Implementation
Internally, a wiki that uses interwiki links needs to have a mapping from wiki-code links to full URLs. For example, ] might appear as MeatBall:InterWiki, but link to http://usemod.com/cgi-bin/mb.pl?InterWiki.
Since most wiki systems use URLs for individual pages where the page's title appears at the end of an otherwise unchanging address, the simplest way of defining such mappings is by substituting the interwiki prefix for the unchanging part of the URL. So in the example above, the MeatBall: has simply been replaced by http://usemod.com/cgi-bin/mb.pl? in creating the target of the HTML rendered link.
Rather than creating a new list from scratch for every wiki, it is often useful to obtain a copy of that from another site. Sites such as MeatballWiki and the UseModWiki site contain comprehensive lists which are often used for this purpose - the former being publicly editable in the same way as any other wiki page, and the latter being verified as usable but potentially out of date. MediaWiki's default list of interwiki links is derived from an old version of MeatballWiki's list.
Read more about this topic: Wlink