User Extensibility in Amiga Mosaic

Michael Fischer, Michael Meyer, Michael Witbrock


Mosaic and HTTP daemons have greatly improved the utility and aesthetics of the internet by allowing people to express themselves, and to receive and transmit information through a consistent, powerful and attractive interface. There is, however, one important respect in which most current implementations of Mosaic limit user creativity: the program's capabilities are not extensible by the user, except through the relatively awkward addition of external MIME viewers and the use of a simple signal mechanism that allows it to be told to display a new URL. Amiga Mosaic is a widely used version of Mosaic derived from NCSA Mosaic, but not supported by NCSA. It improves on the user extensibility of Mosaic in two ways: it can be completely controlled by external programs and user scripts using the Amiga's standard ARexx Interprocess communication and scripting mechanism; also, using the Amiga's Datatypes object handling system, the user can add new inlined displayable types (such as jpegs, or PICTs) on the fly. By combining these mechanisms, it is possible for Amiga Mosaic to update itself to display new image or sound types, without needing to be recompiled, or even restarted. An explanation of these operating system facilities and their use in Amiga Mosaic will be given, followed by examples of extensions to Amiga Mosaic that have been submitted by the user community. Future extensions, such as inlined sound and video, and self updating pages, that will be supported with these mechanisms will be described.