Graeme Hirst

AAAI Conference 2019 Conference Paper

Enriching Word Embeddings with a Regressor Instead of Labeled Corpora

• Mohamed Abdalla
• Magnus Sahlgren
• Graeme Hirst

We propose a novel method for enriching word-embeddings without the need of a labeled corpus. Instead, we show that relying on a regressor – trained with a small lexicon to predict pseudo-labels – significantly improves performance over current techniques that rely on human-derived sentence-level labels for an entire corpora. Our approach enables enrichment for corpora that have no labels (such as Wikipedia). Exploring the utility of this general approach in both sentiment and non-sentiment-focused tasks, we show how enriching embeddings, for both Twitter and Wikipedia-based embeddings, provide notable improvements in performance for: binary sentiment classification, SemEval Tasks, embedding analogy task, and, document classification. Importantly, our approach is notably better and more generalizable than other state-of-the-art approaches for enriching both labeled and unlabeled corpora.

ECAI Conference 1996 Conference Paper

A Formal and Computational Characterization of Pragmatic Infelicities

• Daniel Marcu
• Graeme Hirst

AIJ Journal 1991 Journal Article

Existence assumptions in knowledge representation

• Graeme Hirst

If knowledge representation formalisms are to be suitable for semantic interpretation of natural language, they must be more adept with representations of existence and nonexistence than they presently are. Quantifiers must sometimes scope over nonexistent entities. I review the philosophical background, including Anselm and Kant, and exhibit some ontological problems that natural language sentences pose for knowledge representation. The paraphrase methods of Russell and Quine are unable to deal with many of the problems. Unfortunately, the shortcomings of the Russell-Quine ontology are reflected in most current knowledge representation formalisms in AI. Several alternatives are considered, including some intensional formalisms and the work of Hobbs, but all have problems. Free logics and possible worlds don't help either. But useful insights are found in the Meinongian theory of Parsons, in which a distinction between nuclear and extranuclear kinds of predicates is made and used to define a universe over which quantification scopes. If this is combined with a naive ontology, with about eight distinct kinds of existence, a better approach to the representation of nonexistence can be developed within Hobbs' basic formalism.

AIJ Journal 1988 Journal Article

Semantic interpretation and ambiguity

• Graeme Hirst

A new approach to semantic interpretation in natural language understanding is described, together with mechanisms for both lexical and structural disambiguation that work in concert with the semantic interpreter. ABSITY, the system described, is a Montague-inspired semantic interpreter. Like Montague formalisms, its semantics is compositional by design and is strongly typed, with semantic rules in one-to-one correspondence with the meaning-affecting rules of a Marcus parser. The Montague semantic objects—functors and truth conditions—are replaced with elements of the frame language FRAIL. ABSITY's partial results are always well-formed FRAIL objects. A semantic interpreter must be able to provide feedback to the parser to help it handle structural ambiguities. In ABSITY, this is done by the “Semantic Enquiry Desk, ” a process that answers the parser's questions on semantic preferences. Disambiguation of word senses and of case slots is done by a set of procedures, one per word or slot, each of which determines the word or slot's correct sense, in cooperation with the other procedures. It is from the fact that partial results are always well-formed semantic objects that the system gains much of its power. This, in turn, comes from the strict correspondence between syntax and semantics in ABSITY. The result is a foundation for semantic interpretation superior to previous approaches.

AAAI Conference 1984 Conference Paper

A Semantic Process for Syntactic Disambiguation

• Graeme Hirst

Structural ambiguity in a sentence cannot be resolved without semantic help. We present a process for structural disambiguation that uses verb expectations, presupposition satisfaction, and plausibility, and an algorithm for making the final choice when these cues give conflicting information. The process, called the Semantic Enquiry Desk, is part of a semantic interpreter that makes sure all its partial results are well-formed semantic objects; it is from this that it gains much of its power.

AAAI Conference 1982 Conference Paper

Word Sense and Case Slot Disambiguation

• Graeme Hirst

The tasks of disambiguating words and determining case are similar and can usefully be combined. We present two cooperating mechanisms that each work on both tasks: MARKER PASSING finds connections between concepts in a system of frames, and POLAROID WORDS provide a protocol for negotiation between ambiguous words and cases. Examples of each in action are given. The cooperating mechanisms allow Iinguistic and world knowledge to be unified, frequently eliminate the need to use inference in disambiguation, and provide a usefully constrained model of disambiguation.