Petr Zemek

• Ph.D.
• Researcher at Brno University of Technology

By regulated grammars, this book refers to any context-free grammars extended by additional mathematical mechanisms that prescribe the use of rules during the generation of their languages. The book pays a special attention to these six crucially important regulated grammars---regular-controlled grammars, matrix grammars, programmed grammars, rando...

This book offers key theoretical topics and terminology concerning regulated grammars and automata. They are the most important language-defining devices that work under controls represented by additional mathematical mechanisms. Key topics include formal language theory, grammatical regulation, grammar systems, erasing rules, parallelism, word mon...

The present paper proposes a new investigation area in automata theory — jumping finite automata. These automata work like classical finite automata except that they read input words discontinuously — that is, after reading a symbol, they can jump over some symbols within the words and continue their computation from there. The paper establishes se...

The notion of a one-sided random context grammar is defined as a context-free-based regulated grammar, in which a set of permitting symbols and a set of forbidding symbols are attached to every rule, and its set of rules is divided into the set of left random context rules and the set of right random context rules. A left random context rule can re...

This paper establishes two new normal forms for phrase-structure grammars in which both context-free rules and non-context-free rules are in prescribed forms. In addition, a limit is placed on the number of context-free rules. More specifically, the first form has $2 + n$ context-free rules, where $n$ is the number of terminals. Concerning non-cont...

In the presented paper we discuss pure versions of pushdown automata that have no extra non-input symbols. More specifically, we study pure multi-pushdown automata, which have several pushdown lists. We restrict these automata by the total orders defined over their pushdowns or alphabets and determine the accepting power of the automata restricted...

Recall that the notion of a one-sided random context grammar is based upon a finite set of context-free rules, each of which may be extended by finitely many permitting and forbidding nonterminal symbols. The set of all these rules is divided into two sets---the set of left random context rules and the set of right random context rules. When applyi...

In this paper, we address several open problems concerning pure grammar systems (pGSs) and their controlled versions. More specifically, we prove the following four results. (I) Regular-controlled pGSs having a single component define the family of regular languages. (II) pGSs having two components controlled by infinite regular languages define th...

This paper discusses finite automata regulated by control languages over their states and transition rules. It proves that under both regulations, regular-controlled finite automata and context-free-controlled finite automata characterize the family of regular languages and the family of context-free languages, respectively. It also establishes con...

This paper deals with regulated grammars. Specifically, it studies one-sided random context grammars. It demonstrates that any recursively enumerable language can be generated by these grammars with no more than two right random context rules.

Machine-code decompilation, belonging to the area of reverse engineering, has found its applications in many real-world areas. Analysis of malicious software, search for vulnerabilities, and source-code recovery are some of the most important uses. As there exists a diversity of different platforms on which software can be run, an existence of a ge...

Decompilation (i.e. reverse compilation) represents one of the most toughest and challenging tasks in reverse engineering. Even more difficult task is the decompilation of malware because it typically does not follow standard application binary interface conventions, has stripped symbols, is obfuscated, and can contain polymorphic code. Moreover, i...

Machine-code decompilation, belonging to the area of reverse engineering, has found its applications in many real-world areas. Analysis of malicious software, search for vulnerabilities, and source-code recovery are some of the most important uses. As there exists a diversity of different platforms on which software can be run, an existence of a ge...

Consider ET0L grammars. Modify them such that a set of permitting symbols and a set of forbidding symbols are attached to each of their rules, just like in random context grammars. A rule like this can rewrite a symbol if each of its permitting symbols occurs to the left of the symbol to be rewritten in the current sentential form while each of its...

In this paper, we give an overview of the established results concerning one-sided random context grammars, and point out open problems. Additionally, we propose several areas suggested as topics of future investigation related to the study of one-sided random context grammars.

The present paper explains how to transform any regular-controlled (context-free) grammar with appearance checking G to a propagating regular-controlled (context-free) grammar with appearance checking G' whose language L(G') has sentences of the form wz, where w is in L(G) and z is a parse of w in G'. Consequently, for every recursively enumerable...

In generalized one-sided forbidding grammars (GOFGs), each context-free rule has associated a finite set of forbidding strings, and the set of rules is divided into the sets of left and right forbidding rules. A left forbidding rule can rewrite a nonterminal if each of its forbidding strings is absent to the left of the rewritten symbol. A right fo...

This paper discusses grammar systems that have only terminals, work in the leftmost way, and generate their languages under the regulation by control languages over rule labels. It establishes three results concerning their generative power. First, without any control languages, these systems are not even able to generate all context-free languages...

Detection and recovery of high-level control structures, such as functions and their arguments, plays an important role in decompilation. It has a direct impact on the quality of the generated code because it is needed for generating functionally equivalent and highly readable code. In this paper, we present an innovative, platform-independent meth...

Introduction. Decompilation is used for translation of executable files into a high-level language (HLL) representation. It is an important mechanism for information forensics and malware analysis. Retargetable decompilation represents a very difficult task because it must handle all the specific features of the target platform. Nevertheless, a ret...

As its name suggests, a stateless pushdown automaton has no states. As a result, each of its computational steps depends only on the currently scanned symbol and the current pushdown-store top. In this paper, we consider stateless pushdown automata whose size of their pushdown alphabet is limited by a positive integer. More specifically, we establi...

In this paper, we study the generative power of one-sided random context grammars working in a leftmost way. More specifically, by analogy with the three well-known types of leftmost derivations in regulated grammars, we introduce three types of leftmost derivations to one-sided random context grammars and prove the following three results. (I) One...

Many core parts of software applications have been written several decades ago, and they are still essential in several existing projects. However, maintaining these parts is difficult and expensive. The source language itself may be either ancient and ineffective, or its toolchain does not support new platforms and features. Source code migration...

The present paper discusses normal forms of one-sided random context grammars. More specifically, it (1) gives an overview of previously established normal forms and (2) establishes three new normal forms. All normal forms are established in terms of one-sided random context grammars with and without erasing rules. A discussion of an open problem c...

In one-sided forbidding grammars, the set of rules is divided into the set of left forbidding rules and the set of right forbidding rules. A left forbidding rule can rewrite a non-terminal if each of its forbidding symbols is absent to the left of the rewritten symbol in the current sentential form, while a right forbidding rule is applied analogic...

In the present paper, we study the nonterminal complexity of one-sided random context grammars. More specifically, we prove that every recursively enumerable language can be generated by a one-sided random context grammar with no more than ten nonterminals. An analogical result holds for thirteen nonterminals in terms of these grammars with the set...

Accurate program decompilation is one of the most difficult tasks of reverse engineering. Currently, there exist several single-purpose decompilers targeted on a particular platform (e.g. Intel x86 architecture and Microsoft Windows OS) and on a particular language. These tools are always hand-written by the author from scratch. This paper presents...

Reverse program compilation (i.e. decompilation) is a process heavily exploited in reverse engineering. The task of decompilation is to transform a platform-specific executable into a high-level language representation, which is usually the C language. Such a process can be used for source code reconstruction, compiler testing, malware analysis, et...

Together with the massive expansion of smartphones, tablets, and other smart devices, we can notice a growing number of malware threats targeting these platforms. Software security companies are not prepared for such diversity of target platforms and there are only few techniques for platform-independent malware analysis. This is a major security i...

The present paper introduces a new variant of a scattered context grammar, called an LL leftmost k‐linear scattered context grammar. It is an ordinary scattered context grammar without erasing rules, where (1) every scattered context rule is composed of k‐linear rules, (2) if we take the first components of every rule, the resulting context‐free gr...

In the present paper, we discuss programmed grammars. More specifically, we discuss their nondeterministic behaviour and its reduction. We prove that for every programmed grammar, there exists an equivalent programmed grammar where only a single rule has more than one successor. Furthermore, we establish an infinite hierarchy of language families r...

Together with the massive expansion of smartphones, tablets, and other smart devices, we can notice a growing number of malware threats targeting these platforms. Software security companies are not prepared for such diversity of target platforms and there are only few techniques for platform-independent malware analysis. This is a major security i...

This paper establishes a workspace theorem in terms of regular-controlled (context-free) grammars. It proves that, if, for a regular-controlled grammar H, there is a positive integer k such that H generates every sentence y in L(H) by a derivation in which every sentential form x contains at most (k-1)|x|/k occurrences of nonterminals that are eras...

The present paper studies the nonterminal complexity of left random context E0L grammars. More specifically, it proves that every recursively enumerable language can be generated by a left random context E0L grammar with nine nonterminals. In the conclusion, some open problems related to the achieved result are stated.

A regular-controlled context-free grammar erases its nonterminals in a k-limited way, where k >= 0, if in every sentential form x of any successful derivation x contains at most k|x|/(k+1) nonterminals from which it does derive the empty string, where |x| is the length of x. This paper demonstrates that any regular-controlled context-free grammar t...

This paper establishes an equivalence between n-limited state grammars and n-limited pro-grammed grammars. This equivalence results into an infinite hierarchy of language families resulting from n-limited programmed grammars, which can be considered in syntactical analysis, when writing a parser based on programmed grammars.