Complexity of E0L Structural Equivalence

  title={Complexity of E0L Structural Equivalence},
  author={Kai Salomaa and Derick Wood and Sheng Yu},
  journal={RAIRO Theor. Informatics Appl.},
We show that the EOL structural equivalence problem is logspace hard for deterministic exponential time. Also, we show that this question can be solved in linear space by a synchronized alternating Turing machine, and thus establish an exponential space upper bound for its complexity. The equivalence of finite tree automata is shown to be logspace reducible to context-free structural equivalence. The converse reduction is well known and thus context-free structural equivalence is complete for… 
On Computational Complexity of Basic Decision Problems of Finite Tree Automata
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For a given context-sensitive grammar G we construct ET0L grammars G 1 and G 2 that are structurally equivalent if and only if the language generated by G is empty, which implies that structural
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Decidability of Structural Equivalence of E0L Grammars
Deciding Equivalence of Finite Tree Automata
  • H. Seidl
  • Computer Science
    SIAM J. Comput.
  • 1990
For finite tree automata with coefficients in a field R, a polynomial time algorithm is given for deciding ambiguity-equivalence provided R-operations and R-tests for 0 can be performed in constant time.
Structural Equivalence and ET0L Grammars
Structural Equivalence and ETOL grammars
It is shown that structural equivalence is undecidable for propagating ET0L grammars even when the number of tables is restricted to be at most two, in contrast to the decidability result for the E0L case.
Defining families of trees with E0L grammars
The Complexity of the Emptiness Problem for EOL Systems
The emptiness problem for EOL systems is shown to be computationally equivalent to the word problem of RPAC automata which are augmented with a LOGSPACE working tape and a two-way input head.
The Tape-Complexity of Context-Independent Developmental Languages
  • J. V. Leeuwen
  • Computer Science, Linguistics
    J. Comput. Syst. Sci.
  • 1975
Simplifications of E0L Grammars
It is established that some simplification results for E0L grammars that preserve their structure are sufficient to solve the structural equivalence problem, but this does not hold in the context-free case.
A normal form for structurally equivalent E0L grammars
A normal form for structurally equivalent E0L grammars is constructed. Two E0L grammars are structurally equivalent iff the respective normal form grammars are isomorphic. This result gives also a