76,314 research outputs found
Conditional Reactive Systems
We lift the notion of nested application conditions from graph transformation systems to the general categorical setting of reactive systems as defined by Leifer and Milner. This serves two purposes: first, we enrich the formalism of reactive systems by adding application conditions for rules; second, it turns out that some constructions for graph transformation systems (such as computing
weakest preconditions and strongest postconditions and showing local confluence by means of critical pair analysis) can be done very elegantly in the more general setting
Conditional Bisimilarity for Reactive Systems
Reactive systems \`a la Leifer and Milner, an abstract categorical framework
for rewriting, provide a suitable framework for deriving bisimulation
congruences. This is done by synthesizing interactions with the environment in
order to obtain a compositional semantics. We enrich the notion of reactive
systems by conditions on two levels: first, as in earlier work, we consider
rules enriched with application conditions and second, we investigate the
notion of conditional bisimilarity. Conditional bisimilarity allows us to say
that two system states are bisimilar provided that the environment satisfies a
given condition. We present several equivalent definitions of conditional
bisimilarity, including one that is useful for concrete proofs and that employs
an up-to-context technique, and we compare with related behavioural
equivalences. We instantiate reactive systems in order to obtain DPO graph
rewriting and consider a case study in this setting
Jaynes' MaxEnt, Steady State Flow Systems and the Maximum Entropy Production Principle
Jaynes' maximum entropy (MaxEnt) principle was recently used to give a
conditional, local derivation of the ``maximum entropy production'' (MEP)
principle, which states that a flow system with fixed flow(s) or gradient(s)
will converge to a steady state of maximum production of thermodynamic entropy
(R.K. Niven, Phys. Rev. E, in press). The analysis provides a steady state
analog of the MaxEnt formulation of equilibrium thermodynamics, applicable to
many complex flow systems at steady state. The present study examines the
classification of physical systems, with emphasis on the choice of constraints
in MaxEnt. The discussion clarifies the distinction between equilibrium, fluid
flow, source/sink, flow/reactive and other systems, leading into an appraisal
of the application of MaxEnt to steady state flow and reactive systems.Comment: 6 pages; paper for MaxEnt0
Conditional Bisimilarity for Reactive Systems
Reactive systems \`a la Leifer and Milner, an abstract categorical framework
for rewriting, provide a suitable framework for deriving bisimulation
congruences. This is done by synthesizing interactions with the environment in
order to obtain a compositional semantics.
We enrich the notion of reactive systems by conditions on two levels: first,
as in earlier work, we consider rules enriched with application conditions and
second, we investigate the notion of conditional bisimilarity. Conditional
bisimilarity allows us to say that two system states are bisimilar provided
that the environment satisfies a given condition.
We present several equivalent definitions of conditional bisimilarity,
including one that is useful for concrete proofs and that employs an
up-to-context technique, and we compare with related behavioural equivalences.
We consider examples based on DPO graph rewriting, an instantiation of reactive
systems
Abstract Diagnosis for Timed Concurrent Constraint programs
The Timed Concurrent Constraint Language (tccp in short) is a concurrent
logic language based on the simple but powerful concurrent constraint paradigm
of Saraswat. In this paradigm, the notion of store-as-value is replaced by the
notion of store-as-constraint, which introduces some differences w.r.t. other
approaches to concurrency. In this paper, we provide a general framework for
the debugging of tccp programs. To this end, we first present a new compact,
bottom-up semantics for the language that is well suited for debugging and
verification purposes in the context of reactive systems. We also provide an
abstract semantics that allows us to effectively implement debugging algorithms
based on abstract interpretation. Given a tccp program and a behavior
specification, our debugging approach automatically detects whether the program
satisfies the specification. This differs from other semiautomatic approaches
to debugging and avoids the need to provide symptoms in advance. We show the
efficacy of our approach by introducing two illustrative examples. We choose a
specific abstract domain and show how we can detect that a program is
erroneous.Comment: 16 page
Supporting group maintenance through prognostics-enhanced dynamic dependability prediction
Condition-based maintenance strategies adapt maintenance planning through the integration of online condition monitoring of assets. The accuracy and cost-effectiveness of these strategies can be improved by integrating prognostics predictions and grouping maintenance actions respectively. In complex industrial systems, however, effective condition-based maintenance is intricate. Such systems are comprised of repairable assets which can fail in different ways, with various effects, and typically governed by dynamics which include time-dependent and conditional events. In this context, system reliability prediction is complex and effective maintenance planning is virtually impossible prior to system deployment and hard even in the case of condition-based maintenance. Addressing these issues, this paper presents an online system maintenance method that takes into account the system dynamics. The method employs an online predictive diagnosis algorithm to distinguish between critical and non-critical assets. A prognostics-updated method for predicting the system health is then employed to yield well-informed, more accurate, condition-based suggestions for the maintenance of critical assets and for the group-based reactive repair of non-critical assets. The cost-effectiveness of the approach is discussed in a case study from the power industry
Complex Actions for Event Processing
Automatic reactions triggered by complex events have been
deployed with great success in particular domains, among
others, in algorithmic trading, the automatic reaction to realtime
analysis of marked data. However, to date, reactions
in complex event processing systems are often still limited
to mere modifications of internal databases or are realized
by means similar to remote procedure calls.
In this paper, we argue that expressive complex actions
with support for composite work
ows and integration of
so called external actions are desirable for a wide range
of real-world applications among other emergency management.
This article investigates the particularities of external
actions needed in emergency management, which are initiated
inside the event processing system but which are actually
executed by external actuators, and discuss the implications
of these particularities on composite actions. Based
on these observations, we propose versatile complex actions
with temporal dependencies and a seamless integration of
complex events and external actions. This article also investigates
how the proposed integrated approach towards
complex events and complex actions can be evaluated based
on simple reactive rules. Finally, it is shown how complex actions
can be deployed for a complex event processing system
devoted to emergency management
- …