Keys to the Enterprise: Data Access Technologies

Steve Apiki

Data access methods like Microsoft's Open Database Connectivity (ODBC) or Apple's Data Access Language provide a common layer over small local databases and server-based SQL engines, but integrating these low-level technologies into a high-level development environment requires additional components. Enter Microsoft's Data Access Objects (DAO) and the Borland Database Engine (BDE).

DAO consists of objects that make up the programmer's interface to Microsoft's Jet engine, the database manager that underlies Microsoft Access and Visual Basic. DAO 3.0, bundled with Visual C++ 4.0, is implemented as a Co mmon Object Model-compliant DLL and works only in 32-bit Windows. It gives fast 32-bit access via Jet to native Access data using the same simple, abstract data objects found in VB. Microsoft Foundation Classes (MFC) 4.0, included in Visual C++ 4.0, wraps DAO objects into C++ classes similar in structure to those that encapsulate ODBC, giving MFC programmers a more-or-less consistent path to both technologies.

Like Jet, BDE is a high-speed database engine and COM object that underlies a collection of development tools and commercial packages (Borland's Delphi, Paradox, dBase, and Quattro Pro), simplifying data sharing. BDE provides access to ODBC and native access to a few SQL databases through Borland's SQL Links.

Using Borland C++ 4.5x, programmers reach these data sources via BDE through C API calls into the BDE DLL (Borland's integrated database API, or IDAPI). Borland C++ 5.0 integrates BDE by wrapping IDAPI calls into C++ classes designed using Delphi' s data object model. Watcom and Symantec provide direct ODBC support through the 16- and 32-bit versions of MFC included with their packages.

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Analogous Architectures

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Borland and Microsoft both use Common Object Model (COM)-compliant components to access their high-speed database engines.