18,160 research outputs found
An Integrated First-Order Theory of Points and Intervals over Linear Orders (Part II)
There are two natural and well-studied approaches to temporal ontology and
reasoning: point-based and interval-based. Usually, interval-based temporal
reasoning deals with points as a particular case of duration-less intervals. A
recent result by Balbiani, Goranko, and Sciavicco presented an explicit
two-sorted point-interval temporal framework in which time instants (points)
and time periods (intervals) are considered on a par, allowing the perspective
to shift between these within the formal discourse. We consider here two-sorted
first-order languages based on the same principle, and therefore including
relations, as first studied by Reich, among others, between points, between
intervals, and inter-sort. We give complete classifications of its
sub-languages in terms of relative expressive power, thus determining how many,
and which, are the intrinsically different extensions of two-sorted first-order
logic with one or more such relations. This approach roots out the classical
problem of whether or not points should be included in a interval-based
semantics. In this Part II, we deal with the cases of all dense and the case of
all unbounded linearly ordered sets.Comment: This is Part II of the paper `An Integrated First-Order Theory of
Points and Intervals over Linear Orders' arXiv:1805.08425v2. Therefore the
introduction, preliminaries and conclusions of the two papers are the same.
This version implements a few minor corrections and an update to the
affiliation of the second autho
A Logical Method for Policy Enforcement over Evolving Audit Logs
We present an iterative algorithm for enforcing policies represented in a
first-order logic, which can, in particular, express all transmission-related
clauses in the HIPAA Privacy Rule. The logic has three features that raise
challenges for enforcement --- uninterpreted predicates (used to model
subjective concepts in privacy policies), real-time temporal properties, and
quantification over infinite domains (such as the set of messages containing
personal information). The algorithm operates over audit logs that are
inherently incomplete and evolve over time. In each iteration, the algorithm
provably checks as much of the policy as possible over the current log and
outputs a residual policy that can only be checked when the log is extended
with additional information. We prove correctness and termination properties of
the algorithm. While these results are developed in a general form, accounting
for many different sources of incompleteness in audit logs, we also prove that
for the special case of logs that maintain a complete record of all relevant
actions, the algorithm effectively enforces all safety and co-safety
properties. The algorithm can significantly help automate enforcement of
policies derived from the HIPAA Privacy Rule.Comment: Carnegie Mellon University CyLab Technical Report. 51 page
A Theory of Sampling for Continuous-time Metric Temporal Logic
This paper revisits the classical notion of sampling in the setting of
real-time temporal logics for the modeling and analysis of systems. The
relationship between the satisfiability of Metric Temporal Logic (MTL) formulas
over continuous-time models and over discrete-time models is studied. It is
shown to what extent discrete-time sequences obtained by sampling
continuous-time signals capture the semantics of MTL formulas over the two time
domains. The main results apply to "flat" formulas that do not nest temporal
operators and can be applied to the problem of reducing the verification
problem for MTL over continuous-time models to the same problem over
discrete-time, resulting in an automated partial practically-efficient
discretization technique.Comment: Revised version, 43 pages
An Integrated First-Order Theory of Points and Intervals over Linear Orders (Part I)
There are two natural and well-studied approaches to temporal ontology and
reasoning: point-based and interval-based. Usually, interval-based temporal
reasoning deals with points as a particular case of duration-less intervals. A
recent result by Balbiani, Goranko, and Sciavicco presented an explicit
two-sorted point-interval temporal framework in which time instants (points)
and time periods (intervals) are considered on a par, allowing the perspective
to shift between these within the formal discourse. We consider here two-sorted
first-order languages based on the same principle, and therefore including
relations, as first studied by Reich, among others, between points, between
intervals, and inter-sort. We give complete classifications of its
sub-languages in terms of relative expressive power, thus determining how many,
and which, are the intrinsically different extensions of two-sorted first-order
logic with one or more such relations. This approach roots out the classical
problem of whether or not points should be included in a interval-based
semantics
Integrated Modeling and Verification of Real-Time Systems through Multiple Paradigms
Complex systems typically have many different parts and facets, with
different characteristics. In a multi-paradigm approach to modeling, formalisms
with different natures are used in combination to describe complementary parts
and aspects of the system. This can have a beneficial impact on the modeling
activity, as different paradigms an be better suited to describe different
aspects of the system. While each paradigm provides a different view on the
many facets of the system, it is of paramount importance that a coherent
comprehensive model emerges from the combination of the various partial
descriptions. In this paper we present a technique to model different aspects
of the same system with different formalisms, while keeping the various models
tightly integrated with one another. In addition, our approach leverages the
flexibility provided by a bounded satisfiability checker to encode the
verification problem of the integrated model in the propositional
satisfiability (SAT) problem; this allows users to carry out formal
verification activities both on the whole model and on parts thereof. The
effectiveness of the approach is illustrated through the example of a
monitoring system.Comment: 27 page
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Completeness, robustness, and safety in real-time software requirements specification
This paper presents an approach to providing a rigorous basis for ascertaining whether or not a given set of software requirements is internally complete, i.e., closed with respect to questions and inferences that can be made on the basis of information included in the specification. Emphasis is placed on aspects of software requirements specifications that previously have not been adequately handled, including timing abstractions, safety, and robustness
Putting time into proof outlines
A logic for reasoning about timing of concurrent programs is presented. The logic is based on proof outlines and can handle maximal parallelism as well as resource-constrained execution environments. The correctness proof for a mutual exclusion protocol that uses execution timings in a subtle way illustrates the logic in action
Method for Detecting Anomalous States of a Control Object in Information Systems Based on the Analysis of Temporal Data and Knowledge
The problem of finding the anomalous states of the control object in the management information system under conditions of uncertainty caused by the incompleteness of knowledge about this object is considered. The method of classifying the current state of the control object in real time, allowing to identify the current anomalous state. The method uses temporal data and knowledge. Data is represented by sequences of events with timestamps. Knowledge is represented as weighted temporal rules and constraints. The method includes the following key phases: the formation of sequences of logical facts; selection of temporal rules and constraints; classification based on a comparison of rules and constraints. Logical facts are represented as predicates on event attributes and reflect the state of the control object. Logical rules define valid sequences of logical facts. Performing a classification by successive comparisons of constraints and weights of the rules makes it possible to more effectively identify the anomalous state since the comparison of the constraints reduces the subset of facts comparing to the current state. The method creates conditions for improving management efficiency in the context of incomplete information on the state of a complex object by using logical inference in knowledge bases for anomalous states of such control objects
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