| Issue |
RAIRO-Theor. Inf. Appl.
Volume 42, Number 3, July-September 2008
JM'06
|
|
|---|---|---|
| Page(s) | 583 - 598 | |
| DOI | https://doi.org/10.1051/ita:2008020 | |
| Published online | 03 June 2008 | |
On Varieties of Literally Idempotent Languages
Department of Mathematics, Masaryk University,
Janáčkovo nám 2a, 662 95 Brno, Czech Republic; polak@math.muni.cz
A language L ⊆A* is literally idempotent in case that
ua2v ∈ L if and only if uav ∈ L, for each u,v ∈ A*, a ∈ A.
Varieties of literally idempotent languages result naturally by taking
all literally idempotent languages in a classical (positive) variety
or by considering a certain closure operator on classes of languages.
We initiate the systematic study of such varieties. Various classes of
literally idempotent languages can
be characterized using syntactic methods.
A starting example is the class
of all finite unions of 
where B1,...,Bk are
subsets of a given alphabet A.
Mathematics Subject Classification: 68Q45
Key words: Literally idempotent languages / varieties of languages.
© EDP Sciences, 2008
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