5,905 research outputs found
A Probabilistic Logic Programming Event Calculus
We present a system for recognising human activity given a symbolic
representation of video content. The input of our system is a set of
time-stamped short-term activities (STA) detected on video frames. The output
is a set of recognised long-term activities (LTA), which are pre-defined
temporal combinations of STA. The constraints on the STA that, if satisfied,
lead to the recognition of a LTA, have been expressed using a dialect of the
Event Calculus. In order to handle the uncertainty that naturally occurs in
human activity recognition, we adapted this dialect to a state-of-the-art
probabilistic logic programming framework. We present a detailed evaluation and
comparison of the crisp and probabilistic approaches through experimentation on
a benchmark dataset of human surveillance videos.Comment: Accepted for publication in the Theory and Practice of Logic
Programming (TPLP) journa
The Complex Event Recognition Group
The Complex Event Recognition (CER) group is a research team, affiliated with
the National Centre of Scientific Research "Demokritos" in Greece. The CER
group works towards advanced and efficient methods for the recognition of
complex events in a multitude of large, heterogeneous and interdependent data
streams. Its research covers multiple aspects of complex event recognition,
from efficient detection of patterns on event streams to handling uncertainty
and noise in streams, and machine learning techniques for inferring interesting
patterns. Lately, it has expanded to methods for forecasting the occurrence of
events. It was founded in 2009 and currently hosts 3 senior researchers, 5 PhD
students and works regularly with under-graduate students
A General Overview of Formal Languages for Individual-Based Modelling of Ecosystems
Various formal languages have been proposed in the literature for the
individual-based modelling of ecological systems. These languages differ in
their treatment of time and space. Each modelling language offers a distinct
view and techniques for analyzing systems. Most of the languages are based on
process calculi or P systems. In this article, we present a general overview of
the existing modelling languages based on process calculi. We also discuss,
briefly, other approaches such as P systems, cellular automata and Petri nets.
Finally, we show advantages and disadvantages of these modelling languages and
we propose some future research directions.Comment: arXiv admin note: text overlap with arXiv:1610.08171 by other author
Semi-Supervised Online Structure Learning for Composite Event Recognition
Online structure learning approaches, such as those stemming from Statistical
Relational Learning, enable the discovery of complex relations in noisy data
streams. However, these methods assume the existence of fully-labelled training
data, which is unrealistic for most real-world applications. We present a novel
approach for completing the supervision of a semi-supervised structure learning
task. We incorporate graph-cut minimisation, a technique that derives labels
for unlabelled data, based on their distance to their labelled counterparts. In
order to adapt graph-cut minimisation to first order logic, we employ a
suitable structural distance for measuring the distance between sets of logical
atoms. The labelling process is achieved online (single-pass) by means of a
caching mechanism and the Hoeffding bound, a statistical tool to approximate
globally-optimal decisions from locally-optimal ones. We evaluate our approach
on the task of composite event recognition by using a benchmark dataset for
human activity recognition, as well as a real dataset for maritime monitoring.
The evaluation suggests that our approach can effectively complete the missing
labels and eventually, improve the accuracy of the underlying structure
learning system
Real-time and Probabilistic Temporal Logics: An Overview
Over the last two decades, there has been an extensive study on logical
formalisms for specifying and verifying real-time systems. Temporal logics have
been an important research subject within this direction. Although numerous
logics have been introduced for the formal specification of real-time and
complex systems, an up to date comprehensive analysis of these logics does not
exist in the literature. In this paper we analyse real-time and probabilistic
temporal logics which have been widely used in this field. We extrapolate the
notions of decidability, axiomatizability, expressiveness, model checking, etc.
for each logic analysed. We also provide a comparison of features of the
temporal logics discussed
Ensuring Liveness Properties of Distributed Systems (A Research Agenda)
Often fairness assumptions need to be made in order to establish liveness
properties of distributed systems, but in many situations these lead to false
conclusions.
This document presents a research agenda aiming at laying the foundations of
a theory of concurrency that is equipped to ensure liveness properties of
distributed systems without making fairness assumptions. This theory will
encompass process algebra, temporal logic and semantic models, as well as
treatments of real-time. The agenda also includes developing a methodology that
allows successful application of this theory to the specification, analysis and
verification of realistic distributed systems, including routing protocols for
wireless networks.
Contemporary process algebras and temporal logics fail to make distinctions
between systems of which one has a crucial liveness property and the other does
not, at least when assuming justness, a strong progress property, but not
assuming fairness. Setting up an alternative framework involves giving up on
identifying strongly bisimilar systems, inventing new induction principles,
developing new axiomatic bases for process algebras and new congruence formats
for operational semantics, and creating new treatments of time and probability.
Even simple systems like fair schedulers or mutual exclusion protocols cannot
be accurately specified in standard process algebras (or Petri nets) in the
absence of fairness assumptions. Hence the work involves the study of adequate
language or model extensions, and their expressive power
A Probabilistic Extension of Action Language BC+
We present a probabilistic extension of action language BC+. Just like BC+ is
defined as a high-level notation of answer set programs for describing
transition systems, the proposed language, which we call pBC+, is defined as a
high-level notation of LPMLN programs---a probabilistic extension of answer set
programs. We show how probabilistic reasoning about transition systems, such as
prediction, postdiction, and planning problems, as well as probabilistic
diagnosis for dynamic domains, can be modeled in pBC+ and computed using an
implementation of LPMLN.Comment: Paper presented at the 34nd International Conference on Logic
Programming (ICLP 2018), Oxford, UK, July 14 to July 17, 2018 18 pages,
LaTeX, 1 PDF figures (arXiv:YYMM.NNNNN
Knowledge and Security
Epistemic concepts, and in some cases epistemic logic, have been used in
security research to formalize security properties of systems. This survey
illustrates some of these uses by focusing on confidentiality in the context of
cryptographic protocols, and in the context of multi-level security systems.Comment: 51 pages; preliminary version of a chapter for an upcoming Handbook
of Logics for Knowledge and Belie
Reactive Reasoning with the Event Calculus
Systems for symbolic event recognition accept as input a stream of
time-stamped events from sensors and other computational devices, and seek to
identify high-level composite events, collections of events that satisfy some
pattern. RTEC is an Event Calculus dialect with novel implementation and
'windowing' techniques that allow for efficient event recognition, scalable to
large data streams. RTEC can deal with applications where event data arrive
with a (variable) delay from, and are revised by, the underlying sources. RTEC
can update already recognised events and recognise new events when data arrive
with a delay or following data revision. Our evaluation shows that RTEC can
support real-time event recognition and is capable of meeting the performance
requirements identified in a recent survey of event processing use cases.Comment: International Workshop on Reactive Concepts in Knowledge
Representation (ReactKnow 2014), co-located with the 21st European Conference
on Artificial Intelligence (ECAI 2014). Proceedings of the International
Workshop on Reactive Concepts in Knowledge Representation (ReactKnow 2014),
pages 9-15, technical report, ISSN 1430-3701, Leipzig University, 2014.
http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-150562. 2014,
AppLP: A Dialogue on Applications of Logic Programming
This document describes the contributions of the 2016 Applications of Logic
Programming Workshop (AppLP), which was held on October 17 and associated with
the International Conference on Logic Programming (ICLP) in Flushing, New York
City.Comment: David S. Warren and Yanhong A. Liu (Editors). 33 pages. Including
summaries by Christopher Kane and abstracts or position papers by M. Aref, J.
Rosenwald, I. Cervesato, E.S.L. Lam, M. Balduccini, J. Lobo, A. Russo, E.
Lupu, N. Leone, F. Ricca, G. Gupta, K. Marple, E. Salazar, Z. Chen, A. Sobhi,
S. Srirangapalli, C.R. Ramakrishnan, N. Bj{\o}rner, N.P. Lopes, A.
Rybalchenko, and P. Tara
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