The Expense Reporting Tool implements an n-tier application architecture. The user-services tier consists of Microsoft Internet Explorer 4.01 and Microsoft Excel. Users submit information in an Excel document. When the file is saved, a macro parses the data in the .xls file into an Extensible Markup Language (XML) file. Users then navigate to another Web page to upload the XML file onto the Web server. This represents a significant design decision, because the alternative was to run Excel on the server and process the form in the business-services tier. Because it took nearly twenty seconds to process each submission, this design was quickly discarded in favor of the far more scalable design described here.
The business-services tier is composed of Internet Information Server 4.0 running on Windows NT Server and using Active Server Pages as a scripting environment. In addition, four custom COM components run in the Microsoft Transaction Server (MTS) run-time environment. The business-services tier not only exposes functionality to the Web pages that Fitch & Mather employees see, it also uses the components to call ActiveX Data Objects for access to SQL Server, the principal component of the data-services tier.
See Expense Reporting Tool Components for a discussion of the Expense Reporting Tool's component design and deployment in the MTS environment.