Predicting Appropriate Semantic Web Terms from Words

AAAI Conferences

The Semantic Web language RDF was designed to unambiguously define and use ontologies to encode data and knowledge on the Web. Many people find it difficult, however, to write complex RDF statements and queries because doing so requires familiarity with the appropriate ontologies and the terms they define. We describe a system that suggests appropriate RDF terms given semantically related English words and general domain and context information. We use the Swoogle Semantic Web search engine to provide RDF term and namespace statistics, the WorldNet lexical ontology to find semantically related words, and a naïve Bayes classifier to suggest terms. A customized graph data structure of related namespaces is constructed from Swoogle's database to speed up the classifier model learning and prediction time.


Novel Sensor Scheduling Scheme for Intruder Tracking in Energy Efficient Sensor Networks

arXiv.org Artificial Intelligence

We consider the problem of tracking an intruder using a network of wireless sensors. For tracking the intruder at each instant, the optimal number and the right configuration of sensors has to be powered. As powering the sensors consumes energy, there is a trade off between accurately tracking the position of the intruder at each instant and the energy consumption of sensors. This problem has been formulated in the framework of Partially Observable Markov Decision Process (POMDP). Even for the simplest model considered in [1], the curse of dimensionality renders the problem intractable. We formulate this problem with a suitable state-action space in the framework of POMDP and develop a reinforcement learning algorithm utilising the Upper Confidence Tree Search (UCT) method to mitigate the state-action space explosion. Through simulations, we illustrate that our algorithm scales well with the increasing state and action space.


HodgeRank with Information Maximization for Crowdsourced Pairwise Ranking Aggregation

arXiv.org Machine Learning

Recently, crowdsourcing has emerged as an effective paradigm for human-powered large scale problem solving in various domains. However, task requester usually has a limited amount of budget, thus it is desirable to have a policy to wisely allocate the budget to achieve better quality. In this paper, we study the principle of information maximization for active sampling strategies in the framework of HodgeRank, an approach based on Hodge Decomposition of pairwise ranking data with multiple workers. The principle exhibits two scenarios of active sampling: Fisher information maximization that leads to unsupervised sampling based on a sequential maximization of graph algebraic connectivity without considering labels; and Bayesian information maximization that selects samples with the largest information gain from prior to posterior, which gives a supervised sampling involving the labels collected. Experiments show that the proposed methods boost the sampling efficiency as compared to traditional sampling schemes and are thus valuable to practical crowdsourcing experiments.


HodgeRank With Information Maximization for Crowdsourced Pairwise Ranking Aggregation

AAAI Conferences

Recently, crowdsourcing has emerged as an effective paradigm for human-powered large scale problem solving in various domains. However, task requester usually has a limited amount of budget, thus it is desirable to have a policy to wisely allocate the budget to achieve better quality. In this paper, we study the principle of information maximization for active sampling strategies in the framework of HodgeRank, an approach based on Hodge Decomposition of pairwise ranking data with multiple workers. The principle exhibits two scenarios of active sampling: Fisher information maximization that leads to unsupervised sampling based on a sequential maximization of graph algebraic connectivity without considering labels; and Bayesian information maximization that selects samples with the largest information gain from prior to posterior, which gives a supervised sampling involving the labels collected. Experiments show that the proposed methods boost the sampling efficiency as compared to traditional sampling schemes and are thus valuable to practical crowdsourcing experiments.


Secure Routing in Wireless Sensor Networks via POMDPs

AAAI Conferences

Wireless sensor networks are being increasingly used for sustainable development. The task of routing in these resource-constraint networks is particularly challenging as they operate over prolonged deployment periods, necessitating optimal use of their resources. Moreover, due to the deployment in unattended environments, they become an easy target for attackers. In this paper, we propose a hierarchical POMDP based approach to make routing decisions with partial/limited information about the sensor nodes, in a secure and energy-efficient manner. We demonstrate in a large-scale simulation that the approach provides a better energy/packet delivery tradeoff than competing methods, and also validate these conclusions in a real-world testbed.