Universal Data Access is Microsoft's strategy for providing access to information across the enterprise. For more information about Universal Data Access, see the site http://www.microsoft.com/data.
In a Windows DNA n-tier application, data access components cross the boundary between the business-services tier and the data-services tier. These components, such as ActiveX Data Objects (ADO), are called from the custom business objects that run in the Microsoft Transaction Server environment.
The Universal Data Access-based framework operates at two levels within an application. At the systems level, OLE DB defines an architecture specified as a set of COM-based interfaces that encapsulate various database management system services. The OLE DB architecture does not constrain the nature of the data source.
At the application level, ADO provides a high-level interface to enable developers to access data from any programming language.
The Microsoft Open Database Connectivity (ODBC) interface is an industry standard. The ODBC interface enables applications to access data from a variety of database management systems. ODBC permits maximum interoperability—an application can access data in diverse database management systems through a single interface. Furthermore, that application will be independent of any database management system from which it accesses data. Users of the application can add software components, called drivers, that create an interface between an application and a specific database management system.
ADO, OLE DB, and ODBC together make up the Microsoft Data Access Components (MDAC). MDAC is part of the Microsoft Data Access SDK, which is integrated into the Platform SDK. For more information, see "Data Access Services" in the Platform SDK.
There are other technologies you can use to call into the data-services tier from the business-services tier. As described previously, MSMQ calls into message queues to send or receive messages between applications asynchronously. Collaboration Data Objects, a high-level component-based scripting interface, allows you to call into Microsoft Exchange databases to build e-mail and other collaboration functionality into your applications. Active Directory Service Interfaces enables you to access and manage resources throughout a distributed network environment, allowing you to locate users, computers, printers, and information about them stored anywhere on the network.