Stationary Move
Definition: Let c, c’ be two configurations of M. Then,  M makes a stationary move from c to c’ according to r, written as c |–S c’ [r] or,
simply, c |–S c’ if
c = xpay,  c’ = xqby and r: pa ® qbS Î R
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Illustration:
Rule: pa ® qbS
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Configuration
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New Configuration
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