Rivet Tcl Packages In addition to the core Apache module, Rivet provides a number of Tcl packages that include potentially useful code. dio is a database abstraction layer. form - for creating forms. calendar - a package providing a simple configurable calendar generator rivet entities - an UTF-8 / HTML entities converter formbroker - a form data validators broker ASCII Glyphs - prints most of the ASCII character set as large ASCII art glyphs