Generalised dualities and maximal finite antichains in the homomorphism order of relational structures

The motivation for this paper is three-fold. First, we study the connectivity properties of the homomorphism order of directed graphs, and more generally for relational structures. As opposed to the homomorphism order of undirected graphs (which has no non-trivial finite maximal antichains), the order of directed graphs has finite maximal This research was partially supported by the EU Research Training Network COMBSTRU. The third author's research is supported by grants from NSERC and ARP. The Institute for Theoretical Computer Science is supported as project 1M0021620808 by the Ministry of Education of the Czech Republic. 1 

• Type: Journal
• Year: 2008
• Where: EJC
• Authors: Jan Foniok, Jaroslav Nesetril, Claude Tardif
• Keywords: EJC 2007, EJC 2008, Finite Maximal Antichains, Homomorphism Order, Information Technology, Maximal This Research