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17. What role do middleware standards like ODBC, JDBC, OLE-DB and ADO play in creating dynamic web pages?

Data access middleware is what connects a web server to back-end data resources such as relational tables, flat files, e-mail messages, directory servers, etc. While this sounds complicated (and often is), it can be as simple as serving up a web page populated with data from a local comma-delimited file.

The Open DataBase Connectivity (ODBC) standard was developed by Microsoft to give programmers a uniform, SQL-based interface to different relational databases. Despite its complexity ODBC has been wildly successful and is very widely supported, but it performs poorly relative to vendor-specific ("native") drivers, making it unsuitable for heavily loaded applications.

The Java DataBase Connectivity (JDBC) standard was developed by Sun Microsystems' JavaSoft division to give Java programmers a uniform interface patterned after ODBC to different databases. Successful because of its platform independence, JDBC suffers from performance problems similar to ODBC.

OLE-DB is Microsoft's emerging component database architecture, the data modeling side of its COM strategy. Whereas ODBC was a uniform interface to relational data, OLE-DB aims to provide universal access to all types of information, whether stored in RDBMS, VSAM, IMS, Active Directory Services, message stores, or any other format for which Microsoft or a third party writes an OLE-DB Provider.

ActiveX Data Objects (ADO) is a practical web-based interface for implementing OLE-DB connectivity. While it is possible to code directly to the OLE-DB infrastructure using VC++ or Java, Microsoft expects the majority of developers to use ADO, which as an ActiveX component can be accessed from any language that supports COM.

Furthermore, ADO is optimized for web applications. Through the judicious use of client-side caching and session identifiers, ADO emulates state management. The upshot is that ADO applications should perform on the Internet nearly as well as LAN-based client/server systems did on proprietary networks.