Kazem Taghva

Recognizing acronyms and their definitions

Abstract. This paper introduces an automatic method for finding acronyms and their definitions in free text. The method is based on an inexact pattern matching algorithm applied to text surrounding the possible acronym. Evaluation shows both high recall and precision for a set of documents randomly selected from a larger set of full text documents.

Results of applying probabilistic IR to OCR text

Character accuracy of optically recognized text is considered a basic measure for evaluating OCR devices. In the broader sense, another fundamental measure of an OCR’s goodness is whether its generated text is usable for retrieving information. In this study, we evaluate retrieval effectiveness from OCR text databases using a probabilistic IR system. We compare these retrieval results to their manually corrected equivalent. We show there is no statistical difference in precision and recall using graded accuracy levels from three OCR devices. However, characteristics of the OCR data have side effects that could cause unstable results with this IR model. In particular, we found individual queries can be greatly affected. Knowing the qualities of OCR text, we compensate for them by applying an automatic post-processing system that improves effectiveness.

OCRSpell: an interactive spelling correction system for OCR errors in text

Abstract. In this paper, we describe a spelling correction system designed specifically for OCR-generated text that selects candidate words through the use of information gathered from multiple knowledge sources. This system for text correction is based on static and dynamic device mappings, approximate string matching, and n-gram analysis. Our statistically based, Bayesian system incorporates a learning feature that collects confusion information at the collection and document levels. An evaluation of the new system is presented as well.

Evaluation of model-based retrieval effectiveness with OCR text

We give a comprehensive report on our experiments with retrieval from OCR-generated text using systems based on standard models of retrieval. More specifically, we show that average precision and recall is not affected by OCR errors across systems for several collections. The collections used in these experiments include both actual OCR-generated text and standard information retrieval collections corrupted through the simulation of OCR errors. Both the actual and simulation experiments include full-text and abstract-length documents. We also demonstrate that the ranking and feedback methods associated with these models are generally not robust enough to deal with OCR errors. It is further shown that the OCR errors and garbage strings generated from the mistranslation of graphic objects increase the size of the index by a wide margin. We not only point out problems that can arise from applying OCR text within an information retrieval environment, we also suggest solutions to overcome some of these problems.

Effects of OCR errors on ranking and feedback using the vector space model

We report on the performance of the vector space model in the presence of OCR errors. We show that average precision and recall is not affected for our full text document collection when the OCR version is compared to its corresponding corrected set. We do see divergence though between the relevant document rankings of the OCR and corrected collections with different weighting combinations. In particular, we observed that cosine normalization plays a considerable role in the disparity seen between the collections. Furthermore, we show that even though feedback improves retrieval for both collections, it can not be used to compensate for OCR errors caused by badly degraded documents.

The effects of noisy data on text retrieval

We report on the results of our experiments on query evaluation in the presence of noisy data. In particular, an OCR‐generated database and its corresponding 99.8% correct version are used to process a set of queries to determine the effect the degraded version will have on retrieval. It is shown that, with the set of scientific documents we use in our testing, the effect is insignificant. We further improve the result by applying an automatic postprocessing system designed to correct the kinds of errors generated by recognition devices.

Expert system for automatically correcting OCR output

This paper describes a new expert system for automatically correcting errors made by optical character recognition (OCR) devices. The system, which we call the post-processing system, is designed to improve the quality of text produced by an OCR device in preparation for subsequent retrieval from an information system. The system is composed of numerous parts: an information retrieval system, an English dictionary, a domain-specific dictionary, and a collection of algorithms and heuristics designed to correct as many OCR errors as possible. For the remaining errors that cannot be corrected, the system passes them on to a user-level editing program. This post-processing system can be viewed as part of a larger system that would streamline the steps of taking a document from its hard copy form to its usable electronic form, or it can be considered a stand alone system for OCR error correction. An earlier version of this system has been used to process approximately 10,000 pages of OCR generated text. Among the OCR errors discovered by this version, about 87% were corrected. We implement numerous new parts of the system, test this new version, and present the results.

A stemming algorithm for the Farsi language

In this paper, we report on the design and implementation of a stemmer for the Farsi language. The results of our evaluation on a small Farsi document collection shows a significant improvement in precision/recall over not stemming.

Ontology-based classification of email

We report on the construction of an ontology that applies rules for identification of features to be used for email classification. The associated probabilities for these features are then calculated from the training set of emails and used as a part of the feature vectors for an underlying Bayesian classifier.

The effects of OCR error on the extraction of private information

OCR error has been shown not to affect the average accuracy of text retrieval or text categorization.Recent studies however have indicated that information extraction is significantly degraded by OCR error. We experimented with information extraction software on two collections, one with OCR-ed documents and another with manually-corrected versions of the former. We discovered a significant reduction in accuracy on the OCR text versus the corrected text. The majority of errors were attributable to zoning problems rather than OCR classification errors.