216 research outputs found
A true concurrent model of smart contracts executions
The development of blockchain technologies has enabled the trustless
execution of so-called smart contracts, i.e. programs that regulate the
exchange of assets (e.g., cryptocurrency) between users. In a decentralized
blockchain, the state of smart contracts is collaboratively maintained by a
peer-to-peer network of mutually untrusted nodes, which collect from users a
set of transactions (representing the required actions on contracts), and
execute them in some order. Once this sequence of transactions is appended to
the blockchain, the other nodes validate it, re-executing the transactions in
the same order. The serial execution of transactions does not take advantage of
the multi-core architecture of modern processors, so contributing to limit the
throughput. In this paper we propose a true concurrent model of smart contract
execution. Based on this, we show how static analysis of smart contracts can be
exploited to parallelize the execution of transactions.Comment: Full version of the paper presented at COORDINATION 202
Minimalist Architecture to Generate Embedded System Web User Interfaces
Part 9: Embedded Systems and Petri NetsInternational audienceThis paper presents a new architecture to semi-automatically generate Web user interfaces for Embedded Systems designed using IOPT Petri Net models. The user interfaces can be used to remotely control, monitor and debug embedded systems using a standard Web Browser. The proposed architecture takes advantage of the distributed nature of the Internet to store all static user interface data and software on third-party Web services (the Cloud), and execute the user-interface code on the user’s Web Browser. A simplified protocol is proposed to enable remote control, status-monitoring, debugging and step-by-step execution, minimizing resource consumption on the physical embedded devices, including processing load, memory and communication bandwidth. As the user interface data and code are kept on third-party Web services, these resources can be shared among multiple embedded device units, and the hardware requirements to implement the devices can be simplified, leading to reduced cost solutions. To prevent down-time due to network problems or server failures, a fault-tolerant topology is suggested. The distributed architecture is transparent to end-users, observing just a Web interface for an embedded device on the other side of an Internet URL
Learning about knowledge: A complex network approach
This article describes an approach to modeling knowledge acquisition in terms
of walks along complex networks. Each subset of knowledge is represented as a
node, and relations between such knowledge are expressed as edges. Two types of
edges are considered, corresponding to free and conditional transitions. The
latter case implies that a node can only be reached after visiting previously a
set of nodes (the required conditions). The process of knowledge acquisition
can then be simulated by considering the number of nodes visited as a single
agent moves along the network, starting from its lowest layer. It is shown that
hierarchical networks, i.e. networks composed of successive interconnected
layers, arise naturally as a consequence of compositions of the prerequisite
relationships between the nodes. In order to avoid deadlocks, i.e. unreachable
nodes, the subnetwork in each layer is assumed to be a connected component.
Several configurations of such hierarchical knowledge networks are simulated
and the performance of the moving agent quantified in terms of the percentage
of visited nodes after each movement. The Barab\'asi-Albert and random models
are considered for the layer and interconnecting subnetworks. Although all
subnetworks in each realization have the same number of nodes, several
interconnectivities, defined by the average node degree of the interconnection
networks, have been considered. Two visiting strategies are investigated:
random choice among the existing edges and preferential choice to so far
untracked edges. A series of interesting results are obtained, including the
identification of a series of plateaux of knowledge stagnation in the case of
the preferential movements strategy in presence of conditional edges.Comment: 18 pages, 19 figure
Partial order and contextual net semantics for atomic and locally atomic CC programs
We present two concurrent semantics (i.e. semantics where concurrency is explicitely represented) for CC programs with atomic tells. One is based on simple partial orders of computation steps, while the other one is based on contextual nets and it is an extensión of a previous one for eventual CC programs. Both such semantics allow us to derive concurrency, dependency, and nondeterminism information for the considered languages. We prove some properties about the relation between the two semantics, and also about the relation between them and the operational semantics. Moreover, we discuss how to use the contextual net semantics in the context of CLP programs. More precisely, by interpreting concurrency as possible parallelism, our semantics can be useful for a safe parallelization of some CLP computation steps. Dually, the dependency information may also be interpreted as necessary
sequentialization, thus possibly exploiting it for the task of scheduling CC programs. Moreover, our semantics is also suitable for CC programs with a new kind of atomic tell (called locally atomic tell), which checks for consistency only the constraints it depends on. Such a tell achieves a reasonable trade-off between efficiency and atomicity, since the checked constraints can be stored in a local memory and are thus easily accessible even in a distributed implementation
Фізико-хімічна геотехнологія
Розглянуто принципові засади геотехнологічного видобування різнома-
нітних корисних копалин. Викладено питання розкриття та підготовки родовищ
за допомогою свердловинної розробки, проаналізовано способи буріння і кріп-
лення геотехнологічних свердловин, а такж застосоване обладнання. Розкрито
сутність технологічних процесів, які виконуються при диспергуванні гірських
порід, розчиненні солей, вилуговуванні металів, підземній виплавці сірки і га-
зифікації вугілля, видобуванні в’язкої нафти та сланцьового газу.
Навчальний посібник призначений для студентів, які навчаються за спе-
ціальністю «Розробка родовищ та видобування корисних копалин», а також для
студентів інших спеціальностей гірничих вузів і факультетів та інженерно-
технічних працівників підприємств і проектних організацій гірничовидобувних
галузей промисловості України
jFuzzyLogic: a Java Library to Design Fuzzy Logic Controllers According to the Standard for Fuzzy Control Programming
Fuzzy Logic Controllers are a specific model of Fuzzy Rule Based Systems suitable for engineering
applications for which classic control strategies do not achieve good results or for when it is too difficult
to obtain a mathematical model. Recently, the International Electrotechnical Commission has published
a standard for fuzzy control programming in part 7 of the IEC 61131 norm in order to offer a well defined
common understanding of the basic means with which to integrate fuzzy control applications in control
systems. In this paper, we introduce an open source Java library called jFuzzyLogic which offers a fully
functional and complete implementation of a fuzzy inference system according to this standard, providing
a programming interface and Eclipse plugin to easily write and test code for fuzzy control applications.
A case study is given to illustrate the use of jFuzzyLogic.McGill Uninversity, Genome QuebecSpanish Government
TIN2011-28488Andalusian Government
P10-TIC-685
Service orchestration with priority constraints
Business process management is an operational management approach that focuses on improving business processes. Business processes, i.e., collections of important activities in an organization, are represented in the form of a workflow, an orchestrated and repeatable pattern of activities amenable to automated analysis and control. Priority is an important concept in modeling workflows. We need priority to model cancelable and compensable tasks within transactional business processes. We use the Reo coordination language to model and formally analyze workflows. In this paper, we propose a constraint-based approach to formalize priority in Reo. We introduce special channels to propagate and block priority flows, define their semantics as constraints, and model priority propagation as a constraint satisfaction problem
Reversibility in Chemical Reactions
open access bookIn this chapter we give an overview of techniques for the
modelling and reasoning about reversibility of systems, including outof-
causal-order reversibility, as it appears in chemical reactions. We consider
the autoprotolysis of water reaction, and model it with the Calculus
of Covalent Bonding, the Bonding Calculus, and Reversing Petri Nets.
This exercise demonstrates that the formalisms, developed for expressing
advanced forms of reversibility, are able to model autoprotolysis of
water very accurately. Characteristics and expressiveness of the three
formalisms are discussed and illustrated
Comparing Petri Net and Activity Diagram Variants for Workflow Modelling:A Quest for Reactive Petri Nets
Petri net variants are widely used as a workflow modelling technique. Recently, UMLa ctivity diagrams have been used for the same purpose, even though the syntax and semantics of activity diagrams has not been yet fully worked out. Nevertheless, activity diagrams seem very similar to Petri nets and on the surface, one may think that they are variants of each other. To substantiate or deny this claim, we need to formalise the intended semantics of activity diagrams and then compare this with various Petri net semantics. In previous papers we have defined two formal semantics for UMLact ivity diagrams that are intended for workflow modelling. In this paper, we discuss the design choices that underlie these two semantics and investigate whether these design choices can be met in low-level and high-level Petri net semantics. We argue that the main difference between the Petri net semantics and our semantics of UML act ivity diagrams is that the Petri net semantics models resource usage of closed, active systems that are non-reactive, whereas our semantics of UMLact ivity diagrams models open, reactive systems. Since workflow systems are open, reactive systems, we conclude that Petri nets cannot model workflows accurately, unless they are extended with a syntax and semantics for reactivity
On deducing causality in metabolic networks
© 2008 Bodei et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution Licens
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