On the Size Complexity of Non-Returning Context-Free PC Grammar Systems

Improving the previously known best bound, we show that any recursively enumerable language can be generated with a non-returning parallel communicating (PC) grammar system having six context-free components. We also present a non-returning universal PC grammar system generating unary languages, that is, a system where not only the number of components, but also the number of productions and the number of nonterminals are limited by certain constants, and these size parameters do not depend on the generated language

Contributions of formal language theory to the study of dialogues

For more than 30 years, the problem of providing a formal framework for modeling dialogues has been a topic of great interest for the scientific areas of Linguistics, Philosophy, Cognitive Science, Formal Languages, Software Engineering and Artificial Intelligence. In the beginning the goal was to develop a "conversational computer", an automated system that could engage in a conversation in the same way as humans do. After studies showed the difficulties of achieving this goal Formal Language Theory and Artificial Intelligence have contributed to Dialogue Theory with the study and simulation of machine to machine and human to machine dialogues inspired by Linguistic studies of human interactions. The aim of our thesis is to propose a formal approach for the study of dialogues. Our work is an interdisciplinary one that connects theories and results in Dialogue Theory mainly from Formal Language Theory, but also from another areas like Artificial Intelligence, Linguistics and Multiprogramming. We contribute to Dialogue Theory by introducing a hierarchy of formal frameworks for the definition of protocols for dialogue interaction. Each framework defines a transition system in which dialogue protocols might be uniformly expressed and compared. The frameworks we propose are based on finite state transition systems and Grammar systems from Formal Language Theory and a multi-agent language for the specification of dialogue protocols from Artificial Intelligence. Grammar System Theory is a subfield of Formal Language Theory that studies how several (a finite number) of language defining devices (language processors or grammars) jointly develop a common symbolic environment (a string or a finite set of strings) by the application of language operations (for instance rewriting rules). For the frameworks we propose we study some of their formal properties, we compare their expressiveness, we investigate their practical application in Dialogue Theory and we analyze their connection with theories of human-like conversation from Linguistics. In addition we contribute to Grammar System Theory by proposing a new approach for the verification and derivation of Grammar systems. We analyze possible advantages of interpreting grammars as multiprograms that are susceptible of verification and derivation using the Owicki-Gries logic, a Hoare-based logic from the Multiprogramming field

Regulated Automata Systems

Tato práce zavádí a studuje dva nové typy automatů, spolupracující distribuované systémy zásobníkových automatů (CDPDAS) a paralelní komunikující systémy zásobníkových automatů (PCPDAS), které jsou inspirovany spolupracujícími distribuovanými gramatickými systémy (CDGS), paralelními komunikujícími gramatickými systémy (PCGS) a jejich modifikacemi.  CDGS používají bezkontextová pravidla a přesto zvyšují sílu nad úroveň bezkontextových gramatik, leč zavedení distribuované spolupráce k zásobníkovým automatům sílu nezvyšuje.  Dokázána je schopnost simulovat distribuovanou spolupráci pouze za použití stavu.  Práce z tohoto výsledku dále vychází a zavádí variantu CDPDAS lišící se od všech variant CDGS, která zvyšuje sílu na roveň Turingových strojů (TM).  PCGS mají sílu podobnou s CDGS, ale jimi inspirované PCPDAS jsou ekvivalení s TM, což je dokázáno umožněním přístupu k druhému zásobníku pomocí neintuitivního komunikačního protokolu.This thesis defines and studies two new types of automata, cooperating distributed pushdown automata systems (CDPDAS) and parallel communicating pushdown automata systems (PCPDAS).  CDPDAS and PCPDAS adapt the main concept of cooperating distributed grammar systems (CDGS) and parallel communicating automata systems (PCPDAS), respectively.  CDPDAS are proven to have the same power as PDA and this thesis further explores the reason why CDPDAS do not increase power while CDGS do and introduces an automata system inspired by CDPDAS that does increase the power.  PCGS have similar power as CDGS, but PCPDAS are equvalent with TM, which is proven by creating a communication protocol to access a second stack.

libcppa - Designing an Actor Semantic for C++11

Parallel hardware makes concurrency mandatory for efficient program execution. However, writing concurrent software is both challenging and error-prone. C++11 provides standard facilities for multiprogramming, such as atomic operations with acquire/release semantics and RAII mutex locking, but these primitives remain too low-level. Using them both correctly and efficiently still requires expert knowledge and hand-crafting. The actor model replaces implicit communication by sharing with an explicit message passing mechanism. It applies to concurrency as well as distribution, and a lightweight actor model implementation that schedules all actors in a properly pre-dimensioned thread pool can outperform equivalent thread-based applications. However, the actor model did not enter the domain of native programming languages yet besides vendor-specific island solutions. With the open source library libcppa, we want to combine the ability to build reliable and distributed systems provided by the actor model with the performance and resource-efficiency of C++11.Comment: 10 page

Submicron Systems Architecture: Semiannual Technical Report

No abstract available

Generation of Distributed Programming Environments

This technical report consists of three related papers in the area of distributed programming environments. Incremental Attribute Evaluation in Distributed Language-Based Environments presents algorithms that extend existing technology for the generation of single-user language-based editors from attribute grammars to the cases of multiple-user concurrent and distributed environments. Multi-User Distributed Language-Based Environment, an extended abstract, provides additional information on how to apply the algorithms. Reliability in Distributed Programming Environments presents additional algorithms that extend our results to unreliable networks