E. I. Vatutin, I. V. Zotov, V. S. Titov
In the paper, the problem of searching for isomorphic inclusions of R-expressions that arises while constructing a set of sections in the decomposition of parallel logic control algorithms is solved. A method for solving the problem is proposed which is capable of polynomial search for ismorphic substitutions on a tree-based representation of R-expressions. The method is shown to be sorrect based on a number of theorems proving that there exists the only isomorphic inclusion. Well-dnown analogous methods applicable to general case graphs are dnown to belong to the NP class. Our method may be extended to other similar problems, e. g., those solved by optimizing compilers.