Cause-effect structures are objects of a formal system devised for modeling, testing and verifying properties of tasks, where parallel execution of actions is the most characteristic feature. This is an algebraic system called a quasi-semiring. In this paper elementary cause-effect structures, a system behaviourally equivalent to 1-safe Petri nets, are extended by the following features: weighted edges, multi-valued nodes having capacities (counterpart of place/transition Petri nets), inhibitors and a model of time. The extensions are accomplished by modifying the notion of state and semantics, but leaving unchanged structure of the quasi-semiring expressions.

A new protocol using vectors of global timestamps for mutual exclusion in systems with Distributed Shared Memory (DSM) is described and some of its properties are proved.

Two observations in the matter of pictorial as well as formal presentation of some consistency in distributed shared memory are made. The first concerns geometric transformation of line segments and points picturing read/write operations, the second - converting partial order of the operations into linear order of their initiations and terminations. This allows to reduce serialization of the read/write operations as a whole to permutations of their beginnings and ends. Some draft proposals are introduced.

This is the seventeenth special issue of Fundamenta Informaticae based on the CONCURRENCY SPECIFICATION AND PROGRAMMING (CS&P) workshop, in succession to the sixteenth special issue published in 2014.The CS&P workshops, being held every even year in Germany and every odd year in Poland, take place on the basis of an exchange programme between University of Warsaw and Humboldt University in Berlin.Initiated by computer science and mathematical logic interest groups affiliated to Warsaw and Humboldt Universities in the mid-seventies of the XX century, the workshops were suspended for some years in the eighties and resumed in 1992 in the extended form of participation: they evolved from bilateral meetings to the meetings hosting researchers also from a number of countries other than Germany and Poland.The scope of subjects has been broadened too: from linguistic and logical issues initially to diverse research areas such as, for instance, the aforesaid ones.This part contains selected and extended versions of 11 out of 32 articles presented at the meeting that took place in Chemnitz from September 29 to October 1, 2014.As it was the case of all the previous special issues of Fundamenta Informaticae based on CS&P, the articles were selected on the basis of a review process admitted by international scientific periodicals.A complete collection of the contributions has been edited by Louchka Popova-Zeugmann and Holger Schlingloff of Humboldt University and Matthias Werner of Technical University, Chemnitz and published before the workshop as Proceedings.This is, thus, a continuation of the tradition of the former CS&Ps, whose participants had been supplied with proceedings in the form of technical reports during the meetings.The articles contained in this special issue, cover the following topics: Mathematical models of concurrency, Specification languages, Theory of programming, Parallel algorithms, Model checking and testing, Multi-agent systems, Rough sets, Object-oriented approaches, Knowledge management, Knowledge discovery and data mining, Soft computing, Information technology and management, as well as Applications.In order to provide the readers with a better insight into this special issue, we enclose below brief overviews of the accepted papers.The first two articles 'A Classifier Based on a Decision Tree with Verifying Cuts' and 'Classifiers for Behavioral Patterns Identification Induced from Huge Temporal Data', written by members of the Jan G. Bazan's group, are devoted to constructing hierarchical classifiers.The first one considers building decision trees based on additional cuts, while the second one deals with temporal data.

This special issue of Fundamenta Informaticae is dedicated to papers selected from the 24th International Workshop on CONCURRENCY, SPECIFICATION, AND PROGRAMMING (CS&P 2015), which was held in September 28 -30, 2015 in Rzeszów, Poland.After the event, some authors of the papers presented at the workshop were invited to submit a revised and extended version of their papers, which underwent another reviewing process to guarantee that the revised papers meet the standards of FUNDAMENTA INFORMATICAE.Eventually, twelve papers have been selected for publication in this special issue, which gives a representative account of current issues and topics related to Concurrency, Specification, and Programming.A complete collection of the contributions to CS&P 2015 has been edited by scientists of University of Rzeszów and published before the workshop as Proceedings.The article 'Comparison of Heuristics for Optimization of Association Rules' by Fawaz Alsolami, Talha Amin, Igor Chikalov, Mikhail Moshkov, and Beata Zielosko, includes several heuristics for construction of association rules.The presented experimental results show that the difference concerning the length or coverage obtained by the best heuristic and optimal ones (constructed using dynamic programming algorithms) are small.In the paper 'Specialized Predictor for Reaction Systems with Context Properties' Roberto Barbuti, Roberta Gori, Francesca Levi, and Paolo Milazzo consider reaction systems.They revise the notion of formula based predictor by defining a specialized version that assumes the environment to provide molecules according to what expressed by a temporal logic formula.As an application, specialized formula based predictors are used to give theoretical grounds to a model of gene regulation.

This special volume of Fundamenta Informaticae is dedicated to the memory of Professor Manfred Kudlek, who died on 18th of June 2012.It contains a reminiscent note about Manfred and 13 research papers, selected out of those invited to the volume following a referee process.The papers present original contributions to some areas that theoretical informatics encompasses.They belong to the following topics: (1) theory of concurrency, (2) distributed computer systems, (3) machine learning, (4) timed automata, (5) theory of formal languages, (6) rough set theory, (7) classification problems, (8) mereological methods in computer science, (9) multiagent systems, (10) computer science approaches to economy, (11) formal models of biochemical reaction networks.Obviously, some contributions may be classified as falling into more than one area.The volume contains also a joint paper by Manfred Kudlek and Nils Erik Flick prepared to be published just before the unfortunate June 2012.

Petri net structures are used as communication model of network systems where message transfer channels are represented by the nets' edges, communicating agents - by nets' places and actions of communication - by nets' transitions, which here are called transmissions. The role of (structured) tokens play send/receive statements, that arrive at random, which makes the distribution of edges change dynamically. In this sense a net is self-modyfying: although the set of agents-places is fixed, the channels and communicating actions vary in the course of the net activity. Problems of deadlock and fairness is investigated.

A network system is given as a set of Petri net-like structures called agents. Each agent has a singled out place interpreted as a communication port with ingoing edges labelled with send(p1 , ..., pn ) and receive(q1 , ..., qm ) commands, where pi ,

This is the first part of the sixteenth special issue of Fundamenta Informaticae based on the CON-CURRENCY SPECIFICATION AND PROGRAMMING (CS&P) workshop, in succession to the fifteenth special issue published in 2013.This part contains selected and extended versions of 15 out of 42 papers presented at the meeting that took place in Warsaw from 25 to 27 September 2013.As it was the case of all the previous special issues of Fundamenta Informaticae based on CS&P, the papers were selected on the basis of a review process admitted by international scientific periodicals.A complete collection of the contributions has been edited by scientists of University of Warsaw and published before the workshop as Proceedings.This is, thus, a continuation of the tradition of the former CS&Ps, whose participants had been supplied with proceedings in the form of technical reports during the meetings.The papers contained in both parts of the special issue cover the following topics: mathematical models of concurrent systems, parallel algorithms, model checking, multiagent systems, rough sets, workflow systems, mereological approaches, knowledge management, knowledge discovery and data mining, neural networks, machine learning, robotics, genetic algorithms, soft computing and some applications.The CS&P workshops, being held every even year in Germany and every odd year in Poland, are supported by University of Warsaw and Humboldt University in Berlin on the basis of an exchange programme.Initiated by computer science and mathematical logic interest groups affiliated to Warsaw and Humboldt Universities in the mid-seventies of the XX century, the workshops were suspended for some years in the eighties and resumed in 1992 in the extended form of participation: they evolved from bilateral meetings to the meetings hosting researchers also from a number of countries other than Germany and Poland.The scope of subjects has been broadened too: from linguistic and logical issues initially to diverse research areas such as, for instance, the aforesaid ones.

This is the second part of the sixteenth special issue of Fundamenta Informaticae, based on the CONCURRENCY SPECIFICATION AND PROGRAMMING (CS&P) workshop, in succession to the fifteenth special issue published in 2013.This part contains 15 selected and extended versions out of 42 papers presented at the meeting that took place in Warsaw from the 25th to the 27th of September 2013.As it was the case of all the previous special issues of Fundamenta Informaticae, based on CS&P, the papers have been selected on the basis of a review process admitted by international scientific periodicals.A complete collection of the contributions has been edited by scientists of the Warsaw University and published before the workshop as Proceedings.Therefore, this is a continuation of the tradition of the former CS&P workshops, whose participants had been supplied with proceedings in the form of technical reports during the meetings.The papers contained in both the parts of the special issue cover the following topics: mathematical models of concurrent systems, parallel algorithms, model checking, multi-agent systems, rough sets, workflow systems, mereological approaches, knowledge management, knowledge discovery and data mining, neural networks, machine learning, robotics, genetic algorithms, as well as soft computing and some applications.The CS&P workshops, being held every even year in Germany and every odd year in Poland, are supported by two universities: the Warsaw University and the Humboldt University of Berlin on the basis of an exchange programme.Initiated by computer science and mathematical logic interest groups affiliated to the two universities in the mid-seventies of the XX century, the workshops were suspended for some years in the eighties and resumed in 1992 in the extended form of participation: they evolved from bilateral meetings to the meetings hosting researchers also from a number of countries other than Germany and Poland.The scope of the subjects has been broadened too: from linguistic and logical issues initially to such research areas as the ones mentioned above.

Information system of net structures based on their calculus (a distributive lattice) is introduced and, in this context, basic notions of rough set theory are re-formulated and exemplified.

In [Cza 2006] fix-point equations specifying synchronous (”hand-shaking”) communication in distributed systems have been proposed. Their solution yielded a communication network of agents, directly presented as a Petri net-like structure, and determined the global state of the specified system. The net-places represented agents, while transitions transfer of messages. A special algebra being a semi-ring with ”addition” (nondeterministic choice) and ”multiplication” (simultaneity) was a formal basis for the equations and their solving procedure. Here, the equations are modified to specify asynchronous communication, that is, such that the senders, after sending message, continue their performance without waiting for reception. This required introducing a new type of objects called buffers or mailboxes apart from the agents (senders/receivers), and changing the semi-ring into a distributive lattice of the agents and mailboxes. In the asynchronous communication, solution to the fix-point equations should determine that: (1) the sender can send message as soon as mailboxes of its simultaneous receivers can store the message, no matter whether the receivers are ready to get it or not. (2) in the resulting net, the mailboxes are included as net-places too, each one collecting messages from its senders (possibly a number of senders) and transferring them to its (exactly one) receiver for which it is the unique mailbox. The proposed modelling of communication takes some (but only some!) ideas from CSP [Hoa 1978, 1985], CCS [Mil 1980, 1989] (e.g. a concept of agents, ports, synchronization between senders and mailboxes or its absence: no synchronization between senders and receivers, communication media or channels), Petri nets [Rei 1985] (e.g. graphical presentation of solution to the communication equations) or practice of computer networks and distributed systems [C-D-K 2005] (e.g. multicasting and broadcasting,

This is the first part of the fourteenth special issue of Fundamenta Informaticae devoted to the CON-CURRENCY SPECIFICATION AND PROGRAMMING (CS&P) workshop, in succession to the thirteenth special issue published in 2011.

A protocol of mutual exclusion with FIFO discipline is devised for distributed systems with Distributed Shared Memory (DSM) and without any central server. To this end, replication of data - a principal feature of DSM is exploited. Some data consiste

This is the first part of the thirteenth special issue of Fundamenta Informaticae devoted to the

Phenomena that inherently happen in distributed computing - some types of deadlock and fairness or starvation - are examined in a client-server model. Messages travelling between clients and a server are: request for an action, permission to start it

We show that the results on analysis of net structures and transition graphs exhibited in [1] can be apllied also to generalized work flow net structures and related transition graphs.

This is the first part of the twelfth special issue of Fundamenta Informaticae devoted to the

We extend the investigation of synthesis and analysis of net structures and transition graphs to such with inhibitor relations, and show that the results obtained for the simpler case can be extended, too.

We investigate relations between transition graphs and net structures. Whereas for a given net structure there always exists a reachability graph, the inverse problem to find a net structure for a given transition graph is not solvable in general. We present sufficient and necessary conditions for several classes of transition graphs such as general, pseudo-bounded, bounded and elementary transition graphs, corresponding to general and (pseudo-)bounded P/T nets or C/E nets. We also give maximal and minimal solutions within an algebraic structure of net structures. The entire investigation is formulated in the framework of multiset theory.

In this paper we define a certain class of process languages viewing processes as bipartite graphs with an associative operation (sequential composition) on them. They describe finite evolutions of Petri nets. When extended to sets, we get an ω-complete semiring such that rational, linear, and algebraic sets of such processes can be defined as least fixed points of systems of equations. With a norm of processes also iteration lemmata can be obtained. Finally, we also present a related structure of directed acyclic graphs.

Synthesis of elementary Petri net from a given process language (given by an expression in an algebra resembling the algebra of regular languages) is posed and solved. A necessary and sufficient condition for existence of such net is proved.

It is shown how control aspects of the CSP-like communication mechanism may be represented as cause-effect structures, by using their calculus. A correctness proof of this transformation, i.e. its preserving of behaviour, has been given. A CSP-like parallel combinator for c-e structures is proposed, as well as its semantic counterpart. Compositionality property is proved.

It is shown that minimal-time singly-valued (counterparts of 1-safe Petri nets) cause-effect (c-e) structures are of the same expressive power as no-time singly-valued c-e structures, while maximal-time multi-valued c-e structures are of essentially greater expressive power than no-time multi-valued c-e structures.