342,733 research outputs found
State machines for large scale computer software and systems
A method for specifying the behavior and architecture of discrete state
systems such as digital electronic devices and software using deterministic
state machines and automata products. The state machines are represented by
sequence maps where indicates that the output of the
system is in the state reached by following the sequence of events from
the initial state. Examples provided include counters, networks, reliable
message delivery, real-time analysis of gates and latches, and
producer/consumer. Techniques for defining, parameterizing, characterizing
abstract properties, and connecting sequence functions are developed. Sequence
functions are shown to represent (possibly non-finite) Moore type state
machines and general products of state machines. The method draws on state
machine theory, automata products, and recursive functions and is ordinary
working mathematics, not involving formal methods or any foundational or
meta-mathematical techniques. Systems in which there are levels of components
that may operate in parallel or concurrently are specified in terms of function
composition
Working with simple machines
A set of examples is provided that illustrate the use of work as applied to
simple machines. The ramp, pulley, lever and hydraulic press are common
experiences in the life of a student and their theoretical analysis therefore
makes the abstract concept of work more real. The mechanical advantage of each
of these systems is also discussed so that students can evaluate their
usefulness as machines.Comment: 9 pages, 4 figure
Neurocognitive Informatics Manifesto.
Informatics studies all aspects of the structure of natural and artificial information systems. Theoretical and abstract approaches to information have made great advances, but human information processing is still unmatched in many areas, including information management, representation and understanding. Neurocognitive informatics is a new, emerging field that should help to improve the matching of artificial and natural systems, and inspire better computational algorithms to solve problems that are still beyond the reach of machines. In this position paper examples of neurocognitive inspirations and promising directions in this area are given
From Operational Semantics to Abstract Machines
We consider the problem of mechanically constructing abstract machines from operational semantics, producing intermediate-level specifications of evaluators guaranteed to be correct with respect to the operational semantics. We construct these machines by repeatedly applying correctness-preserving transformations to operational semantics until the resulting specifications have the form of abstract machines. Though not automatable in general, this approach to constructing machine implementations can be mechanized, providing machine-verified correctness proofs. As examples we present the transformation of specifications for both call-by-name and call-by-value evaluation of the untyped λ-calculus into abstract machines that implement such evaluation strategies. We also present extensions to the call-by-value machine for a language containing constructs for recursion, conditionals, concrete data types, and built-in functions. In all cases, the correctness of the derived abstract machines follows from the (generally transparent) correctness of the initial operational semantic specification and the correctness of the transformations applied
Robustness Verification of Support Vector Machines
We study the problem of formally verifying the robustness to adversarial
examples of support vector machines (SVMs), a major machine learning model for
classification and regression tasks. Following a recent stream of works on
formal robustness verification of (deep) neural networks, our approach relies
on a sound abstract version of a given SVM classifier to be used for checking
its robustness. This methodology is parametric on a given numerical abstraction
of real values and, analogously to the case of neural networks, needs neither
abstract least upper bounds nor widening operators on this abstraction. The
standard interval domain provides a simple instantiation of our abstraction
technique, which is enhanced with the domain of reduced affine forms, which is
an efficient abstraction of the zonotope abstract domain. This robustness
verification technique has been fully implemented and experimentally evaluated
on SVMs based on linear and nonlinear (polynomial and radial basis function)
kernels, which have been trained on the popular MNIST dataset of images and on
the recent and more challenging Fashion-MNIST dataset. The experimental results
of our prototype SVM robustness verifier appear to be encouraging: this
automated verification is fast, scalable and shows significantly high
percentages of provable robustness on the test set of MNIST, in particular
compared to the analogous provable robustness of neural networks
Semantic closure demonstrated by the evolution of a universal constructor architecture in an artificial chemistry
We present a novel stringmol-based artificial chemistry system modelled on the universal constructor architecture (UCA) first explored by von Neumann. In a UCA, machines interact with an abstract description of themselves to replicate by copying the abstract description and constructing the machines that the abstract description encodes. DNA-based replication follows this architecture, with DNA being the abstract description, the polymerase being the copier, and the ribosome being the principal machine in expressing what is encoded on the DNA. This architecture is semantically closed as the machine that defines what the abstract description means is itself encoded on that abstract description. We present a series of experiments with the stringmol UCA that show the evolution of the meaning of genomic material, allowing the concept of semantic closure and transitions between semantically closed states to be elucidated in the light of concrete examples. We present results where, for the first time in an in silico system, simultaneous evolution of the genomic material, copier and constructor of a UCA, giving rise to viable offspring
Instruction sequence processing operators
Instruction sequence is a key concept in practice, but it has as yet not come
prominently into the picture in theoretical circles. This paper concerns
instruction sequences, the behaviours produced by them under execution, the
interaction between these behaviours and components of the execution
environment, and two issues relating to computability theory. Positioning
Turing's result regarding the undecidability of the halting problem as a result
about programs rather than machines, and taking instruction sequences as
programs, we analyse the autosolvability requirement that a program of a
certain kind must solve the halting problem for all programs of that kind. We
present novel results concerning this autosolvability requirement. The analysis
is streamlined by using the notion of a functional unit, which is an abstract
state-based model of a machine. In the case where the behaviours exhibited by a
component of an execution environment can be viewed as the behaviours of a
machine in its different states, the behaviours concerned are completely
determined by a functional unit. The above-mentioned analysis involves
functional units whose possible states represent the possible contents of the
tapes of Turing machines with a particular tape alphabet. We also investigate
functional units whose possible states are the natural numbers. This
investigation yields a novel computability result, viz. the existence of a
universal computable functional unit for natural numbers.Comment: 37 pages; missing equations in table 3 added; combined with
arXiv:0911.1851 [cs.PL] and arXiv:0911.5018 [cs.LO]; introduction and
concluding remarks rewritten; remarks and examples added; minor error in
proof of theorem 4 correcte
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