PM alreayd has something like this -- just consider every different wiki out there a different psudoprotocol. Works the same way as what you proposed, except with a :// instead of a :. Is there some other difference I am not seeing? PM's isn't a simple table of templates, but rather a dispatch table, but that allows more complex mappings (which are used in some cases -- for example doc:// acts differently if the argument begins with perl.