Divisorial Log Terminal Pair

A divisorial log terminal pair, abbreviated dlt pair, is a log canonical pair admitting a log resolution on which every exceptional prime divisor has strictly positive log discrepancy. The boundary is effective and has coefficients at most one. A log resolution is a proper birational morphism from a smooth variety on which the strict transform of the boundary together with the exceptional divisors has simple normal crossing support. For example, a smooth variety with a simple normal crossing boundary of coefficients in is divisorial log terminal (Kollár and Mori 1998).