HydraExpress provides three primary libraries: a Web service library that supports Web service and client development; an XML binding library that supports extension of the generated XML binding interface; and a servlet library that supports servlet development. There are additional libraries that mainly support internal implementation, but that may be needed at times when writing extensions. The full public API is documented in the HydraExpress C++ API Reference Guide.

Header files for these libraries are located in the directory <installdir>\include\rwsf\ as follows:

The HydraExpress lib directory contains release and debug versions of all libraries. Release libraries are marked as 12d, debug libraries as 15d. When you build a HydraExpress project, the 12d libraries are used by default and the project includes a 12d directory that contains artifacts from the release build.

The 15d libraries allow you to build projects in debug mode. The project then builds in debug mode and includes a 15d directory that contains artifacts from the debug build.