Abstract
Every graph property expressible in monadic second-order (MSO) logic, can be
checked in linear time on graphs of bounded tree-width by means of finite automata
running on terms denoting tree-decompositions. Implementing these automata is
difficult because of their huge sizes. Fly-automata (FA) are deterministic automata
that compute the necessary states and transitions when running (instead of looking
into tables); they overcome this difficulty. Previously, we constructed FA to check
MSO properties of graphs of bounded clique-width. An MSO property with edge
quantifications (called an MSO2 property) is an MSO property of the incidence
graph and, graphs of tree-width k have incidence graphs of clique-width O(k). Our
existing constructions can be used for MSO2 properties of graphs of bounded treewidth.
We examine concrete aspects of this adaptation.