( ( A ( turing machine ) ) ( ( is ( ( a ( simple ( theoritical machine ) ) ) ( that ( should ( be ( able ( to ( ( solve ( any problem ) ) ( that ( ( a ( ( more complex ) machine ) ) ( ( ( ( ( can , ) and ) hence ) , ) ( is ( used ( in ( proofs ( on ( complexity theory ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (VBG turing) (NN machine)) (VP (VBZ is) (NP (NP (DT a) (JJ simple) (JJ theoritical) (NN machine)) (SBAR (WHNP (WDT that)) (S (VP (MD should) (VP (VB be) (ADJP (JJ able) (S (VP (TO to) (VP (VB solve) (NP (DT any) (NN problem)) (SBAR (IN that) (S (NP (DT a) (ADJP (RBR more) (JJ complex)) (NN machine)) (VP (VP (MD can)) (, ,) (CC and) (ADVP (RB hence)) (, ,) (VP (VBZ is) (VP (VBN used) (PP (IN in) (NP (NP (NNS proofs)) (PP (IN on) (NP (NN complexity) (NN theory)))))))))))))))))))) (. .)))
A turing machine is a simple theoritical machine that should be able to solve any problem that a more complex machine can, and hence, is used in proofs on complexity theory.
(ROOT (S (S (NP (DT A) (JJ complex) (NN machine)) (VP (VBZ is) (VP (VBN described) (PP (IN by))))) (: :) (S (NP (PRP it)) (VP (VBZ is) (VP (VBN made) (PP (IN of) (NP (QP (JJR more) (IN than) (CD one)) (JJ simple) (NN machine)))))) (. .)))
A complex machine is described by: it is made of more than one simple machine.