Starting with version 6.2, IDL is distributed directly with HTML online help, and an XML-based catalog of routine information. This makes scanning the manuals with the tool get_html_rinfo, and the idlw-rinfo.el file it produced, as described here, entirely unnecessary. The information is left here for users wishing to produce a catalog of older IDL versions' help.
IDLWAVE derives its knowledge about system routines from the IDL manuals. The file idlw-rinfo.el contains the routine information for the IDL system routines, and links to relevant sections of the HTML documentation. The Online Help feature of IDLWAVE requires HTML versions of the IDL manuals to be available; the HTML documentation is not distributed with IDLWAVE by default, but must be downloaded separately.
The HTML files and related images can be produced from the idl.chm HTMLHelp file distributed with IDL using the free Microsoft HTML Help Workshop. If you are lucky, the maintainer of IDLWAVE will always have access to the newest version of IDL and provide updates. The IDLWAVE distribution also contains the Perl program get_html_rinfo which constructs the idlw-rinfo.el file by scanning the HTML documents produced from the IDL documentation. Instructions on how to use get_html_rinfo are in the program itself.