Abstract
Tesar (2014) develops the notion of output-drivenness, provides guarantees that Optimality Theory grammars satisfy it, and demonstrates its learnability implications. This article discusses the extension of Tesar’s theory to a representational framework with partial phonological features. It considers a hierarchy of notions of output-drivenness of increasing strength that can be defined within this extended framework. It determines the strongest notion of output-drivenness that holds in the case of partial features. And it shows that the learnability implications discussed by Tesar carry over to a framework with partial features only if feature undefinedness is effectively treated by identity faithfulness constraints as an additional feature value.