Introduction to Duwamish Books, Phase 3.5: VBA

Ade Miller
Summit Software Company

December 1999

Summary: Provides an overview of the migration of the Duwamish Books sample from Phase 3.5 to 3.5 using Microsoft® Visual Basic® for Applications (VBA). (2 printed pages) Discusses:

• The advantages of using VBA for customization.
  
  
• Extending the Phase 3.5 application's scope using VBA customizations.

Introduction

Phase 3.5 of Duwamish Books showed how a client/server application can be factored across three tiers. Phase 3.5: VBA shows how VBA, a rich customization tool, can be added to such an application to provide customization in the middle tier.

Why VBA?

Microsoft Office 2000 and more than a hundred other applications already use VBA to customize their presentation layer. This phase of Duwamish Books focuses on building VBA customizations as code behind the middle tier using the new multithreaded features of VBA 6.0. These new features readily lend themselves to customizing Microsoft Transaction Server (MTS) components used by Duwamish Books and Microsoft Windows® DNA (http://www.microsoft.com/windowsdna/) applications. Using VBA as your customization tool within a Windows DNA application offers the following benefits:

• VBA is an industry standard. VBA is the Visual Basic-compatible customization language used by Microsoft Office and more than a hundred other shipping applications.
  
  
• Productive development environment. Integrating VBA into your application provides developers with a rich customization experience.
  
  
• Easy to extend VBA functionality. As your application's functionality is factored across multiple tiers in the Windows DNA architecture, so should your customizations. VBA allows you to factor your customizations along with the application:
  • From client to middle tier.
    
    
  • From rich to thin clients. By hosting the customizations in the middle tier business logic exposed to the thin client can also be customized.
    
    
  • From middle tier to disconnected client (using Windows 2000).
• Scalability. VBA code is executed by the VB 6.0 runtime and offers the same scalability.
  
  
• Allows easy customization of business logic components. Each Business Logic Layer (BLL) object exposes an internal programmability model to VBA.

Extending the Application Scope

Duwamish Books, Phase 3.5 represents the sort of turnkey application delivered to satisfy the needs of a particular customer, covering all of their particular requirements. VBA allows a software vendor to ship a product that provides core functionality covering approximately 80 percent of all customers' needs while allowing the final 20 percent of the business solution to be built as VBA customizations.

Duwamish Books, Phase 3.5: VBA demonstrates this approach. Phase 3.5: VBA ships with a customization tool, the Modifier client, which allows additional business logic to be written and deployed on the middle tier using VBA. In this phase of the Duwamish Books sample it should be thought of as a more general package available to other booksellers with their own business requirements. VBA allows the core Duwamish Books application to be customized to suit their individual needs.