On a raw December day, as Christmas music blares over loudspeakers, an African elephant named Asha walks in tight circles in an enclosure at Natural Bridge Zoo, a roadside attraction in Virginia. Her living quarters consist of a barn and three outdoor yards--a fenced patch of grass about 90 by 40 feet, a dirt patch with a few logs scattered about, and a yard where she gives rides to children for $15 and her massive feet have worn a ring into the grass. Her space is barren--no shrubs, trees, or watering holes. Elephants, like humans, are social animals. In the wild, females typically live in herds of eight or more, yet Asha, who's nearly 40 years old, has been confined mostly alone for more than 30 years.

Inconsistencies between different information sources may arise because of statements that are inaccurate, albeit not completely false. In such scenarios, the most natural way to restore consistency is often to interpret assertions in a more flexible way, i.e. to enlarge (or relax) their meaning. As this process inherently requires extra-logical information about the meaning of atoms, extensions of classical merging operators are needed. In this paper, we introduce syntactic merging operators, based on possibilistic logic, which employ background knowledge about the similarity of atomic propositions to appropriately relax propositional statements.