LINGUISTIC MODIFIERS: AN OVERVIEW

The power of approximate reasoning is based upon the use of linguistic variables. A variable (e.g. price)is called numeric if its values are numbers (e.g. 5.000 yuan, BEF 100.000, £20.000, 15 Euro,...)and is called linguistic when its values are linguistic terms (e.g. cheap, rather expensive, not expensive but not very cheap either,...). The set of values of a linguistic variable contains at least one primary term (expensive)and most often its antonym or polar opposite (cheap). All the other terms are constructed from these base terms using logical connectives (and, or), negation (not)and linguistic modifiers (rather, fairly, slightly, very,...). The meaning of every term is represented by a Zadeh fuzzy set and can be derived from the fuzzy sets associated with the base terms (i.e. their meaning).