Finite Equational Bases in Process Algebra: Results and Open Questions

Van Glabbeek (1990) presented the linear time-branching time spectrum of behavioral equivalences for finitely branching, concrete, sequential processes. He studied these semantics in the setting of the basic process algebra BCCSP, and tried to give finite complete and omega-complete axiomatizations for them. (An axiomatization E is omega-complete when an equation can be derived from E if, and only if, all its closed instantiations can be derived from E.) Obtaining such axiomatizations in concurrency theory often turns out to be difficult, even in the setting of simple languages like BCCSP. This has raised a host of open questions that have been the subject of intensive research in recent years. Most of these questions have been settled over BCCSP, either positively by giving a finite complete or omega-complete axiomatization, or negatively by proving that such an axiomatization does not exist. Still some open questions remain. This paper reports on these results, and on the state-of-the-art on axiomatizations for richer process algebras, containing constructs like sequential and parallel composition.

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Ready To Preorder: Get Your BCCSP Axiomatization for Free!

BRICS Report Series ◽

10.7146/brics.v14i3.21926 ◽

2007 ◽

Vol 14 (3) ◽

Cited By ~ 2

Author(s):

Luca Aceto ◽

Willem Jan Fokkink ◽

Anna Ingólfsdóttir

Keyword(s):

Process Algebra ◽

Linear Time ◽

Equational Theory ◽

Time Spectrum ◽

Basic Process ◽

Branching Time ◽

Discriminating Power

This paper contributes to the study of the equational theory of the semantics in van Glabbeek's linear time - branching time spectrum over the language BCCSP, a basic process algebra for the description of finite synchronization trees. It offers an algorithm for producing a complete (respectively, ground-complete) equational axiomatization of a behavioral congruence lying between ready simulation equivalence and partial traces equivalence from a complete (respectively, ground-complete) inequational axiomatization of its underlying precongruence--that is, of the precongruence whose kernel is the equivalence. The algorithm preserves finiteness of the axiomatization when the set of actions is finite. It follows that each equivalence in the spectrum whose discriminating power lies in between that of ready simulation and partial traces equivalence is finitely axiomatizable over the language BCCSP if so is its defining preorder.

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NONLINEAR WAVE PROPAGATION IN DISORDERED MEDIA

International Journal of Modern Physics B ◽

10.1142/s0217979291001115 ◽

1991 ◽

Vol 05 (18) ◽

pp. 2825-2882 ◽

Cited By ~ 33

Author(s):

ANGEL SÁNCHEZ ◽

LUIS VÁZQUEZ

Keyword(s):

Wave Propagation ◽

Nonlinear Wave ◽

State Of The Art ◽

Disordered Media ◽

Nonlinear Wave Propagation ◽

General Introduction ◽

Current Trends ◽

Open Questions ◽

Klein Gordon ◽

The Subject

We briefly review the state-of-the-art of research on nonlinear wave propagation in disordered media. The paper is intended to provide the non-specialist reader with a flavor of this active field of physics. Firstly, a general introduction to the subject is made. We describe the basic models and the ways to study disorder in connection with them. Secondly, analytical and numerical techniques suitable for this purpose are outlined. We summarize their features and comment on their respective advantages, drawbacks and applicability conditions. Thirdly, the Nonlinear Klein-Gordon and Schrödinger equations are chosen as specific examples. We collect a number of results that are representative of the phenomena arising from the competition between nonlinearity and disorder. The review is concluded with some remarks on open questions, main current trends and possible further developments.

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Highly Undecidable Questions for Process Algebras

BRICS Report Series ◽

10.7146/brics.v11i8.21833 ◽

2004 ◽

Vol 11 (8) ◽

Author(s):

Petr Jancar ◽

Jirí Srba

Keyword(s):

Petri Nets ◽

Process Algebra ◽

Basic Process ◽

Process Algebras ◽

Parallel Processes ◽

Pushdown Automata ◽

Trace Equivalence

We show Sigma^1_1-completeness of weak bisimilarity for PA (process algebra), and of weak simulation preorder/equivalence for PDA (pushdown automata), PA and PN (Petri nets). We also show Pi^1_1-hardness of weak omega-trace equivalence for the (sub)classes BPA (basic process algebra) and BPP (basic parallel processes).

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A Menagerie of Non-Finitely Based Process Semantics over BPA*: From Ready Simulation Semantics to Completed Traces

BRICS Report Series ◽

10.7146/brics.v3i23.20003 ◽

1996 ◽

Vol 3 (23) ◽

Cited By ~ 1

Author(s):

Luca Aceto ◽

Willem Jan Fokkink ◽

Anna Ingólfsdóttir

Keyword(s):

Process Algebra ◽

Linear Time ◽

Subject Classification ◽

Regular Expressions ◽

Basic Process ◽

Branching Time ◽

Finitely Based ◽

Trace Semantics ◽

Bisimulation Equivalence ◽

Trace Equivalence

Fokkink and Zantema ((1994) Computer Journal 37:259-267) have shown that bisimulation equivalence has a finite equational axiomatization over the language of Basic Process Algebra with the binary Kleene star operation (BPA*). In light of this positive result on the mathematical tractability of bisimulation equivalence over BPA*, a natural question to ask is whether any other (pre)congruence relation in van Glabbeek's linear time/branching time spectrum is finitely (in)equationally axiomatizable over it. In this paper, we prove that, unlike bisimulation equivalence, none of the preorders and equivalences in van Glabbeek's linear time/branching time spectrum, whose discriminating power lies in between that of ready simulation and that of completed traces, has a finite equational axiomatization. This we achieve by exhibiting a family of (in)equivalences that holds in ready simulation semantics, the finest semantics that we consider, whose instances cannot all be proven by means of any finite set of (in)equations that is sound in completed trace semantics, which is the coarsest semantics that is appropriate for the language BPA*. To this end, for every finite collection of (in)equations that are sound in completed trace semantics, we build a model in which some of the (in)equivalences of the family under consideration fail. The construction of the model mimics the one used by Conway ((1971) Regular Algebra and Finite Machines, page 105) in his proof of a result, originally due to Redko, to the effect that infinitely many equations are needed to axiomatize equality of regular expressions.Our non-finite axiomatizability results apply to the language BPA* over an arbitrary non-empty set of actions. In particular, we show that completed trace equivalence is not finitely based over BPA* even when the set of actions is a singleton. Our proof of this result may be easily adapted to the standard language of regular expressions to yield a solution to an open problem posed by Salomaa ((1969) Theory of Automata, page 143). Another semantics that is usually considered in process theory is trace semantics. Trace semantics is, in general, not preserved by sequential composition, and is therefore inappropriate for the language BPA*. We show that, if the set of actions is a singleton, trace equivalence and preorder are preserved by all the operators in the signature of BPA, and coincide with simulation equivalence and preorder, respectively. In that case, unlike all the other semantics considered in this paper, trace semantics have nite, complete equational axiomatizations over closed terms. AMS Subject Classification (1991): 08A70, 03C05, 68Q10, 68Q40, 68Q45, 68Q55, 68Q68, 68Q70. CR Subject Classification (1991): D.3.1, F.1.1, F.1.2, F.3.2, F.3.4, F.4.1. Keywords and Phrases: Concurrency, process algebra, Basic Process Algebra (BPA*), Kleene star, bisimulation, ready simulation, simulation, completed trace semantics, ready trace semantics, failure trace semantics, readiness semantics, failures semantics, trace semantics, equational logic, complete axiomatizations.

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The Linear Time - Branching Time Spectrum I.**This is an extension of [20]. The research reported in this paper has been initiated at CWI in Amsterdam, continued at the Technical University of Munich, and finalized at Stanford University. It has been supported by Sonderforschungsbereich 342 of the TU München and by ONR under grant number N00014-92-J-1974. Part of it was carried out in the preparation of a course Comparative Concurrency Semantics, given at the University of Amsterdam, Spring 1988. A coloured version of this paper is available at http://boole.stanford.edu/pub/spectruml.ps.gz. The Semantics of Concrete, Sequential Processes

Handbook of Process Algebra ◽

10.1016/b978-044482830-9/50019-9 ◽

2001 ◽

pp. 3-99 ◽

Cited By ~ 173

Author(s):

R.J. van Glabbeek

Keyword(s):

Linear Time ◽

Time Spectrum ◽

Stanford University ◽

Branching Time ◽

University Of Munich ◽

Sequential Processes ◽

Technical University ◽

The University

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Strong Bisimilarity of Simple Process Algebras: Complexity Lower Bounds

BRICS Report Series ◽

10.7146/brics.v9i16.21734 ◽

2002 ◽

Vol 9 (16) ◽

Cited By ~ 1

Author(s):

Jirí Srba

Keyword(s):

General Framework ◽

Process Algebra ◽

Basic Process ◽

Process Algebras ◽

Strong Regularity ◽

New Techniques ◽

Simple Process ◽

Rewrite Systems ◽

Parallel Processes ◽

Complexity Lower Bounds

In this paper we study bisimilarity problems for simple process algebras. In particular, we show PSPACE-hardness of the following problems:<ol><li>strong bisimilarity of Basic Parallel Processes (BPP),</li><li>strong bisimilarity of Basic Process Algebra (BPA),</li><li>strong regularity of BPP, and</li><li>strong regularity of BPA.</li></ol>We also demonstrate NL-hardness of strong regularity problems for the normed subclasses of BPP and BPA. Bisimilarity problems for simple process algebras are introduced in a general framework of process rewrite systems, and a uniform description of the new techniques used for the hardness proofs is provided.

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PLANEJAMENTO FAMILIAR COMO ASSUNTO DE MULHER!? PERFIL DE GÊNERO NA PRODUÇÃO CIENTÍFICA NO BRASIL

Revista Interdisciplinar de Estudos em Saúde ◽

10.33362/ries.v8i1.1511 ◽

2019 ◽

Vol 8 (1) ◽

pp. 221-235 ◽

Cited By ~ 1

Author(s):

Daniella De Paula Chiesa ◽

Mário Antônio Sanches ◽

Daiane Priscila Simão-Silva

Keyword(s):

Family Planning ◽

Scientific Literature ◽

State Of The Art ◽

Health Sciences ◽

Scientific Production ◽

The State ◽

Review Of The Literature ◽

The Subject

O estudo do Planejamento familiar, no contexto da bioética, abre-se para diversas perspectivas, entre elas a valorização dos seus diferentes atores. Situado neste contexto o artigo tem como objetivo identificar o perfil de gênero na produção científica sobre Planejamento Familiar no Brasil, entre 2000 e 2014, assim como a área de formação e especialização dos autores. Foram utilizadas metodologias que permitiram mapear o estado da arte do tema estudado, a partir de uma revisão da literatura. O resultado da pesquisa identifica que a produção científica sobre Planejamento Familiar no Brasil se compõe de perfil destacadamente feminino (71,76%). Dos 73 artigos analisados, 42 (57,53%) o foco do tema está direcionado à mulher assim como evidencia-se a área de ciências da saúde com maior concentração das publicações do tema. Este aspecto da pesquisa abre para uma realidade complexa onde se buscam criticamente as razões para a pesquisa em Planejamento Familiar ter ênfase na mulher e ser um tema de relevância nas ciências da saúde.Palavras-chave: Produção científica, Planejamento Familiar, Gênero. ABSTRACT: The study of Family Planning, in the context of bioethics, opens to diverse perspectives, among them the appreciation of their different agents. Situated in this context the article aims to identify the profile of gender in scientific literature on Family Planning in Brazil, between 2000 and 2014, as well as the area of training and specialization of the authors. Methodologies were used which allowed to map the State of the art of the subject studied, from a review of the literature. The results found identify that the scientific production on Family Planning in Brazil is formed with a outstandingly female profile (71,76%). Of the 73 articles examined, 42 (57.53%) the focus of the topic is directed to women as well as showing the health sciences area with highest concentration of publications. This aspect of the research opens to a complex reality where we seek critically the reasons for Research in Family Planning have emphasis on woman and be a topic of relevance in health sciences.Keywords: Scientific Production, Family Planning, Gender.

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A Systematic Literature Review of the EFQM Excellence Model from 1991 to 2019

International Journal of Applied Research in Management and Economics ◽

10.33422/ijarme.v2i2.211 ◽

1970 ◽

Vol 2 (2) ◽

pp. 11-15

Author(s):

Muhammad Yousaf ◽

Petr Bris

Keyword(s):

Quality Management ◽

Data Collection ◽

Literature Review ◽

Systematic Literature Review ◽

Quantitative Research ◽

Web Of Science ◽

State Of The Art ◽

Future Research ◽

European Foundation ◽

The Subject

A systematic literature review (SLR) from 1991 to 2019 is carried out about EFQM (European Foundation for Quality Management) excellence model in this paper. The aim of the paper is to present state of the art in quantitative research on the EFQM excellence model that will guide future research lines in this field. The articles were searched with the help of six strings and these six strings were executed in three popular databases i.e. Scopus, Web of Science, and Science Direct. Around 584 peer-reviewed articles examined, which are directly linked with the subject of quantitative research on the EFQM excellence model. About 108 papers were chosen finally, then the purpose, data collection, conclusion, contributions, and type of quantitative of the selected papers are discussed and analyzed briefly in this study. Thus, this study identifies the focus areas of the researchers and knowledge gaps in empirical quantitative literature on the EFQM excellence model. This article also presents the lines of future research.

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Revisiting the High-Pressure Properties of the Metal-Organic Frameworks ZIF-8 and ZIF-67

10.26434/chemrxiv.13146278.v1 ◽

2020 ◽

Author(s):

Pia Vervoorts ◽

Stefan Burger ◽

Karina Hemmer ◽

Gregor Kieslich

Keyword(s):

High Pressure ◽

State Of The Art ◽

Energy Landscape ◽

Structural Flexibility ◽

Zeolitic Imidazolate Frameworks ◽

Stimuli Responsive ◽

X Ray Diffraction ◽

X Ray ◽

Open Questions ◽

Metal Organic

The zeolitic imidazolate frameworks ZIF-8 and ZIF-67 harbour a series of fascinating stimuli responsive properties. Looking at their responsitivity to hydrostatic pressure as stimulus, open questions exist regarding the isotropic compression with non-penetrating pressure transmitting media. By applying a state-of-the-art high-pressure powder X-ray diffraction setup, we revisit the high-pressure behaviour of ZIF-8 and ZIF-67 up to p = 0.4 GPa in small pressure increments. We observe a drastic, reversible change of high-pressure powder X-ray diffraction data at p = 0.3 GPa, discovering large volume structural flexibility in ZIF-8 and ZIF-67. Our results imply a shallow underlying energy landscape in ZIF-8 and ZIF-67, an observation that might point at rich polymorphism of ZIF-8 and ZIF-67, similar to ZIF-4(Zn).

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