PT Admin Application Architecture

The PT Admin application is a three-tier HTML-based intranet application. Technically, it is not a Web-based application because it is implemented and used entirely within the firewall of an organization such as the corporate training center for which the LitWare team designed it.

The following diagram summarizes the architecture of the PT application and identifies the locations of important technologies. To see how this architecture uses a subset of Microsoft technologies for three-tier applications, see CML Architecture.

Location of PT Admin Application Elements

The parts of the PT Admin application are distributed over the three tiers as follows:

• The user-services tier is a rich Web client that users access through Microsoft® Internet Explorer version 5 or later. Internet Explorer 5 natively supports the XML functionality that the PT application requires.
• Logic at the business-services tier runs on the training center's Web server, powered by Microsoft Internet Information Server (IIS) version 4.0 and Microsoft Windows NT® Server version 4.0. The application can also run on Internet Information Services version 5.0, which is included with Microsoft Windows® 2000 Server. For more information about running the PT application on Windows 2000, see Deployment. IIS provides the Internet Services API (ISAPI) and Active Server Pages (ASP) technologies. These technologies process the scripts that generate the application's user interface and create instances of the custom COM components that also run on the business-services tier.
• The data-services tier stores data and provides related services. Within the Microsoft SQL Server™ version 7.0 database reside a number of stored procedures that write and retrieve data to and from the database. You can locate the data-services tier on the same computer as IIS or on a different computer. There are complex issues involved in this decision, including performance, application maintenance, and license agreements that, in the case of BackOffice® Server version 4.5, permit installation on a single computer only. The Deployment node of each BDG scenario addresses some of these issues.