dbObjects is a set of components that provide a number of services. These services include user interface (UI) specific operation support, business object operations support, and access to a variety of database sources when working with development environments such as Visual Basic, Microsoft Office products, or Web Applications. Because an object-oriented application design was required and the fact that a majority of client environments would be based on Microsoft Windows, the Component Object Model (COM) from Microsoft was chosen as a basis for the development of dbObjects. In the near future these components will be ported to Microsoft's new .NET framework and a Java-based version of these components will also become available.

A COM component is a unit of executable code, such as an .EXE, .DLL, or .OCX file, that follows Microsoft’s specification for creating and providing access to objects. COM technology allows programmers to assemble these reusable software components into applications and services. COM code components (either .DLL or .EXE) are also known as ActiveX object servers. dbObjects components are constructed as either in-process (.DLL) COM code components, or as out-of-process (.EXE) COM code components. In-process DLL components instantiate objects that run within a client application’s process space and become extensions to the application. Out-of-process EXE components instantiate objects that run within their own process space yet provide services to a client application. Any of the components of dbObjects can be executed locally or across a network through Distributed COM (DCOM) and, in the case of DLL components, in conjunction with Windows 2000’s COM+ applications (same as MTS packages) or for older systems, Microsoft’s Transaction Server (MTS).

dbObjects includes a generic database component (VPDb20.dll) that provides access to a number of Relational database sources as well as MultiValue (PICK) databases. Manipulation of these database sources can be through the execution of stored procedures or direct Structured Query Language (SQL) based access. Database sources include: Microsoft Access, Microsoft’s Database Engine (MSDE), Microsoft Sequel Server, Oracle, Db2, jBASE, D3, mv.BASE, mv.Enterprise, UniVerse, Unidata, and other MultiValue database systems. The VPDb20.dll database component supports multiple APIs (DAO, ADO, and the Vantage mvServer protocol) when accessing database sources. It also supports dynamic runtime binding to data sources for flexible, scalable applications. More will be said about this feature later. The VPDb20.dll component exposes a database object that works closely with Dynamic String Array objects and Data Definition objects from the Power Strings product of VantagePoint Software. This gives the database object direct support for MultiValue data structures to help in application development and operations.

VantagePoint’s dbObjects has a hierarchy of objects that provide database connection and access management, query definition and execution, stored procedure execution, business object definition and operations, and data field processing. These objects, working in conjunction, enable your applications to do the following:

	Dynamically attach to a database source. This enables an application to switch from one database base source to another at runtime without modification.
	Execute parameterized and non-parameterized stored procedures.
	Execute stored procedures that have a return value or that generate a result set of data.
	Construct and execute dynamic SQL queries, both Select and Action queries.
	Generate either Server or Client-side result sets.
	Preserve data integrity with extensive data validation.
	Convert data from input (or stored) formats to display output formats and visa versa.
	Utilize transaction processing (i.e. BeginTrans, Commit, and Rollback) at the application and database level.
	Make and maintain persistent database connections with proper state management.
	Manage concurrency issues (i.e. record locking).
	Through positioned cursors of a result set, add new records and update or delete existing records.
	Operate with a stateless non-persistent database connection for high speed, scalable applications.
	Allow for n-tier application design that distributes processing between the UI, a set of business objects, and a data services tier.
	Distribute business object operations between those that are UI-centric and those that are Data-centric.
	Manage object state between UI-centric and Data-centric objects over a network.
	Supports multiple UI choices such as Win32 applications (VB stand-alone programs), Microsoft Office applications (such as Excel or Word), and Web applications (Active Server Pages, VB Web classes, DHTML applications).
	Cache and reuse database connections when using the stateless non-persistent application model.
	Use a multithreaded Gateway service providing multiplexing techniques for handling large number of concurrent connections, yet minimizing the need for actual database port resources.

The following topics are part of a white paper on the design criteria, features, and operational aspects of dbObjects with a focus on distributed application development. For getting the most out of this information, we recommend that you review this material in the order presented.

Distributed Application Design

dbObjects base classes and templates

Accessing Database Sources

Objects and Services of dbObjects

dbObjects Summary

After reviewing this material you will see that dbObjects is an extensive series of objects and components that work together to provide an effective and scalable framework, meeting the needs of modern distributed application design. dbObjects in conjunction with the mvServer software provide what you need to get the job done and get it done right the first time.

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