This chapter deals with vowel patterns that include identity licensing configurations. Like indirect licensing, such configurations cause a vowel quality in a non-prominent position to also be produced in a prominent position. Unlike patterns with indirect licensing alone, these systems can manifest non-local interactions, where a licensed feature is absent during segments that intervene between the vowel that displays the feature in the licensing position and a vowel that displays the feature in a non-licensing position. Patterns that involve identity licensing can thus be signaled by transparency effects. As discussed in chapter 4, these systems could be expected to include indirect licensing in forms where transparency effects are not applicable. With respect to the vowel whose quality controls assimilation, systems with identity licensing are expected to show similar effects to ones that display only indirect licensing. Patterns where the vowel in licensing position is in control are anticipated to exist by virtue of the strength of this position. Where the controlling vowel is in a non-licensing position, that position is itself expected to be strong in some aspect or an independent factor is expected to be responsible for the vowel's control.
In an identity licensing structure, a vowel quality in a non-prominent position is licensed by a duplicate of the feature in a prominent position. Aspects of the formal approach to these systems are highlighted in what follows. They are characterized by the core ranking in (1).