An Algorithm for Sentence Recovery from PDF Files

Abstract

The use of PDF documents in Natural Language Processing (NLP) became an almost daily activity for researchers in the field of computer linguistics and alike. Extracting plain text from PDF documents, with existing software tools, leads to severe distortion of sentence and paragraph structures, which is a huge problem for linguistically oriented research. In this paper, we present a novel algorithm for recovering sentences and paragraphs from PDF documents, called Sentence Recovery Algorithm or SR algorithm. The algorithm takes plain text extracted from a PDF document as an input, and tends to recover sentences from it. It takes into account cases like misinterpreted end of line, interruption of a sentence by tables or figures, problems occurred by hyphenation and so on. Beside describing and evaluating the algorithm, we present a use case for processing scientific articles originally given in PDF format, implemented in Java programming language.