59,609 research outputs found
Dynamic Consistency of Conditional Simple Temporal Networks via Mean Payoff Games: a Singly-Exponential Time DC-Checking
Conditional Simple Temporal Network (CSTN) is a constraint-based
graph-formalism for conditional temporal planning. It offers a more flexible
formalism than the equivalent CSTP model of Tsamardinos, Vidal and Pollack,
from which it was derived mainly as a sound formalization. Three notions of
consistency arise for CSTNs and CSTPs: weak, strong, and dynamic. Dynamic
consistency is the most interesting notion, but it is also the most challenging
and it was conjectured to be hard to assess. Tsamardinos, Vidal and Pollack
gave a doubly-exponential time algorithm for deciding whether a CSTN is
dynamically-consistent and to produce, in the positive case, a dynamic
execution strategy of exponential size. In the present work we offer a proof
that deciding whether a CSTN is dynamically-consistent is coNP-hard and provide
the first singly-exponential time algorithm for this problem, also producing a
dynamic execution strategy whenever the input CSTN is dynamically-consistent.
The algorithm is based on a novel connection with Mean Payoff Games, a family
of two-player combinatorial games on graphs well known for having applications
in model-checking and formal verification. The presentation of such connection
is mediated by the Hyper Temporal Network model, a tractable generalization of
Simple Temporal Networks whose consistency checking is equivalent to
determining Mean Payoff Games. In order to analyze the algorithm we introduce a
refined notion of dynamic-consistency, named \epsilon-dynamic-consistency, and
present a sharp lower bounding analysis on the critical value of the reaction
time \hat{\varepsilon} where the CSTN transits from being, to not being,
dynamically-consistent. The proof technique introduced in this analysis of
\hat{\varepsilon} is applicable more in general when dealing with linear
difference constraints which include strict inequalities
Towards formal models and languages for verifiable Multi-Robot Systems
Incorrect operations of a Multi-Robot System (MRS) may not only lead to
unsatisfactory results, but can also cause economic losses and threats to
safety. These threats may not always be apparent, since they may arise as
unforeseen consequences of the interactions between elements of the system.
This call for tools and techniques that can help in providing guarantees about
MRSs behaviour. We think that, whenever possible, these guarantees should be
backed up by formal proofs to complement traditional approaches based on
testing and simulation.
We believe that tailored linguistic support to specify MRSs is a major step
towards this goal. In particular, reducing the gap between typical features of
an MRS and the level of abstraction of the linguistic primitives would simplify
both the specification of these systems and the verification of their
properties. In this work, we review different agent-oriented languages and
their features; we then consider a selection of case studies of interest and
implement them useing the surveyed languages. We also evaluate and compare
effectiveness of the proposed solution, considering, in particular, easiness of
expressing non-trivial behaviour.Comment: Changed formattin
State-of-the-art on evolution and reactivity
This report starts by, in Chapter 1, outlining aspects of querying and updating resources on
the Web and on the Semantic Web, including the development of query and update languages
to be carried out within the Rewerse project.
From this outline, it becomes clear that several existing research areas and topics are of
interest for this work in Rewerse. In the remainder of this report we further present state of
the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give
an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs;
in Chapter 4 event-condition-action rules, both in the context of active database systems and
in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks
Enterprise modeling:process and REA value chain perspective
The paper focuses on enterprise business value chain modeling as an alternative to business process modeling. Well known REA methodology proposed by McCarthy and Geerts is used as the basic modeling framework. The research presented in the paper results in a generic semantic enterprise model using REA ontology. This rather static model is then converted into UML activity, sequence and state diagrams thus achieving dynamic view of the REA model. The dynamic REA view connects the process model and the value chain perspectives. It is shown that by using REA model transition called dynamization not only process models at task level can be achieved but also a consistency check of the REA model can be accomplished. By means of step by step value chain modeling of the enterprise a consistent process model can be reached preserving all advantages of the typical business process modeling methodsProcess model; Value chain model; REA; Production planning
XSRL: An XML web-services request language
One of the most serious challenges that web-service enabled e-marketplaces face is the lack of formal support for expressing service requests against UDDI-resident web-services in order to solve a complex business problem. In this paper we present a web-service request language (XSRL) developed on the basis of AI planning and the XML database query language XQuery. This framework is designed to handle and execute XSRL requests and is capable of performing planning actions under uncertainty on the basis of refinement and revision as new service-related information is accumulated (via interaction with the user or UDDI) and as execution circumstances necessitate change
Verification of Uncertain POMDPs Using Barrier Certificates
We consider a class of partially observable Markov decision processes
(POMDPs) with uncertain transition and/or observation probabilities. The
uncertainty takes the form of probability intervals. Such uncertain POMDPs can
be used, for example, to model autonomous agents with sensors with limited
accuracy, or agents undergoing a sudden component failure, or structural damage
[1]. Given an uncertain POMDP representation of the autonomous agent, our goal
is to propose a method for checking whether the system will satisfy an optimal
performance, while not violating a safety requirement (e.g. fuel level,
velocity, and etc.). To this end, we cast the POMDP problem into a switched
system scenario. We then take advantage of this switched system
characterization and propose a method based on barrier certificates for
optimality and/or safety verification. We then show that the verification task
can be carried out computationally by sum-of-squares programming. We illustrate
the efficacy of our method by applying it to a Mars rover exploration example.Comment: 8 pages, 4 figure
Search based software engineering: Trends, techniques and applications
© ACM, 2012. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version is available from the link below.In the past five years there has been a dramatic increase in work on Search-Based Software Engineering (SBSE), an approach to Software Engineering (SE) in which Search-Based Optimization (SBO) algorithms are used to address problems in SE. SBSE has been applied to problems throughout the SE lifecycle, from requirements and project planning to maintenance and reengineering. The approach is attractive because it offers a suite of adaptive automated and semiautomated solutions in situations typified by large complex problem spaces with multiple competing and conflicting objectives.
This article provides a review and classification of literature on SBSE. The work identifies research trends and relationships between the techniques applied and the applications to which they have been applied and highlights gaps in the literature and avenues for further research.EPSRC and E
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