Must be stated that the structure as a such, be studied very little, and if so, then either very generally or linked to specific objects. The structure is an integral attribute of all discrete phenomena, their constructional or organizational side. Unfortunately, the concept of structure has devalued to a vague adjective of all objects. In an attempt to explain the essence of structure, we proceed from the fact that the structure is given as a graph and isomorphic graphs have the same structure. However, the structure is something qualitative which with only quantitative graph-theoretical tools is not considered. It has been shown that the essence of structure consists in the relationships between its elements, and it has created a need to look the ways for presenting these relationships. Here is presented a way for recognition of the structure with exactness up to isomorphism and other structural properties. It is implemented in the form of a semiotic model that enables to explain the essential properties of structure and their transformations.