1,720,991 research outputs found
Safe LTL Assumption-Based Planning
No full textPlanning for partially observable, nondeterministic domains
is a very significant and computationally hard problem.
Often, reasonable assumptions can be drawn over expected/
nominal dynamics of the domain; using them to
constrain the search may lead to dramatically improve the
efficiency in plan generation. In turn, the execution of
assumption-based plans must be monitored to prevent runtime
failures that may happen if assumptions turn out to
be untrue, and to replan in that case. In this paper, we
use an expressive temporal logic, LTL, to describe assumptions,
and we provide two main contributions. First, we describe
an effective, symbolic forward-chaining mechanism to
build (conditional) assumption-based plans for partially observable,
nondeterministic domains. Second, we constrain
the algorithm to generate safe plans, i.e. plans guaranteeing
that, during their execution, the monitor will be able to univocally
distinguish whether the domain behavior is one of those
planned for or not. This is crucial to inhibit any chance of
useless replanning episodes. We experimentally show that
exploiting LTL assumptions highly improves the efficiency
of plan generation, and that by enforcing safety we improve
plan execution, inhibiting useless and expensive replanning
episodes, without significantly affecting plan generation
Generating Safe Assumption-Based Plans for Partially Observable, Nondeterministic Domains
No full textReactive planning using assumptions is a well-known approach to tackle complex planning problems for nondeterministic, partially observable domains. However, assumptions may be wrong; this may cause an assumption-based plan to fail. In general, it is not possible to decide at runtime whether an assumption has failed and is putting at danger the success of the plan; thus, plan execution has to be controlled taking into account every possible success-endangering assumption failure. The possibility of tracing such failures strongly depends on the actions performed by the plan. In this paper, focusing on a simple assumption language, we provide two main contributions. First, we formally characterize "safe" assumption-based plans, i.e. plans that not only succeed whenever the assumption holds, but also guarantee that any success-endangering assumption failure is traced by a suitable monitor. In this way, replanning may be triggered only when actually needed. Second, we extend the planner in a reactive platform in order to produce safe assumption-based plans. We experimentally show that safe assumption-based (re)planning is a good alternative to its unsafe counterpart, minimizing the need for replanning while retaining the efficiency in plan generatio
Bounded-Resource Reasoning as (Strong or Classical) Planning
No full textTo appropriately configure agents so as to avoid resource exhaustion, it is necessary to determine the minimum resource (time & memory) requirements necessary to solve reasoning problems. In this paper we show how the problem of reasoning under bounded resources can be recast as a planning problem. Focusing on propositional reasoning, we propose different recasting styles, which are equally interesting, since they require solving different classes of planning problems, and allow representing different reasoner architectures. We implement our approach by automatically encoding problems for the MBP planner. Our experimental results demonstrate that even simple problems can give rise to non-trivial (and often counter intuitive) time and memory saving strategies
Model-checking memory requirements of resource-bounded reasoners
No full textMemory bounds may limit the ability of a reasoner to make inferences and therefore affect the reasoner’s use- fulness. In this paper, we propose a framework to au- tomatically verify the reasoning capabilities of proposi- tional memory-bounded reasoners which have a sequen- tial architecture. Our framework explicitly accounts for the use of memory both to store facts and to support backtracking in the course of deductions. We describe an implementation of our framework in which proof existence is recast as a strong planning problem, and present results of experiments using the MBP planner which indicate that memory bounds may not be triv- ial to infer even for simple problems, and that mem- ory bounds and length of derivations are closely inter- related
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
