Program semináře
2022
2020
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Podrobný program -
zde (přednášky vedeny v angličtině)
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dr. Pavel Martinek: Multiset Languages and Minimization Problem for Multiset Finite Automata
Abstract:
Multisets (also called bags) represent such a generalization of sets which allow multiplied occurrence of their elements. Finite automata working over multisets differ from usual finite automata in the way how they process their input. Namely, at each computational step, they read a symbol from their input multiset regardless of any ordering of the input. Thus, instead of processing strings of symbols the automata process multisets of symbols. This formalism was already used in defining computational models inspired from biochemistry (like the chemical abstract machine by Berry and Boudol, 1992) or biology (cf. well-known P systems). It has also strong connections to jumping automata introduced by Meduna and Zemek in 2012.
The aim of the talk is to describe the concept of multiset automata and their place in formal languages theory, to show their similarities and dissimilarities with classical and jumping finite automata and to deal with minimization of these automata.
2019
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Podrobný program -
zde (přednášky vedeny v angličtině)
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Abstract:
It is well known that the set of context-free languages is a strict subset of the set of recursively enumerable languages. Analogously, a type-2 (or context-free) grammar cannot simulate a type-0 grammars. However, if we control or regulate the application of the context-free rules, then we can make the grammar to simulate a type-0 grammar. Several regulations are associated with these grammars and are called regulated rewriting grammars. Some of them are (i) Matrix rewriting grammars (ii) Graph-Controlled grammars (iii) Semi-Conditional grammars. The descriptional complexity investigates the economical measures required for a grammatical device, automaton, or a rewriting system for a succinct representation of a formal language class.
In this talk, we are going to concentrate on semi-conditional grammars and their variants simple semi-conditional and generalized forbidden grammars. In a semi-conditional grammar, the derivations are controlled by permitting string and/or forbidden string that are associated with each rule and is known as conditional rule. The maximum lengths of permitting strings of permitting and forbidden strings refer to the degree of the system. Besides degree, the number of nonterminals and the number of conditional rules are considered to be descriptional complexity measures. We will see the computational completeness results of the above said systems with minimal/succinct sizes of measures. Our proofs include some novel ideas and effective use of Geffert normal forms. In the sequel, we will review some results available in the literature; many of the results are contributed by Prof. Alexander Meduna and his research group.
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Lakshmanan Kuppusamy: Descriptional Complexity of Matrix and Graph-Controlled Insertion-Deletion Systems
Abstract:
Lila Kari introduced the Insertion-deletion system (abbreviated as ins-del system) in formal language theory. Informally, the insertion and deletion operations are defined as follows: if a string w is inserted between two parts u and v of a string uv to get uwv, then we call the operation insertion, whereas if a substring x is deleted from a string uxv to get uv, then we call the operation deletion. Suffixes of u and prefixes of v are called left and right context, respectively. An ins-del system is well described by its size, denoted by (n, i′, i′′; m, j′, j′′) where the parameters from left to right denote (i) the maximal length of the insertion string, (ii) the maximal length of the left context in insertion rules, (iii) the maximal length of the right context used in insertion rules, (iv)-(vi) denote the similar things in deletion rules.
Computational completeness for ins-del systems can even be achieved with rule size (1,1,1; 1,1,1) but with no rule size strictly smaller than this. This fact has motivated to study ins-del systems in combination with regulation mechanisms and to achieve the computational completeness with smaller/trade-off size than (1,1,1; 1,1,1). Some of the important variants of ins-del systems are graph-controlled ins-del (GCID) systems, matrix ins-del (MID) system. In matrix ins-del system, the rules are in the form of a matrix and a matrix is a set of ins-del rules. During the derivation, if a matrix is chosen, then all the rules of the matrix are applied in sequentially and in order to the derived string. In graph-controlled ins-del system, there are several components and each component has a set of rules. A transition is performed on the string based on any applicable rule in the current component and the resultant string is moved to the target component specified in the rule itself.
In this talk, we see some computational completeness results of matrix and graph-controlled ins-del systems, reducing the ID size, say, to (1,1,0,1,1,0) at the expense of increasing other measures of descriptional complexity. If time permits, we will also see representation of linear languages using these systems with their descriptional complexity measure sizes.
18. 12. 2019, 11:00 - 12:00, E112, FIT VUT, Božetěchova 2, Brno
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Abstract:
In formal language theory, when we study new models, we often want to know whether a certain language can be defined by the model in question. To show that it is possible, we can simply construct an appropriate instance of such a model. However, to show that it is not possible, we have to rigorously prove that no such an instance can exist. If we want to show that a language cannot be defined by the given model and we work with finite or context-free languages, we can use pumping lemmas which are specifically constructed for this task.
Nonetheless, when we work with jumping models, it is usually not possible to easily derive such a lemma. Luckily for us, we can usually exploit the fact that jumping models cannot sufficiently control the order of symbols and show that if the model defines some word in the language it also has to define some word that is not in the language. However, in the newly introduced jumping 5'→3' Watson-Crick finite automata this previous approach can no longer be effectively used since the model can easily keep the precise order of symbols for all linear languages.
In this talk, we introduce a new concept of the debt of the configuration of the automaton and show how it can be used to prove that a language cannot be defined by the given jumping model.
2018
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Podrobný program -
zde (přednášky vedeny v angličtině)
6. 12. 2018, 11:00 - 11:30, A112, FIT VUT, Božetěchova 2, Brno
Radim Kocman: A Jumping 5'→3' Watson-Crick Finite Automata Model
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Abstract: This talk will introduce jumping pure grammars, which are conceptualized just like classical pure grammars except that during the applications of their productions, they can jump over symbols in either direction within the rewritten strings. We will compare the generative power of jumping pure grammars with that of classical pure grammars while distinguishing between their versions with and without erasing productions. Apart from sequential versions, we will present an analogical study in terms of parallel versions of jumping pure grammars represented by 0L grammars. During the talk, several open problems will be introduced to suggest the future investigation of jumping pure grammars.
2017
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Podrobný program -
zde (přednášky vedeny v angličtině)
22. 11. 2017, FIT VUT, Božetěchova 2, Brno
Wednesday, November 22, 2017, 13:00 - 13:50, room
E112:
Dr. Benedek Nagy: Linear context-free languages and Watson-Crick automata
Abstract: Watson-Crick automata are inspired from the Nature, as instead of a normal tape, a Watson-Crick tape, i.e., a DNA molecule is considered as input. A DNA molecule has two strands, subsequently Watson-Crick automata have two reading heads, one for each strand. DNA strands have orientation, the 5'→3' direction is preferred in some biochemical reactions. In 5'→3' Watson-Crick automata the two reading heads start from the two extremes of the input (the opposite ends of the molecule) and finish the process when the heads meet. With 5'→3' Watson-Crick finite automata the class of linear context-free languages can be accepted, and some of its subclasses by some restricted variants. Deterministic variant characterizes a proper subset of linear languages, the class 2detLIN. This class is incomparable with the traditional detLIN, the class of languages that can be accepted by deterministic 1-turn PDA.
Dr. Nagy is internationally well-known computer scientist (
RG Score above 27) and an associate professor at Department of Mathematics, Faculty of Arts and Sciences, Eastern Mediterranean University, North Cyprus (Turkey).
Presentation: N/A
22. 11. 2017, FIT VUT, Božetěchova 2, Brno
Wednesday, November 22, 2017, 14:00 - 15:00, seminar room
C228:
Dr. Benedek Nagy: On 5' → 3' Watson-Crick finite and pushdown automata
Abstract: In 5'→3' Watson-Crick automata the two reading heads start from the two extremes of the input (the opposite ends of the molecule) and finish the process when the heads meet. With 5'→3' Watson-Crick finite automata the class of linear context-free languages can be accepted, and some of its subclasses by some restricted variants. Extending these automata with a pushdown stack, a new mildly context-sensitive family of languages can be accepted containing all the context-free languages, and the linguistically important three non-context-free languages. Variants of this model will also be shown.
Presentation: N/A
10. 4. 2017, 13:00 - 14:00,
A112, FIT VUT, Božetěchova 2, Brno.
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Anotace: Výslovnost americké angličtiny obsahuje některé zvuky, které Čech imituje chybně. Učitelé, včetně rodilých mluvčích, tyto odchylky zpravidla tolerují a spokojí se s touto nesprávně provedenou imitací, pokud je alespoň trochu srozumitelná. Prezentovaná přednáška naopak na tyto zvuky explicitně upozorní a načrtne, jak je vysloví Američan. Prezentace bude mít neformální charakter.
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2016
5. 12. 2016, 10:00 - 11:00,
G202
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Podrobný program -
zde (přednášky vedeny v angličtině)
2015
14. 12. 2015, 13:00 - 14:00,
A113
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Podrobný program -
zde (přednášky vedeny v angličtině)
15. 6. 2015, 13:00 - 14:30,
G108
2014
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Podrobný program -
zde (přednášky vedeny v angličtině)
9. 12. 2014, 14:00-15:00, room D2, FI MUNI, Botanická 68a, Brno
2013
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Podrobný program -
zde (přednášky vedeny v angličtině)
2012
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Podrobný program -
zde (přednášky vedeny v angličtině)
2011
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2. 11. 2011, 12:00 - 13:00, C228
P. Dömösi (College of Nyíregyháza, Hungary): Something About Cryptography
Abstract: Symmetric and asymetric cryptosystems are considered including Polybius cryptosystem, Caesar code, Richelieu cryptosystem, Enigma, Purple, Navajo code, DES, RSA, Pretty Good Pryvacy. In addition a novel symmetric cryptosystem is shown.
G. Horváth (University of Debrecen, Hungary): The Language of Primitive Words
Abstract: A nonempty word is said to be primitive if it is not a proper power of another word. A number of papers investigated the language of all primitive words over an alphabet with more than one letter, concerning its relation to the Chomsky hierarchy. In [1] the authors conjectured that this language is not context-free. This twenty years old conjecture is still open. In this talk I will present recent results and our ongoing research on this topic.
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21. 7. 2011, 10:00 - 11:00, C228
János Falucskai (College of Nyíregyháza, Hungary): A New Interpretation of the Decipherability
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7. 7. 2011, 10:00 - 11:00, C228
P. Dömösi (College of Nyíregyháza, Hungary): Context-free languages and primitive words
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29. 3. 2011, 11:00 - 13:00, A113
J. Falucskai (College of Nyíregyháza, Hungary): Some Algorithms Concerning Uniquely Decipherable Codes
Abstract: The following problem plays an important role in code theory and its applications: Having a set of codewords we have to decide whether there are two or more sequences of codewords which form the same chain of characters of codewords. The problem can be approached in various ways, so the algorithms concerning uniquely decipherable codes use different devices for testing this property. The algorithm of Sardinas–Patterson is based on sequences of sets, other algorithms solve this problem by using finite automata. We present our algorithm, which is based on FA-s.
G. Horváth (University of Debrecen, Hungary): Pumping lemmas for linear and nonlinear context-free languages
Abstract: Iteration lemmas are created to prove that given languages do not belong to certain language classes. There are several known pumping lemmas for the whole class and some special classes of the context-free languages. In this talk we recall some old and present some new, interesting pumping lemmas for special linear and context-free language classes. Some of them can be used to pump regular languages in two place simultaneously. Other lemma can be used to pump context-free languages in arbitrary many places.
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23. 3. 2011, 10:00, C228
16. 3. 2011, 10:00, C228
9. 3. 2011, 10:00, C228
2. 3. 2011, 10:00, C228
16. 2. 2011, 11:00, C228
2010
24. 11., 1. 12., 8. 12., 15. 12. 2010, 9:00 - 12:00, C228
3. 11. 2010, 12:15, A112
20. 10. 2010, 12:15, A112
28. 4. 2010, 11:00, C228
14. 4. 2010, 11:00, C228
7. 4. 2010, 11:00, C228
31. 3. 2010, 11:00, C228
24. 3. 2010, 11:00, C228
17. 3. 2010, 11:00, C228
10. 3. 2010, 11:00, C228
2009
2.12.2009, 12:00, C228
25.11.2009, 12:00, C228
18.11.2009 - VOLNO
11.11.2009, 12:00, C228
4.11.2009, 12:00, C228
21.10.2009, 12:00, C228
14.10.2009, 12:00, C228
07.10.2009, 12:00, C228
23.09.2009, 12:00, C228
Regulovaný nedeterminismus v zásobníkových automatech (T. Masopust)
Základní informace o hledání literatury ve formálních jazycích (Z. Křivka, cca 10 minut)
20.05.2009, 12:00, C228
Privátní sekce
Historie
Seminář v zimním semestru akademického roku 2011/2012 probíhal nepravidelně ve
středu od
12:00 v místnosti
C228.
Seminář v letním semestru akademického roku 2010/2011 probíhal ve
středu od
10:00 v místnosti
C228.
Seminář v zimním semestru akademického roku 2010/2011 probíhal ve
středu od
12:15 v místnosti
A112.
Seminář v letním semestru akademického roku 2009/2010 probíhal ve
středu od
11:00 v místnosti
C228. Plnohodnotné semináře jsou nově pořádány pod záštitou
ústavních seminářů UIFS.
Zajímavé odkazy
DBLP - databáze publikací z Computer Science
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