Machine Translation 13: 135–227, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands. 135 An Applied Ontological Semantic Microtheory of Adjective Meaning for Natural Language Processing VICTOR RASKIN Natural Language Processing Laboratory, Purdue University, West Lafayette, IN 47907-1336, USA vraskin@purdue.edu SERGEI NIRENBURG Computing Research Laboratory, New Mexico State University, Las Cruces, NM 88003, USA sergei@crl.nmsu.edu Abstract. This paper is devoted to determining and representing adjectival meaning. The results form a microtheory in the Mikrokosmos project on computational ontological semantics. Mikrokos- mos microtheories cover the meaning of lexical categories in several languages, the ontological model used as metalanguage for language description and syntax–semantics mapping as well as the actual process of text analysis and generation. This paper presents a critical analysis of the body of knowledge on adjectives amassed to date in linguistics and presents a detailed, practically tested methodology and heuristics for the acquisition of adjectival lexical entries for computational applications. The work is based on the set of over 6,000 English and about 1,500 Spanish adjectives obtained from task-oriented corpora. Key words: ontological semantics, adjectives, computational lexicography, corpora 1. Introduction The goal of this paper is to determine how much information about adjectival meaning should be included in a computational lexicon for broad-coverage ma- chine translation (MT). We concentrate on adjectival meaning proper and not on how lexical entries for adjectives are used in producing computational semantic analyses. The latter issue will be part of a report about semantic analysis in the Mikrokosmos project, including the semantic analysis of adjectival modification as one of the many manifestations of the phenomenon of modification in language (see also Raskin and Nirenburg, 1996a,b). 1 The practical objective of the study has been to develop a method for describing the semantics of adjectives in a corpus of Spanish and English journalistic texts as part of a larger effort to develop a computational method for determining and representing the meaning of natural language texts. Some fundamental premises