- Published 1997

In this paper we describe a general technique for establishing NP-hardness of graph representations. This technique is a generalization of the tool called the logic engine. We show that it is possible to extend it to a wobbly logic engine, which provides a proof method of NP-hardness for a variety of graph representations for which the set of feasible representations does not have to be discrete. This includes representations by visibility and intersection. In particular, we give a rst proof that it is NP-hard to decide whether a graph has a nondegenerate z-axis parallel visibility representation (ZPR) by unit squares.

@inproceedings{EHoule1997TheWL,
title={The Wobbly Logic Engine : Proving Hardness},
author={Michael E.Houle and Sue Whitesides},
year={1997}
}