Standard wiki URI
In HTML and XML referring to articles in the GFDL text corpus, a standard wiki URI is stated as follows:
protocol://language.service_domain.top_level_domain/wiki/page_name/subpage#section
Only the "/wiki/" is constant. These are relatively easy to remember, e.g. one can easily rattle off URIs of the form http://en.wikipedia.org/wiki/troll where only troll must change to find some other article within en.wikipedia, and where one would be able to simply swap consumerium' for wikipedia to find the equivalent article there, i.e. http://en.consumerium.org/wiki/troll.
Supporting this radically simplifies wiki linking. Unfortunately neither MediaWiki nor GetWiki imposes them as a default. They really should. One theory is that they do not do so because Wikimedia wishes its own URIs to be stable, but those of other users of MediaWiki software to be ever-changing, and thus difficult to remember. This makes it more likely that URIs of Wikipedia pages will be coded into many HTML and XML pages, which helps them advance their claim that they are sole reliable stewards of the GFDL text corpus. GetWiki developers in general resist that claim and are far more likely to implement the standard as a default, and indeed to work towards wikitext standards in general.
See Wikinfo: standard_wiki_URI for more, and interwiki link standard for the equivalent issue for links within the GFDL text corpus.