Matt England wrote:

On my MediaWiki 1.4.0 system,

You should probably upgrade to 1.4.4, which includes a number of bug fixes.

I notice that a search for "plan" does not match text or titles with the word "plans" (among other similar mismatches).

That's normal.

Can I change this behavior (such that "plan" will match "plans") in my 1.4.0 system? In not, do later MediaWiki versions address this and/or might future MediaWiki version support this feature? Is there an advanced-search feature available in 1.4.0 or later/future versions?

You could try to hack in stemming to the indexing if you really want. (See the Language class for search index word normalization routines.)

If you use the experimental external Lucene-based search engine it will use a stemmer for English by default. This requires that you know what you are doing and have sufficient resources and access to run a separate Java or Mono-based server program.

-- brion vibber (brion @ pobox.com)