Technical Reports

The report FIMU-RS-99-01

On the Pattern Equations

by Ivana Èerná, Ondøej Klíma, Jiøí Srba, This is a full version of the paper accepted to SOFSEM`99. July 1999, 11 pages.

FIMU-RS-99-01. Available as Postscript, PDF.

Abstract:

Word equation in a special form X=A, where X is a sequence of variables and A is a sequence of constants, is considered. The problem whether X=A has a solution over a free monoid (PATTERN EQUATION problem) is shown to be NP--complete. It is also shown that disjunction of a special type equation systems and conjunction of the general ones can be eliminated. Finally, the case of stuttering equations where the word identity is read modulo xx=x is mentioned.