1,400 research outputs found
Compositional Reasoning for Explicit Resource Management in Channel-Based Concurrency
We define a pi-calculus variant with a costed semantics where channels are
treated as resources that must explicitly be allocated before they are used and
can be deallocated when no longer required. We use a substructural type system
tracking permission transfer to construct coinductive proof techniques for
comparing behaviour and resource usage efficiency of concurrent processes. We
establish full abstraction results between our coinductive definitions and a
contextual behavioural preorder describing a notion of process efficiency
w.r.t. its management of resources. We also justify these definitions and
respective proof techniques through numerous examples and a case study
comparing two concurrent implementations of an extensible buffer.Comment: 51 pages, 7 figure
Robustness of a bisimulation-type faster-than preorder
TACS is an extension of CCS where upper time bounds for delays can be
specified. Luettgen and Vogler defined three variants of bismulation-type
faster-than relations and showed that they all three lead to the same preorder,
demonstrating the robustness of their approach. In the present paper, the
operational semantics of TACS is extended; it is shown that two of the variants
still give the same preorder as before, underlining robustness. An explanation
is given why this result fails for the third variant. It is also shown that
another variant, which mixes old and new operational semantics, can lead to
smaller relations that prove the same preorder.Comment: Express Worksho
A Voting-Based System for Ethical Decision Making
We present a general approach to automating ethical decisions, drawing on
machine learning and computational social choice. In a nutshell, we propose to
learn a model of societal preferences, and, when faced with a specific ethical
dilemma at runtime, efficiently aggregate those preferences to identify a
desirable choice. We provide a concrete algorithm that instantiates our
approach; some of its crucial steps are informed by a new theory of
swap-dominance efficient voting rules. Finally, we implement and evaluate a
system for ethical decision making in the autonomous vehicle domain, using
preference data collected from 1.3 million people through the Moral Machine
website.Comment: 25 pages; paper has been reorganized, related work and discussion
sections have been expande
Three Simulation Algorithms for Labelled Transition Systems
Algorithms which compute the coarsest simulation preorder are generally
designed on Kripke structures. Only in a second time they are extended to
labelled transition systems. By doing this, the size of the alphabet appears in
general as a multiplicative factor to both time and space complexities. Let
denotes the state space, the transition relation, the
alphabet and the partition of induced by the coarsest simulation
equivalence. In this paper, we propose a base algorithm which minimizes, since
the first stages of its design, the incidence of the size of the alphabet in
both time and space complexities. This base algorithm, inspired by the one of
Paige and Tarjan in 1987 for bisimulation and the one of Ranzato and Tapparo in
2010 for simulation, is then derived in three versions. One of them has the
best bit space complexity up to now,
, while another one has the
best time complexity up to now, . Note the
absence of the alphabet in these complexities. A third version happens to be a
nice compromise between space and time since it runs in
time, with a branching factor generally
far below , and uses
bits
Reaching social consensus family budgets: The Spanish case
The study of family budgets has been traditionally used to analyse consumersâ behaviour and estimate cost-of-living since the end of 19th century. Generally speaking, the computation of the budgets has been based on two different methodologies, the prescriptive and the descriptive method. Both present several drawbacks like the comparison among different areas, family types and over time.
This paper proposes a new methodology for reaching family budgets, namely social consensus family budgets, to overcome such problems and examine the main features of the novel approach. The suggested method uses the minimization of the differences with respect to the consumerâs preferences to obtain a solution that summarizes single behaviour into a social preference. This approach is especially conceived for preferences on possibly related-expenditure groups. In addition, several algorithms are introduced to compute the social family budgets. Finally, the contribution includes the Spanish case as an example of reaching some social consensus family budgets in order to show the operational character and intuitive interpretation of the proposal approach.Este trabajo forma parte del proyecto de investigaciĂłn con financiaciĂłn nacional: MEC-FEDER Grant ECO2016-77900-
A review of multi-criteria decision making methods for enhanced maintenance delivery
Conventionally there is a strong relation between manufacturing and services in complex engineering industries. For companies which aim to last in the competitive manufacturing market choosing appropriate decision making methods to improve their maintenance delivery has a vital role. The aim of this paper is to review Multi Criteria Decision Making (MCDM) models, evaluate each method and do a critical comparison to assess them from a maintenance management point of view. The first section of this paper reviews MCDM methods in different literature, and then the second part develops a set of criteria to classify different techniques. At the end methods are compared based on developed criteria. This paper assesses different MCDM models, and provides a framework to select approaches for maintenance management
Stochastic bounds for two-layer loss systems
This paper studies multiclass loss systems with two layers of servers, where
each server at the first layer is dedicated to a certain customer class, while
the servers at the second layer can handle all customer classes. The routing of
customers follows an overflow scheme, where arriving customers are
preferentially directed to the first layer. Stochastic comparison and coupling
techniques are developed for studying how the system is affected by packing of
customers, altered service rates, and altered server configurations. This
analysis leads to easily computable upper and lower bounds for the performance
of the system.Comment: Revised conten
Conformance Testing with Labelled Transition Systems: Implementation Relations and Test Generation
This paper studies testing based on labelled transition systems, presenting two test generation algorithms with their corresponding implementation relations. The first algorithm assumes that implementations communicate with their environment via symmetric, synchronous interactions. It is based on the theory of testing equivalence and preorder, as is most of the testing theory for labelled transition systems, and it is found in the literature in some slightly different variations. The second algorithm is based on the assumption that implementations communicate with their environment via inputs and outputs. Such implementations are formalized by restricting the class of labelled transition systems to those systems that can always accept input actions. For these implementations a testing theory is developed, analogous to the theory of testing equivalence and preorder. It consists of implementation relations formalizing the notion of conformance of these implementations with respect to labelled transition system specifications, test cases and test suites, test execution, the notion of passing a test suite, and the test generation algorithm, which is proved to produce sound test suites for one of the implementation relations
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