(:Summary: Interwiki links definition and use:)
(:Audience: author (intermediate) :)

The InterMap (also called InterWiki in some other wikis) is a system for defining links between [[WikiWikiWeb]] sites that was first developed by UseMod:UseModWiki and Meatball:MeatballWiki.  The method is to use a word that stands for a path that is defined. InterMap links have the form [@MapPrefix:PagePath@], where the host prefix is converted to a partial URL based on entries in the site's ''intermap.txt'' and ''localmap.txt'' files.

[[#custominclude]]
The default ''intermap.txt'' distributed with PmWiki (in the ''scripts/'' directory) includes the following InterMap entries:
>>pre<<
 PmWiki:     http://pmwiki.org/wiki/PmWiki/ 
 Cookbook:   http://pmwiki.org/wiki/Cookbook/ 
 Wiki:       http://c2.com/cgi/wiki? 
 UseMod:     http://usemod.com/cgi-bin/wiki.pl? 
 Meatball:   http://usemod.com/cgi-bin/mb.pl? 
 Wikipedia:  http://wikipedia.com/wiki/ 
 PITS:       http://pmwiki.org/PITS/ 
 Path:
>><<

(:if exists {$SiteGroup}.InterMap:)
[[{$SiteGroup}.InterMap]] includes the following entries:
(:include {$SiteGroup}.InterMap#include#includeend:)
(:else:)
You can map your own prefixes in your local page [[{$SiteGroup}.InterMap]].
(:ifend:)
[[#customincludeend]]

Thus, "PmWiki:Variables" becomes "http://pmwiki.org/wiki/PmWiki/" + "Variables," a link to the [[PmWiki.Variables->http://pmwiki.org/wiki/PmWiki/Variables]] page on the official PmWiki web site, Wiki:FrontPage is a link to the front page of the first WikiWikiWeb, and Wikipedia:Stonehenge takes you to the Wikipedia article about the famous megaliths in England.  

Like other links, you can use the double-bracket syntax to get different link text:
(:markup class=horiz:)
* [[Meatball:StartingPoints | starting points]] over at Meatball
* [[starting points -> Meatball:StartingPoints]] over at Meatball
(:markupend:)

If you want to link just to what the intermap says (e.g. http://wikipedia.com/wiki/ for Wikipedia), then do [@[[Wikipedia:. | Wikipedia's main page]]@], which produces [[Wikipedia:. | Wikipedia's main page]].  Note the . (period) after the Map: reference.

[[#path]]
The special [@Path:@] InterMap entry can be used to create "[[Cookbook:RelativeUrls|relative urls]]" in [[Cookbook:RelativeLinks|links]].

The actual set of InterMap links at any site is defined by the site administrator via the [[Site.InterMap]] page and the ''local/localmap.txt'' file; for more details, see [[PmWiki.CustomInterMap]]s.