EMSO-definability of some languages with event structures

Languages of words, trees, and pictures with related event structures are considered. An event structure is defined for a word (tree, picture) based on the event structures of individual letters and homogeneous relations between the events of letters on neighboring positions. The main problem considered is the problem of EMSO-definability of two language classes: the class of languages with cyclic event structures and the class of languages with acyclic event structures.