I've never found it to be a problem since the rules are the same between the languages (whereas other languages, like Korean, Japanese, etc have different language rules so separate lexers are appropriate). If using a thesaurus, you'll obviously want to make certain you have the correct terms. I almost always use a custom stoplist as well, so add any custom terms to the standard 'of', 'the' list of stopwords.
Is there a particular feature of Oracle Text that you were most concerned about, or is your inquiry more of a high-level question? If you are planning on supporting a global app, take a look at the multi_lexer or world_lexer (depends on your version whether the world_lexer is available).
We are implementing a system in Australia that will be used by school children, between ages 6 - 18. The problem
is spelling of certain words. For example, American
english spells Organization, while Australian english
spells it Organisation.
Since this will be a teaching and learning system,
we do not want to encourage incorrect spelling of words!
A thesaurus can provide even more assistance if you are indexing American English but wish to search using the Australian version of terms and stemming or fuzzy searching isn't cutting it. For example, if your docs use the term widget, but you want to search on gadget, you can use a thesaurus.
Keep in mind that the lexer's job is to break your text into tokens. It doesn't alter your text. Since the rules between different flavors of English are the same, then you won't have a problem. The lexer will still break the text into tokens, and the original 'organisation' will still be spelled 'organisation'. Text offers alternate methods of search, and some add-on capabilities such as theme generation, but your original text is not altered.
You can see this in the example I showed you by examining the DR$TEST_IDX$I.TOKEN_TEXT column. Query the column and you will see the tokens created.