Graphic equality

A relation between two constructive objects (cf. Constructive object) which consists in the fact that the objects are constructed in the same way out of the same elementary tokens. Graphic equality of two words (cf. Word) means that the words are composed of the same letters in the same sequence. Graphic equality of words may more precisely be formulated as follows: a) the empty word is graphically equal to itself only; b) two non-empty words $ P \xi $ and $ Q \eta $( where $ \xi $ and $ \eta $ denote the last letters of these words) are graphically equal if and only if $ P $ and $ Q $ are graphically equal and the letters $ \xi $ and $ \eta $ are identical. Graphic equality is usually denoted by the symbols

$$ = _ \cdot ,\ {\underline \circ } bar . $$

References

[1]	A.A. Markov, "Theory of algorithms" , Israel Program Sci. Transl. (1961) (Translated from Russian) (Also: Trudy Mat. Inst. Steklov. 42 (1954))
[2]	A.A. Markov, N.M. [N.M. Nagornyi] Nagorny, "The theory of algorithms" , Kluwer (1988) (Translated from Russian)