Slides.

STEPHAN KREUTZER COMPLEXITY OF MODEL-CHECKING PROBLEMS 65/81
INTRODUCTION COMPLEXITY UPPER BOUNDS COMPOSITION LOCALITY LOCALISATION GRIDS GRID-LIKE MINORS LABELLED WEBS
Minors
Definition. A graph H is a minor of G, denoted H ≼ G, if it can be obtained
from a subgraph G ′ of G by contracting edges.
Equivalently. H ≼ G if for every v ∈ V(H) there is a connected G v ⊆ G such
that
• if u ≠ v ∈ V(H) then G u ∩ G v = ∅ and
• if {u, v} ∈ E(H) then there is an edge in G joining G u and G v .