Algorithm for finding structures and obstructions of tree ideals Original Research Article

Let image be any topological minor closed class of trees (a tree ideal). A classical theorem of Kruskal [Well-quasi-ordering, the Tree Theorem, and Vazsonyiʹs conjecture, Trans. Am. Math. Soc. 95 (1960) 210–223] states that the set image of minimal non-members of image is finite. On the other hand, a finite structural description image is developed by Robertson, et al. [Structural descriptions of lower ideals of trees, Contemp. Math. 147 (1993) 525–538]. Given either of the two finite characterizations of image, we present an algorithm that computes the other.