Omer on feature valuation

How can feature sharing be asymmetric?, asks Omer Preminger in a new volume of Papers for David Pesetsky. Omer engages two puzzles for the traditional view that feature valuation is an asymmetric relation, with the features of one item determining those of another: delayed evaluation effects, where two items agree at a point in the derivation where the relevant feature value is not yet available; and privative valuation effects, where the agreed 'value' is the absence of one. He suggests a solution to these puzzles, based on the idea that valuation is the result of a union operation, similar to the set-theoretic union operation but defined, crucially, over geometric feature structures.