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22
Normal Form Algorithms for Extended ContextFree Grammars
 Theoretical Computer Science
, 2000
"... We investigate the complexity of a variety of normalform transformations for extended contextfree grammars, where by extended we mean that the set of righthand sides for each nonterminal in such a grammar is a regular set. The study is motivated by the implementation project GraMa which will p ..."
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Cited by 19 (2 self)
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We investigate the complexity of a variety of normalform transformations for extended contextfree grammars, where by extended we mean that the set of righthand sides for each nonterminal in such a grammar is a regular set. The study is motivated by the implementation project GraMa which will provide a C++ toolkit for the symbolic manipulation of contextfree objects just as Grail does for regular objects. Our results generalize known complexity bounds for contextfree grammars but do so in nontrivial ways. Specifically, we introduce a new representation scheme for extended contextfree grammars (the symbolthreaded expression forest), a new normal form for these grammars (dot normal form) and new regular expression algorithms. 1 Introduction In the 1960's, extended contextfree grammars were introduced, based on BackusNaur form, as a useful abbreviatory notation that made contextfree grammars easier to write. More recently, the Standardized General Markup Language (SGML...
Enumerating regular expressions and their languages
 In International Conference on Implementation and Application of Automata (CIAA
, 2004
"... Abstract. We discuss enumeration of regular expressions and the distinct languages they represent. 1 ..."
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Cited by 14 (2 self)
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Abstract. We discuss enumeration of regular expressions and the distinct languages they represent. 1
Policydriven memory protection for reconfigurable hardware
 In Proceedings of the European Symposium on Research in Computer Security (ESORICS), volume LNCS 4189
, 2006
"... Abstract. While processor based systems often enforce memory protection to prevent the unintended sharing of data between processes, current systems built around reconfigurable hardware typically offer no such protection. Several reconfigurable cores are often integrated onto a single chip where th ..."
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Cited by 12 (6 self)
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Abstract. While processor based systems often enforce memory protection to prevent the unintended sharing of data between processes, current systems built around reconfigurable hardware typically offer no such protection. Several reconfigurable cores are often integrated onto a single chip where they share external resources such as memory. While this enables small form factor and low cost designs, it opens up the opportunity for modules to intercept or even interfere with the operation of one another. We investigate the design and synthesis of a memory protection mechanism capable of enforcing policies expressed as a formal language. Our approach includes a specialized compiler that translates a policy of legal sharing to reconfigurable logic blocks which can be directly transferred to an FPGA. The efficiency of our access language design flow is evaluated in terms of area and cycle time across a variety of security scenarios.
Interactive manipulation of regular objects with FAdo
 In Proceedings of 2005 Innovation and Technology in Computer Science Education (ITiCSE 2005). ACM
, 2005
"... FAdo 1 is an ongoing project which aims the development of an interactive environment for symbolic manipulation of formal languages. In this paper we focus in the description of interactive tools for teaching and assisting research on regular languages, and in particular finite automata and regular ..."
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Cited by 11 (7 self)
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FAdo 1 is an ongoing project which aims the development of an interactive environment for symbolic manipulation of formal languages. In this paper we focus in the description of interactive tools for teaching and assisting research on regular languages, and in particular finite automata and regular expressions. Those tools implement most standard automata operations, conversion between automata and regular expressions, and word recognition. We illustrate their use in training and automatic assessment. Finally we present a graphical environment for editing and interactive visualisation.
Assembling Molecules in Atomix is Hard
, 2001
"... . It is shown that assembling molecules in the Atomix game can be used to simulate nite automata. In particular, an instance of Atomix is constructed that has a solution if and only if the nonemptiness intersection problem for nite automata is solvable. This shows that the game under considerat ..."
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Cited by 10 (1 self)
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. It is shown that assembling molecules in the Atomix game can be used to simulate nite automata. In particular, an instance of Atomix is constructed that has a solution if and only if the nonemptiness intersection problem for nite automata is solvable. This shows that the game under consideration is PSPACEcomplete, improving a recent result of Huner et al. [9]. Thus, there are Atomix games which have superpolynomially long optimal solutions. We also give an easy construction of Atomix game levels whose optimal solutions meet the worst case. 1
FAdo and GUItar: tools for automata manipulation and visualization
 14th CIAA 2009, volume 5642 of LNCS
, 2009
"... Abstract. FAdo is an ongoing project which aims to provide a set of tools for symbolic manipulation of formal languages. To allow highlevel programming with complex data structures, easy prototyping of algorithms, and portability (to use in computer grid systems for example), are its main features. ..."
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Cited by 7 (5 self)
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Abstract. FAdo is an ongoing project which aims to provide a set of tools for symbolic manipulation of formal languages. To allow highlevel programming with complex data structures, easy prototyping of algorithms, and portability (to use in computer grid systems for example), are its main features. Our main motivation is the theoretical and experimental research, but we have also in mind the construction of a pedagogical tool for teaching automata theory and formal languages. For the graphical visualization and interactive manipulation a new interface application, GUItar, is being developed. In this paper, we describe the main components of the FAdo system as well as the basics of the graphical interface and editor, the export/import filters and its generic interface with external systems, such as FAdo. 1
Subset construction complexity for homogeneous automata, position automata and ZPCstructures
 Theoretical Computer Science
, 2001
"... The aim of this paper is to investigate how subset construction performs on specific families of automata. A new upper bound on the number of states of the subsetautomaton is established in the case of homogeneous automata. The complexity of the two basic steps of subset construction, i.e. the comp ..."
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Cited by 7 (2 self)
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The aim of this paper is to investigate how subset construction performs on specific families of automata. A new upper bound on the number of states of the subsetautomaton is established in the case of homogeneous automata. The complexity of the two basic steps of subset construction, i.e. the computation of deterministic transitions and the set equality tests, is examined depending on whether the nondeterministic automaton is an unrestricted one, an homogeneous one, a position one or a ZPCstructure, which is an implicit construction for a position automaton.
State complexity of union and intersection of finite languages
 In Proceedings of DLT’07, Lecture Notes in Computer Science 4588
, 2007
"... Abstract. We investigate the state complexity of union and intersection for finite languages. Note that the problem of obtaining the tight bounds for both operations was open. We compute the upper bounds based on the structural properties of minimal deterministic finitestate automata (DFAs) for fin ..."
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Cited by 5 (3 self)
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Abstract. We investigate the state complexity of union and intersection for finite languages. Note that the problem of obtaining the tight bounds for both operations was open. We compute the upper bounds based on the structural properties of minimal deterministic finitestate automata (DFAs) for finite languages. Then, we show that the upper bounds are tight if we have a variable sized alphabet that can depend on the size of input DFAs. In addition, we prove that the upper bounds are unreachable for any fixed sized alphabet. 1
Extended ContextFree Grammars and Normal Form Algorithms
, 1998
"... We investigate the complexity of a variety of normalform transformations for extended contextfree grammars, where by extended we mean that the set of righthand sides for each nonterminal in such a grammar is a regular set. The study is motivated by the implementation project GraMa which will prov ..."
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Cited by 4 (2 self)
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We investigate the complexity of a variety of normalform transformations for extended contextfree grammars, where by extended we mean that the set of righthand sides for each nonterminal in such a grammar is a regular set. The study is motivated by the implementation project GraMa which will provide a C++ toolkit for the symbolic manipulation of contextfree objects just as Grail does for regular objects. Our results generalize known bounds for contextfree grammars but do so in nontrivial ways. Specifically, we introduce a new representation scheme for extended contextfree grammars (the symbolthreaded expression forest), a new normal form for these grammars (dot normal form) and new regular expression algorithms. 1 Introduction in the 1960's, extended contextfree grammars were introduced, using BackusNaur form, as a useful abbreviatory notation that made contextfree grammars easier to write. More recently, the Standardized General Markup Language (SGML) [13] used a similar ab...
Enforcing Memory Policy Specifications in Reconfigurable Hardware
"... While generalpurpose processor based systems are built to enforce memory protection to prevent the unintended sharing of data between processes, current systems built around reconfigurable hardware typically offer no such protection. Several reconfigurable cores are often integrated onto a single c ..."
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Cited by 1 (0 self)
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While generalpurpose processor based systems are built to enforce memory protection to prevent the unintended sharing of data between processes, current systems built around reconfigurable hardware typically offer no such protection. Several reconfigurable cores are often integrated onto a single chip where they share external resources such as memory. While this enables small form factor and low cost designs, it opens up the opportunity for modules to intercept or even interfere with the operation of one another. We investigate the design and synthesis of a FPGA memory protection mechanism capable of enforcing access control policies and a methodology for translating formal policy descriptions into FPGA enforcement mechanisms. The efficiency of our access language design flow is evaluated in terms of area and cycle time across a variety of security scenarios. We also describe a technique for ensuring that the internal state of the reference monitor cannot be used as a covert storage channel.