29,349 research outputs found
On Probability Distributions for Trees: Representations, Inference and Learning
We study probability distributions over free algebras of trees. Probability
distributions can be seen as particular (formal power) tree series [Berstel et
al 82, Esik et al 03], i.e. mappings from trees to a semiring K . A widely
studied class of tree series is the class of rational (or recognizable) tree
series which can be defined either in an algebraic way or by means of
multiplicity tree automata. We argue that the algebraic representation is very
convenient to model probability distributions over a free algebra of trees.
First, as in the string case, the algebraic representation allows to design
learning algorithms for the whole class of probability distributions defined by
rational tree series. Note that learning algorithms for rational tree series
correspond to learning algorithms for weighted tree automata where both the
structure and the weights are learned. Second, the algebraic representation can
be easily extended to deal with unranked trees (like XML trees where a symbol
may have an unbounded number of children). Both properties are particularly
relevant for applications: nondeterministic automata are required for the
inference problem to be relevant (recall that Hidden Markov Models are
equivalent to nondeterministic string automata); nowadays applications for Web
Information Extraction, Web Services and document processing consider unranked
trees
A Local Logic for Realizability in Web Service Choreographies
Web service choreographies specify conditions on observable interactions
among the services. An important question in this regard is realizability:
given a choreography C, does there exist a set of service implementations I
that conform to C ? Further, if C is realizable, is there an algorithm to
construct implementations in I ? We propose a local temporal logic in which
choreographies can be specified, and for specifications in the logic, we solve
the realizability problem by constructing service implementations (when they
exist) as communicating automata. These are nondeterministic finite state
automata with a coupling relation. We also report on an implementation of the
realizability algorithm and discuss experimental results.Comment: In Proceedings WWV 2014, arXiv:1409.229
Resonance and web structure in discrete soliton systems: the two-dimensional Toda lattice and its fully discrete and ultra-discrete versions
We present a class of solutions of the two-dimensional Toda lattice equation,
its fully discrete analogue and its ultra-discrete limit. These solutions
demonstrate the existence of soliton resonance and web-like structure in
discrete integrable systems such as differential-difference equations,
difference equations and cellular automata (ultra-discrete equations).Comment: final version: several errors were correcte
Automata for Web Services Fault Monitoring and Diagnosis
Like any software, web service fault management is also required to go through different phases of fault management lifecycle. Model based diagnosis has been a well established practice for its several positive aspects including cognitively being better understood by development and testing teams. Automata is a simple and formally well defined model being used for monitoring and diagnosis of system faults. For the reason, here we have reviewed works on automata for web service fault management and also propose a model of stochastic automata for the purpose
Vision of a Visipedia
The web is not perfect: while text is easily
searched and organized, pictures (the vast majority of the bits
that one can find online) are not. In order to see how one could
improve the web and make pictures first-class citizens of the
web, I explore the idea of Visipedia, a visual interface for
Wikipedia that is able to answer visual queries and enables
experts to contribute and organize visual knowledge. Five
distinct groups of humans would interact through Visipedia:
users, experts, editors, visual workers, and machine vision
scientists. The latter would gradually build automata able to
interpret images. I explore some of the technical challenges
involved in making Visipedia happen. I argue that Visipedia will
likely grow organically, combining state-of-the-art machine
vision with human labor
Procedure-modular specification and verification of temporal safety properties
This paper describes ProMoVer, a tool for fully automated procedure-modular verification of Java programs equipped with method-local and global assertions that specify safety properties of sequences of method invocations. Modularity at the procedure-level is a natural instantiation of the modular verification paradigm, where correctness of global properties is relativized on the local properties of the methods rather than on their implementations. Here, it is based on the construction of maximal models for a program model that abstracts away from program data. This approach allows global properties to be verified in the presence of code evolution, multiple method implementations (as arising from software product lines), or even unknown method implementations (as in mobile code for open platforms). ProMoVer automates a typical verification scenario for a previously developed tool set for compositional verification of control flow safety properties, and provides appropriate pre- and post-processing. Both linear-time temporal logic and finite automata are supported as formalisms for expressing local and global safety properties, allowing the user to choose a suitable format for the property at hand. Modularity is exploited by a mechanism for proof reuse that detects and minimizes the verification tasks resulting from changes in the code and the specifications. The verification task is relatively light-weight due to support for abstraction from private methods and automatic extraction of candidate specifications from method implementations. We evaluate the tool on a number of applications from the domains of Java Card and web-based application
Piloting an Empirical Study on Measures for Workflow Similarity
Service discovery of state dependent services has to take workflow aspects into account. To increase the usability of a service discovery, the result list of services should be ordered with regard to the relevance of the services. Means of ordering a list of workflows due to their similarity with regard to a query are missing. This paper presents a pilot of an empirical study on the influence of different measures on workflow similarity. It turns out that, although preliminary, relations between different measures are indicated and that a similarity definition depends on the application scenario in which the service discovery is applied
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