manager (DASIM) is a prototype database application replication environment.