On the complexity of partial order properties

Abstract

The recognition complexity of ordered set properties is considered, i.e. how many questions have to be asked to decide if an unknown ordered set has a prescribed property. We prove a lower bound of Ω (n²) for properties that are characterized by forbidden substructures of fixed size. For the properties being connected, and having exactly k comparable paris we show that the recogintion complexity is (n:2); the complexity of interval orders is exactly (n:2) -1. Non-trivial upper bounds are given for being a lattice, containing a chain of length k ≥ 2 and having width k.