Polynomial operations and hierarchies of concatenation (in French)
Theoretical Computer Science
Maximal and minimal solutions to language equations
Journal of Computer and System Sciences
Handbook of formal languages, vol. 1
Context-free languages and pushdown automata
Handbook of formal languages, vol. 1
Handbook of formal languages, vol. 1
Two Families of Languages Related to ALGOL
Journal of the ACM (JACM)
Unification of concept terms in description logics
Journal of Symbolic Computation
Journal of Automata, Languages and Combinatorics - Special issue: selected papers of the second internaional workshop on Descriptional Complexity of Automata, Grammars and Related Structures (London, Ontario, Canada, July 27-29, 2000)
Introduction to Formal Language Theory
Introduction to Formal Language Theory
Theory of Automata
Conjunctive Grammars and Systems of Language Equations
Programming and Computing Software
Conway's problem for three-word sets
Theoretical Computer Science
Information and Computation
Decision problems for language equations with Boolean operations
ICALP'03 Proceedings of the 30th international conference on Automata, languages and programming
The power of commuting with finite sets of words
STACS'05 Proceedings of the 22nd annual conference on Theoretical Aspects of Computer Science
Theoretical Computer Science - Mathematical foundations of computer science 2004
Language equations with complementation: Decision problems
Theoretical Computer Science
On the Computational Completeness of Equations over Sets of Natural Numbers
ICALP '08 Proceedings of the 35th international colloquium on Automata, Languages and Programming, Part II
What do we know about language equations?
DLT'07 Proceedings of the 11th international conference on Developments in language theory
Univariate Equations Over Sets of Natural Numbers
Fundamenta Informaticae
Language equations with symmetric difference
CSR'06 Proceedings of the First international computer science conference on Theory and Applications
Equations x+a=b and (x+x)+c=(x−x)+d over sets of natural numbers
MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
Language Equations with Symmetric Difference
Fundamenta Informaticae - Words, Graphs, Automata, and Languages; Special Issue Honoring the 60th Birthday of Professor Tero Harju
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Unresolved language equations and inequalities with various sets of operations are considered. It is proved that systems of unresolved equations with linear concatenation and union only, as well as systems with linear concatenation and intersection only, are as expressive as the more general unresolved inequalities with all Boolean operations and unrestricted concatenation: the class of languages defined by unique (least, greatest) solutions of these systems is shown to coincide with the families of recursive (RE, co-RE, resp.) sets, which result extends even to individual equations of the form ∪ujXijvj = w∪∪yjXtjzj. On the other hand, unresolved equations with different sets of operations are shown to differ in the hardness of their decision problems, and it is demonstrated that several types of unresolved equations cannot effectively simulate each other in spite of the equality of the language families they define.