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Abstract: Context unification is a particular case of second-order unification, where all
second-order variables are unary and only linear functions are sought for as
solutions. Its decidability is an open problem. We present the simplest (currently
known) undecidable quantified fragment of the theory of context unification
by showing that for every signature containing a 2-ary symbol one
can construct a context equation E [p; r; F ; w] with parameter p, first-order
variables r, w, and context variables... (Update)
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BibTeX entry: (Update)
@misc{ vorobyov-equational,
author = "Sergei Vorobyov",
title = "Equational Theory of Context Unification is Hard",
url = "citeseer.ist.psu.edu/article/vorobyov98equational.html" }
Citations (may not include all citations):
105
The problem of solvability of equations in a free semigroup (context) - Makanin - 1977
97
The undecidability of the second-order unification problem (context) - Goldfarb - 1981
23
On equality up-to constraints over finite trees (context) - Niehren, Pinkal et al. - 1997
20
Concatenation as a basis for arithmetic (context) - Quine - 1946
19
Unification of stratified second-order terms (context) - Schmidt-Schau - 1994
19
Simple second-order languages for which unification is undec.. (context) - Farmer - 1991
17
A unification algorithm for second-order monadic terms (context) - Farmer - 1988
7
Coding in the existential theory of concatenation (context) - Buchi, Senger - 1986
6
Studying algorithmic problems for free semi-groups and group.. (context) - Durnev - 1997
2
Positive theory of a free semigroup (context) - Durnev - 1973
1
Undecidability of the positive 89-theory of a free semigroup (context) - Marchenkov - 1982
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