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A Characterization of Comparability Graphs and of Interval Graphs

1964/01/01 by Paul C. Gilmore, Alan J. Hoffman · 23 citations
Computer Science · Mathematics · #semigroups and automata theory #Advanced Graph Theory Research #Formal Methods in Verification #Mathematics #Comparability #Combinatorics #Comparability graph #Discrete mathematics #Interval graph #Characterization (materials science) #Graph #Pathwidth #Line graph

paper · pdf · doi:10.4153/cjm-1964-055-5

openalex publication_date 1964/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04

Abstract

Let < be a non-reflexive partial ordering defined on a set P . Let G ( P , <) be the undirected graph whose vertices are the elements of P , and whose edges ( a , b ) connect vertices for which either a < b or b < a . A graph G with vertices P for which there exists a partial ordering < such that G = G ( P , <) is called a comparability graph. In §2 we state and prove a characterization of those graphs, finite or infinite, which are comparability graphs. Another proof of the same characterization has been given in (2), and a related question examined in (6). Our proof of the sufficiency of the characterization yields a very simple algorithm for directing all the edges of a comparability graph in such a way that the resulting graph partially orders its vertices.

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