Results 1  10
of
34
Wrapper Induction for Information Extraction
, 1997
"... The Internet presents numerous sources of useful informationtelephone directories, product catalogs, stock quotes, weather forecasts, etc. Recently, many systems have been built that automatically gather and manipulate such information on a user's behalf. However, these resources are usually form ..."
Abstract

Cited by 519 (30 self)
 Add to MetaCart
The Internet presents numerous sources of useful informationtelephone directories, product catalogs, stock quotes, weather forecasts, etc. Recently, many systems have been built that automatically gather and manipulate such information on a user's behalf. However, these resources are usually formatted for use by people (e.g., the relevant content is embedded in HTML pages), so extracting their content is difficult. Wrappers are often used for this purpose. A wrapper is a procedure for extracting a particular resource's content. Unfortunately, handcoding wrappers is tedious. We introduce wrapper induction, a technique for automatically constructing wrappers. Our techniques can be described in terms of three main contributions. First, we pose the problem of wrapper construction as one of inductive learn...
Wrapper Induction: Efficiency and Expressiveness
 Artificial Intelligence
, 2000
"... The Internet presents numerous sources of useful informationtelephone directories, product catalogs, stock quotes, event listings, etc. Recently, many systems have been built that automatically gather and manipulate such information on a user's behalf. However, these resources are usually formatt ..."
Abstract

Cited by 210 (12 self)
 Add to MetaCart
The Internet presents numerous sources of useful informationtelephone directories, product catalogs, stock quotes, event listings, etc. Recently, many systems have been built that automatically gather and manipulate such information on a user's behalf. However, these resources are usually formatted for use by people (e.g., the relevant content is embedded in HTML pages), so extracting their content is difficult. Most systems use customized wrapper procedures to perform this extraction task. Unfortunately, writing wrappers is tedious and errorprone. As an alternative, we advocate wrapper induction, a technique for automatically constructing wrappers. In this article, we describe six wrapper classes, and use a combination of empirical and analytical techniques to evaluate the computational tradeoffs among them. We first consider expressiveness: how well the classes can handle actual Internet resources, and the extent to which wrappers in one class can mimic those in another. We then...
PACLearnability of Determinate Logic Programs
, 1992
"... The field of Inductive Logic Programming (ILP) is concerned with inducing logic programs from examples in the presence of background knowledge. This paper defines the ILP problem, and describes the various syntactic restrictions that are commonly used for learning firstorder representations. We the ..."
Abstract

Cited by 73 (7 self)
 Add to MetaCart
The field of Inductive Logic Programming (ILP) is concerned with inducing logic programs from examples in the presence of background knowledge. This paper defines the ILP problem, and describes the various syntactic restrictions that are commonly used for learning firstorder representations. We then derive some positive results concerning the learnability of these restricted classes of logic programs, by reducing the ILP problem to a standard propositional learning problem. More specifically, kclause predicate definitions consisting of determinate, functionfree, nonrecursive Horn clauses with variables of bounded depth are polynomially learnable under a broad class of probability distributions, called simple distributions. Similarly, recursive kclause definitions are polynomially learnable under simple distributions if we allow existential and membership queries about the target concept.
A bound on the label complexity of agnostic active learning
 In Proc. of the 24th international conference on Machine learning
, 2007
"... We study the label complexity of poolbased active learning in the agnostic PAC model. Specifically, we derive general bounds on the number of label requests made by the A 2 algorithm proposed by Balcan, Beygelzimer & Langford (Balcan et al., 2006). This represents the first nontrivial generalpurpo ..."
Abstract

Cited by 63 (9 self)
 Add to MetaCart
We study the label complexity of poolbased active learning in the agnostic PAC model. Specifically, we derive general bounds on the number of label requests made by the A 2 algorithm proposed by Balcan, Beygelzimer & Langford (Balcan et al., 2006). This represents the first nontrivial generalpurpose upperboundonlabelcomplexityintheagnostic PAC model. 1.
Learning Simple Concepts Under Simple Distributions
 SIAM JOURNAL OF COMPUTING
, 1991
"... We aim at developing a learning theory where `simple' concepts are easily learnable. In Valiant's learning model, many concepts turn out to be too hard (like NP hard) to learn. Relatively few concept classes were shown to be learnable polynomially. In daily life, it seems that things we care to le ..."
Abstract

Cited by 56 (3 self)
 Add to MetaCart
We aim at developing a learning theory where `simple' concepts are easily learnable. In Valiant's learning model, many concepts turn out to be too hard (like NP hard) to learn. Relatively few concept classes were shown to be learnable polynomially. In daily life, it seems that things we care to learn are usually learnable. To model the intuitive notion of learning more closely, we do not require that the learning algorithm learns (polynomially) under all distributions, but only under all simple distributions. A distribution is simple if it is dominated by an enumerable distrib...
Statistical Queries and Faulty PAC Oracles
 In Proceedings of the Sixth Annual ACM Workshop on Computational Learning Theory
, 1993
"... In this paper we study learning in the PAC model of Valiant [18] in which the example oracle used for learning may be faulty in one of two ways: either by misclassifying the example or by distorting the distribution of examples. We first consider models in which examples are misclassified. Kearns [1 ..."
Abstract

Cited by 40 (6 self)
 Add to MetaCart
In this paper we study learning in the PAC model of Valiant [18] in which the example oracle used for learning may be faulty in one of two ways: either by misclassifying the example or by distorting the distribution of examples. We first consider models in which examples are misclassified. Kearns [12] recently showed that efficient learning in a new model using statistical queries is a sufficient condition for PAC learning with classification noise. We show that efficient learning with statistical queries is sufficient for learning in the PAC model with malicious error rate proportional to the required statistical query accuracy. One application of this result is a new lower bound for tolerable malicious error in learning monomials of k literals. This is the first such bound which is independent of the number of irrelevant attributes n. We also use the statistical query model to give sufficient conditions for using distribution specific algorithms on distributions outside their prescr...
Probably Approximately Correct Learning
 Proceedings of the Eighth National Conference on Artificial Intelligence
, 1990
"... This paper surveys some recent theoretical results on the efficiency of machine learning algorithms. The main tool described is the notion of Probably Approximately Correct (PAC) learning, introduced by Valiant. We define this learning model and then look at some of the results obtained in it. We th ..."
Abstract

Cited by 40 (1 self)
 Add to MetaCart
This paper surveys some recent theoretical results on the efficiency of machine learning algorithms. The main tool described is the notion of Probably Approximately Correct (PAC) learning, introduced by Valiant. We define this learning model and then look at some of the results obtained in it. We then consider some criticisms of the PAC model and the extensions proposed to address these criticisms. Finally, we look briefly at other models recently proposed in computational learning theory. 2 Introduction It's a dangerous thing to try to formalize an enterprise as complex and varied as machine learning so that it can be subjected to rigorous mathematical analysis. To be tractable, a formal model must be simple. Thus, inevitably, most people will feel that important aspects of the activity have been left out of the theory. Of course, they will be right. Therefore, it is not advisable to present a theory of machine learning as having reduced the entire field to its bare essentials. All ...
Active learning using arbitrary binary valued queries
 Machine Learning
, 1993
"... Abstract. The original and most widely studied PAC model for learning assumes a passive learner in the sense that the learner plays no role in obtaining information about the unknown concept. That is, the samples are simply drawn independently from some probability distribution. Some work has been d ..."
Abstract

Cited by 26 (1 self)
 Add to MetaCart
Abstract. The original and most widely studied PAC model for learning assumes a passive learner in the sense that the learner plays no role in obtaining information about the unknown concept. That is, the samples are simply drawn independently from some probability distribution. Some work has been done on studying more powerful oracles and how they affect learnability. To find bounds on the improvement in sample complexity that can be expected from using oracles, we consider active learning in the sense that the learner has complete control over the information received. Specifically, we allow the learner to ask arbitrary yes/no questions. We consider both active learning under a fixed distribution and distributionfree active learning. In the case of active learning, the underlying probability distribution is used only to measure distance between concepts. For learnability with respect to a fixed distribution, active learning does not enlarge the set of learnable concept classes, but can improve the sample complexity. For distributionfree learning, it is shown that a concept class is actively learnable iff it is finite, so that active learning is in fact less powerful than the usual passive learning model. We also consider a form of distributionfree learning in which the learner knows the distribution being used, so that "distributionfree" refers only to the requirement that a bound on the number of queries can be obtained uniformly over all distributions. Even with the side information of the distribution being used, a concept class is actively learnable iff it has finite VC dimension, so that active learning with the side information still does not enlarge the set of learnable concept classes. Keywords: PAClearning, active learning, queries, oracles 1.
Probabilistic Analysis of Learning in Artificial Neural Networks: The PAC Model and its Variants
, 1997
"... There are a number of mathematical approaches to the study of learning and generalization in artificial neural networks. Here we survey the `probably approximately correct' (PAC) model of learning and some of its variants. These models provide a probabilistic framework for the discussion of generali ..."
Abstract

Cited by 18 (4 self)
 Add to MetaCart
There are a number of mathematical approaches to the study of learning and generalization in artificial neural networks. Here we survey the `probably approximately correct' (PAC) model of learning and some of its variants. These models provide a probabilistic framework for the discussion of generalization and learning. This survey concentrates on the sample complexity questions in these models; that is, the emphasis is on how many examples should be used for training. Computational complexity considerations are briefly discussed for the basic PAC model. Throughout, the importance of the VapnikChervonenkis dimension is highlighted. Particular attention is devoted to describing how the probabilistic models apply in the context of neural network learning, both for networks with binaryvalued output and for networks with realvalued output.
Theoretical Foundations of Active Learning
, 2009
"... are those of the author and should not be interpreted as representing the official policies, either expressed or implied, I study the informational complexity of active learning in a statistical learning theory framework. Specifically, I derive bounds on the rates of convergence achievable by active ..."
Abstract

Cited by 16 (8 self)
 Add to MetaCart
are those of the author and should not be interpreted as representing the official policies, either expressed or implied, I study the informational complexity of active learning in a statistical learning theory framework. Specifically, I derive bounds on the rates of convergence achievable by active learning, under various noise models and under general conditions on the hypothesis class. I also study the theoretical advantages of active learning over passive learning, and develop procedures for transforming passive learning algorithms into active learning algorithms with asymptotically superior label complexity. Finally, I study generalizations of active learning to more general forms of interactive statistical learning. viAcknowledgments There are so many people I am indebted to for helping to make this thesis, and indeed my entire career, possible. To begin, I am grateful to the faculty of Webster University, where my journey into science truly began. Support from the teachers I was privileged to have there, including Gary Coffman, BrittMarie Schiller, Ed and Anna B. Sakurai, and John Aleshunas, to name a few, inspired in me a deep curiosity