InterwikiMap (request via API (http://de.wikipedia.org/w/api.php?action=query&meta=siteinfo&siprop=interwikimap) or on Toolserver-DB) does not list all actually existing Interwiki prefixes.
For parsing wiki source code correctly by bot frameworks it is sometimes important if a link point to an internal or external source.

Examples of Interwikis not shown on interwikimap but working at wmf projects:
[[strategy:]]
[[freenode:#mediawiki]]

Version: unspecified
Severity: major
URL: http://de.wikipedia.org/w/api.php?action=query&meta=siteinfo&siprop=interwikimap