Sharad C. Seth

A prototype document image analysis system for technical journals

Gobbledoc, a system providing remote access to stored documents, which is based on syntactic document analysis and optical character recognition (OCR), is discussed. In Gobbledoc, image processing, document analysis, and OCR operations take place in batch mode when the documents are acquired. The document image acquisition process and the knowledge base that must be entered into the system to process a family of page images are described. The process by which the X-Y tree data structure converts a 2-D page-segmentation problem into a series of 1-D string-parsing problems that can be tackled using conventional compiler tools is also described. Syntactic analysis is used in Gobbledoc to divide each page into labeled rectangular blocks. Blocks labeled text are converted by OCR to obtain a secondary (ASCII) document representation. Since such symbolic files are better suited for computerized search than for human access to the document content and because too many visual layout clues are lost in the OCR process (including some special characters), Gobbledoc preserves the original block images for human browsing. Storage, networking, and display issues specific to document images are also discussed.<<ETX>>

Syntactic segmentation and labeling of digitized pages from technical journals

A method for extracting alternating horizontal and vertical projection profiles are from nested sub-blocks of scanned page images of technical documents is discussed. The thresholded profile strings are parsed using the compiler utilities Lex and Yacc. The significant document components are demarcated and identified by the recursive application of block grammars. Backtracking for error recovery and branch and bound for maximum-area labeling are implemented with Unix Shell programs. Results of the segmentation and labeling process are stored in a labeled x-y tree. It is shown that families of technical documents that share the same layout conventions can be readily analyzed. Results from experiments in which more than 20 types of document entities were identified in sample pages from two journals are presented. >

A feature-based approach to conflation of geospatial sources

A Geographic Information System (GIS) populated with disparate data sources has multiple and different representations of the same real-world object. Often, the type of information in these sources is different, and combining them to generate one composite representation has many benefits. The first step in this conflation process is to identify the features in different sources that represent the same real-world entity. The matching process is not simple, since the identified features from different sources do not always match in their location, extent, and description. We present a new approach to matching GIS features from disparate sources. A graph theoretic approach is used to model the geographic context and to determine the matching features from multiple sources. Experiments on implementation of this approach demonstrate its viability.

Fault coverage requirement in production testing of LSI circuits

A technique is described for evaluating the effectiveness of production tests for large scale integrated (LSI) circuit chips. It is based on a model for the distribution of faults on a chip. The model requires two parameters, the average number (n/SUB 0/) of faults on a faulty chip and the yield (y) of good chips. It is assumed that the yield either is known or can be calculated from the available formulas. The other parameter, n/SUB 0/, is determined from an experimental procedure. Once the model is fully characterized, it allows calculation of the field reject rate as a function of the fault coverage. The technique implicitly takes into account such variables as fault simulator characteristics, the feature size, and the manufacturing environment. An actual LSI circuit is used as an example.

DOCUMENT ANALYSIS WITH AN EXPERT SYSTEM

With the decreasing cost of secondary storage it is becoming attractive to store optically scanned technical documents such as reports and articles in digital form as an array of pixels. The array may be compressed with techniques based on run-length coding. In many applications, it is desirable to access only a portion of the document, such as the title, author, abstract, or bibliography. With a knowledge base comprising layout and composition rules for specific classes of documents, these documents may be automatically subdivided into nested rectangles corresponding to meaningful blocks. The resulting structure is represented as a tree. An algorithm is proposed for assigning labels to the blocks according to their location, extent, and relative position with respect to other (possibly already labeled) blocks.

A statistical theory of digital circuit testability

A relation between the average fault coverage and circuit testability is developed. The statistical formulation allows computation of coverage for deterministic and random vectors. The following applications of this analysis are discussed: determination of circuit testability from fault simulation, coverage prediction from testability analysis, prediction of test length, and test generation by fault sampling. >

Decoding Substitution Ciphers by Means of Word Matching with Application to OCR

A substitution cipher consists of a block of natural language text where each letter of the alphabet has been replaced by a distinct symbol. As a problem in cryptography, the substitution cipher is of limited interest, but it has an important application in optical character recognition. Recent advances render it quite feasible to scan documents with a fairly complex layout and to classify (cluster) the printed characters into distinct groups according to their shape. However, given the immense variety of type styles and forms in current use, it is not possible to assign alphabetical identities to characters of arbitrary size and typeface. This gap can be bridged by solving the equivalent of a substitution cipher problem, thereby opening up the possibility of automatic translation of a scanned document into a standard character code, such as ASCII. Earlier methods relying on letter n-gram frequencies require a substantial amount of ciphertext for accurate n-gram estimates. A dictionary-based approach solves the problem using relatively small ciphertext samples and a dictionary of fewer than 500 words. Our heuristic backtrack algorithm typically visits only a few hundred among the 26! possible nodes on sample texts ranging from 100 to 600 words.

Characterizing the LSI Yield Equation from Wafer Test Data

The results of production test on LSI wafers are analyzed to determine the parameters of the yield equation. Recognizing that a physical defect on a chip can produce several logical faults, the number of faults per defect is assumed to be a random variable with Poisson distribution. The analysis provides a relationship between the yield of the tested fraction of the chip area and the cumulative fault coverage of test patterns. The parameters of the yield equation are estimated by fitting this relation to the measured yield versus fault coverage data.

A system for recognizing a large class of engineering drawings

We present a system for recognizing a large class of engineering drawings characterized by alternating instances of symbols and connection lines. The class includes domains such as flowcharts, logic and electrical circuits, and chemical plant diagrams. The output of the system, a netlist identifying the symbol types and interconnections, may be used for design simulation or as a compact portable representation of the drawing. The automatic recognition task is divided into two stages: 1) domain-independent rules are used to segment symbols from connection lines in the drawing image that has been thinned, vectorized, and preprocessed in routine ways; 2) a drawing understanding subsystem works in concert with a set of domain-specific matchers to classify symbols and correct errors automatically. A graphical user interface is provided to correct residual errors interactively and to log data for reporting errors objectively. The system has been tested on a database of 64 printed images drawn from text books and handbooks in different domains and scanned at 150 and 300 dpi resolution.

An experimental study on reject ratio prediction for VLSI circuits: Kokomo revisited

The authors report on an experiment to verify the accuracy of reject ratio predictions by the available approaches. The data collection effort includes instrumenting the wafer probe test to obtain chip failures as a function of applied vectors and running a fault simulator to obtain the cumulative fault coverage of these vectors. The accuracy of reject ratio predictions is judged by assuming earlier stopping points for the wafer probe, thereby gaining a measure of confidence in the final predicted value. The results of five different analyses are reported for over 70000 tested dies of a CMOS VLSI device. The five methods discussed predicted values for the reject ratio that vary by an order of magnitude at high values of fault coverage. It is shown that, with only an incremental effort during wafer probe, data collection that can be used to compare the relative accuracy of different models over a range of fault coverage is possible.<<ETX>>