Questions tagged [monoid]

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Converting a rational star-connected expression to an NFA

For the free monoid, there is Thompson's construction to convert a rational expression to a 'Non-deterministic' Finite Automaton (NFA). One can regard an NFA as a complex (but powerful) way of ...
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6 votes
1 answer
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star height of star-free languages

I'm interested in the (restricted) star-height of star free-languages. Recalling the definitions: the star height $h(\mathtt{e})$ of a regular expression $\mathtt{e}$ is $0$ if $\mathtt{e}= \...
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5 votes
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Post correspondence problem for finite monoids

The Post correspondence problem has the following version for finite monoids: Input: a finite monoid $M$ and a finite list $(m_1,m_1'),\ldots, (m_n,m_n')$ of pairs of elements of $M$ Question: is ...
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3 votes
3 answers
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Example of monoid $M$ such that $\operatorname{RAT}(M) \not\subseteq \operatorname{REC}(M)$

Let $M$ be a monoid, the family of rational sets $\operatorname{RAT}(M)$ is defined as the smallest set containing the finite subsets, and closed under union, concatentaion and the star operation. The ...
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9 votes
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Generalisation of the statement that a monoid recognizes language iff syntactic monoid divides monoid

Let $A$ be a finite alphabet. For a given language $L \subseteq A^{\ast}$ the syntactic monoid $M(L)$ is a well-known notion in formal language theory. Furthermore, a monoid $M$ recognizes a language $...
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9 votes
1 answer
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Transition monoid membership for DFAs

Given a complete DFA $A=(Q, \Gamma, \delta, F)$, we can define a collection of functions $f_a$ for each $a\in \Gamma$and with $f_a:Q\rightarrow Q$, $f_a(q)=\delta(q, a)$. We can generalize this notion ...
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14 votes
3 answers
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On the realisation of monoids as syntactic monoids of languages

Let $L \subseteq X^{\ast}$ be some language, then we define the syntactic congruence as $$ u \sim v :\Leftrightarrow \forall x, y\in X^{\ast} : xuy \in L \leftrightarrow xvy \in L $$ and the quotient ...
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What is the optimal binary encoding of the elements of a monoid?

The Question Let $M$ be a finite monoid. Let $S$ be a generating set of $M$. Say we have a binary encoding of $S$ represented by $\phi:S \rightarrow A^*$ where $A = \{0, 1\}$. This encoding should ...
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  • 181
9 votes
2 answers
816 views

Formal representation of an abstraction hierarchy

Introduction I'm writing my PhD thesis on Abstract Delta Modeling (ADM), an abstract algebraic description of modifications (known as deltas) able to act on products (as in 'software products'). This ...
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Complexity of Roman numeral evaluation

I came up with a result the other day that arbitrary length Roman numeral evaluation can be modeled as a monoid: https://gist.github.com/4542999 1) Is this a known result? 2) If not, any ...
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