Variant generation operates on the assumption that the target string to be substituted can be completely replaced by another, regardless of context. The rules can include removing or including the accents in a query term, or modifying the suffix of a query term.
Each substitution causes a variant form to be added to the search along with the original search term. For example, given a rules file which specified replacement of every e by the three accented forms é, ê, and è, the original word donne would generate a search for donne, donné, donnê, and donnè. A replacement string cannot be modified by another rule.
The maximum number of rules per file is 40, and a maximum of 30 substitutions can be applied simultaneously to a given word. If one of these limits is exceeded, FTR rejects the query. If the format of a rule does not conform to the syntax specified in Syntax and Semantics of the Rules File, FTR could reject the query.