Net.Data is designed to allow new programming language and database interfaces to be added in a pluggable fashion. These interfaces are called language environments and are accessed as DLLs or shared libraries. Language environments provide access to applications and databases that support your dynamic Web pages. By invoking language environments with function calls and SQL statements, you can access the functions and utilities that these language environments provide for use with your business application. For example, you can directly access your ODBC database, use the Perl language environment to call Perl scripts, or call the Java Applets language environment to run Java applets.
The Net.Data initialization file associates each language environment name with a DLL or shared library. Each language environment must support a standard set of interfaces defined by Net.Data. Net.Data loads the DLL or shared library specified in the initialization file the first time that a function call for a FUNCTION block specifying that language environment is encountered.
Net.Data parses the Net.Data macro, maintains the Net.Data variables, communicates with the language environments, and formats the output according to the REPORT and MESSAGE block specifications. The language environment supports the interfaces defined to Net.Data, makes the Net.Data parameters accessible to the language processor in some language-dependent manner, calls the language interpreter, and receives the variables back from the language interpreter in some language-dependent manner.
Figure 1 demonstrates Net.Data's interaction with language environments.
Figure 1. Net.Data and Language Environments
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Working with language environments in a Net.Data application involves two kinds of tasks.
This book is organized to help you with both tasks: