Specialized Information Extraction: Automatic Chemical Reaction Coding From English Descriptions

SPECLkLIZEI) [NFOKMATION EXTRACTION: AUTOMATIC CHEMICAL RFACTION CODING FROM ENGLIS}t DF.SCR£?'r[ONS Larr,, H. Reeker* Elena M. 7.~ lura** and Paul E. Blower Chemical Abstracts Service 2540 Olentangy River Road P.O. Box 3012 Columbus, Ohio 43210 ABSTRACT In an age of increased attention to the problems of database o rganlzat ion, retrieval problems and query languages, one of the major economic problems of many potential databases remains the entry of the original information into the database. Specialized information extraction (SIE) systems are therefore of potential impor- tance in the entry of information that is already available in certain restricted types of natural language text. This paper contains a discussion of the problems of enElneering such systems and a description of a particular SIE system, designed to extract information regarding chemical reac- tions from experimental sections of papers in the chemical literature and to produce a data struc- ture containing the relevant information. I. INTRODUCTION A. Overview of the Paper In an age of increased attention to the problems of database organization retrieval problems and query languages, one of the major economic problems of many potential databases remains the entry of the original information into the database. A large amount of such information is currently available in natural language text, and some of that text is of a higi~ly stylized nature, with a restricted semantic domain. It is the task of specialized information extract ion (SIE) systems to obtain information automatically from such texts and place it in the database. As with any system, it is desirable to minimize errors and human intervention, bur a total absence of either is not necessary for the system to be economically viabl~. * Current address: Department of Computer Science, Tulane University, New OrleanS, Louisiana 70118, ** Current address: P.O. Box 3554, Gaithersburg, Maryland 20278. 109 In ~his paper, we will first discuss some general characterlstics of SIE systems, then describe the development of an experimental system to assist in the coastructlon of a database of chemical reaction information. Many Journals, such as the Journal of Or~anlc Chemistry, have separate experimental sections, in which ~he procedures for preparing chemical compounds are described. It is desired to extract certain information about these reactions and place it in the database. A reaction information form (RIF) was developed in another project to contain the desired information. The purpose of the system is tO eliminate the necessity in a majority of cases, for a trained reader to read the text and enter the P.IF information into the machine. B. Some Terminology In the discussion below, we shall use the term ~rammmr to mean a system conslstin 8 of a lexicon s a s~ntax, a meanin~ representation lan- guage, and a z~ntlc mapping. The lexicon consists of the ~st of words in the language and one or more grammatical categories for each word. The syntax specifies the structure of sentences in the language in terms of the grammar ical categories. Morphological procedures may specify a "syntax" within classes of words and thereby …

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