--- title: "Factors in anaphora resolution — Mitkov 1997" description: "Mitkov asks whether good anaphora resolution depends only on picking reliable factors, or also on how those factors are applied." authors: ["Ruslan Mitkov"] year: 1997 venue: "Operational Factors in Practical, Robust Anaphora Resolution for Unrestricted Texts" source: "https://aclanthology.org/W97-1303/" licence: "CC BY-NC-SA 3.0 (ACL Anthology, before 2016)" licence_url: "https://creativecommons.org/licenses/by-nc-sa/3.0/" summary_licence: "Elamur Cosmic License" canonical: "https://research.elamur.ai/free/papers/mitkov-1997-factors-anaphora-resolution-they-are/" --- [Elamur Research](https://md.research.elamur.ai/) · [this page in HTML](https://research.elamur.ai/free/papers/mitkov-1997-factors-anaphora-resolution-they-are/) [home](https://md.research.elamur.ai/) / [papers](https://md.research.elamur.ai/free/papers/) / [1997](https://md.research.elamur.ai/free/papers/1997/) / Factors in anaphora resolution: they are not the only things that matter. A case study based on two different approaches # Factors in anaphora resolution: they are not the only things that matter. A case study based on two different approaches **Authors:** [Ruslan Mitkov](https://md.research.elamur.ai/free/authors/ruslan-mitkov/) · **Year:** 1997 · **Venue:** Operational Factors in Practical, Robust Anaphora Resolution for Unrestricted Texts · **Licence:** [CC BY-NC-SA 3.0 (ACL Anthology, before 2016)](https://creativecommons.org/licenses/by-nc-sa/3.0/) **Links:** [Publisher's page](https://aclanthology.org/W97-1303/) · [PDF](https://aclanthology.org/W97-1303.pdf) · [OpenAlex](https://openalex.org/W7096180988) **Citations:** 0 citations (openalex-snapshot · 2026-10-14) · [11](#cited-by) in our library, of the 140673 papers whose bibliographies we read ## Summary Mitkov asks whether good anaphora resolution depends only on picking reliable factors, or also on how those factors are applied. He tests this by giving two of his own pronoun resolvers the same core set of factors. These include gender and number agreement, c-command, semantic consistency, syntactic and semantic parallelism, topicalisation, and several empirically motivated preferences such as section heading and object preference signalled by verbs or nouns. The first system, the Integrated Approach (IA), uses constraints to remove impossible candidates and then ranks the rest by preferences, with the strongest weight on the previous clause's center. The second, the Uncertainty Reasoning Approach (URA), never discards candidates. It treats every factor as a weighted preference and accepts or rejects each candidate through certainty-factor arithmetic. The texts come mainly from the computer-science sublanguage, as in the original systems. The study finds that the two strategies perform differently even with identical factors, and that combining them as a two-engine system works best. The broader lesson is that system builders should choose the resolution strategy as carefully as the factors. ## Key points - **Integrated Approach (IA).** It is built from rule-based syntactic, semantic, domain, discourse and heuristic modules, plus a filter for non-anaphoric "it". Its discourse module estimates the center of each sentence, including the first, using an inference engine based on Bayes' formula. - **Uncertainty Reasoning Approach (URA).** It uses a modified version of van Melle's formula (from Buchanan & Shortliffe 84) to update a candidate's certainty factor until it crosses an acceptance threshold or falls below a rejection limit. Candidates are tested starting from the noun phrase closest to the anaphor. In the paper's worked example, a candidate at 0.5 that meets a symptom worth 0.45 rises to 0.725. - **Main finding.** The paper's own results report that combining IA and URA into a two-engine strategy outperformed either system alone. This partly agrees with Carter's earlier comparison of SPAR and the SRI Core Language Engine. - **Factor dependence.** The two object-preference factors (indicated by verbs and by nouns) are mutually dependent. Mitkov partly compensates by giving the noun-based factor a lower value, but argues that proper modelling requires dependence data from large annotated corpora. - **Order of application.** Applying preferences in descending versus ascending order of value made no essential difference to the outcome, but the ascending order made the search longer. Mitkov leans towards preference-only designs, because strict agreement constraints can wrongly exclude correct antecedents, for example collective nouns referred to by "they". *Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.* Fields: [Linguistics & languages](https://md.research.elamur.ai/free/shelves/linguistics/) Topics: [Coreference resolution](https://md.research.elamur.ai/free/topics/coreference-resolution/) ## Cited by Cited by 11 papers of our library cite it (of the 140673 whose bibliographies we read); 6 of them have a page here, 5 not yet. - [Bootstrapping Path-Based Pronoun Resolution](https://md.research.elamur.ai/free/papers/bergsma-2006-bootstrapping-path-based-pronoun-resolution/) - [A Generic Anaphora Resolution Engine for Indian Languages](https://md.research.elamur.ai/free/papers/devi-2014-generic-anaphora-resolution-engine-indian/) - [A Statistical Approach to Anaphora Resolution](https://md.research.elamur.ai/free/papers/ge-1998-statistical-approach-anaphora-resolution/) - [Exploiting Syntactic Patterns as Clues in Zero-Anaphora Resolution](https://md.research.elamur.ai/free/papers/iida-2006-exploiting-syntactic-patterns-as-clues/) - [Improving Machine Learning Approaches to Coreference Resolution](https://md.research.elamur.ai/free/papers/ng-2002-improving-machine-learning-approaches-coreference/) - [A Machine Learning Approach to Coreference Resolution of Noun Phrases](https://md.research.elamur.ai/free/papers/soon-2001-machine-learning-approach-coreference-resolution/) ## Cite The paper itself, not this page. BibTeX from the library's record of the work. ```bibtex @inproceedings{mitkov1997factors, title = {{Factors in anaphora resolution: they are not the only things that matter. A case study based on two different approaches}}, author = {Mitkov, Ruslan}, booktitle = {Operational Factors in Practical, Robust Anaphora Resolution for Unrestricted Texts}, year = {1997}, url = {https://aclanthology.org/W97-1303/} } ``` - [← previous Event coreference for information extraction](https://md.research.elamur.ai/free/papers/humphreys-1997-event-coreference-information-extraction/) - [next → GermaNet - a Lexical-Semantic Net for German](https://md.research.elamur.ai/free/papers/hamp-1997-germanet-lexical-semantic-net-german/) - [↑ back to papers of 1997](https://md.research.elamur.ai/free/papers/1997/) ## References 14 references, 4 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet. 1. H. Alshawi - Resolving quasi logical forms. Computational Linguistics, 16:3, 1990 [find](https://scholar.google.com/scholar?q=H%2E+Alshawi+%2D+Resolving+quasi+logical+forms%2E+Computational+Linguistics%2C+16%3A3%2C+1990) 2. B. Buchanan, FEd. Shortliffe Rule-based expert systems. Addison-Wesley, 1984 [find](https://scholar.google.com/scholar?q=B%2E+Buchanan%2C+FEd%2E+Shortliffe+Rule%2Dbased+expert+systems%2E+Addison%2DWesley%2C+1984) 3. J. Carbonell, R. Brown - - Anaphora resolution: a multi-strategy approach. Proceedings of the 12. International Conference on Computational Linguistics COLING'88, Budapest, August, 1988 [find](https://scholar.google.com/scholar?q=J%2E+Carbonell%2C+R%2E+Brown+%2D+%2D+Anaphora+resolution%3A+a+multi%2Dstrategy+approach%2E+Proceedings+of+the+12%2E+International+Conference+on+Computational+Linguistics+COLING%2788%2C+Budapest%2C+August%2C+1988) [our card](https://md.research.elamur.ai/free/papers/carbonell-1988-anaphora-resolution-multi-strategy-approach/) 4. D. Carter - Interpreting anaphora in natural language texts. Chichester: Ellis Horwood, 1987 [find](https://scholar.google.com/scholar?q=D%2E+Carter+%2D+Interpreting+anaphora+in+natural+language+texts%2E+Chichester%3A+Ellis+Horwood%2C+1987) 5. David M. Carter - Control issues in anaphor resolution. Journal of Semantics, 7, 1990 [find](https://scholar.google.com/scholar?q=David+M%2E+Carter+%2D+Control+issues+in+anaphor+resolution%2E+Journal+of+Semantics%2C+7%2C+1990) 6. I. Dagan - Multilingual statistical approaches for natural language disambiguation (in Hebrew). PhD dissertation. Technion-Israel Institute of Technology, Haifa [find](https://scholar.google.com/scholar?q=I%2E+Dagan+%2D+Multilingual+statistical+approaches+for+natural+language+disambiguation+%28in+Hebrew%29%2E+PhD+dissertation%2E+Technion%2DIsrael+Institute+of+Technology%2C+Haifa) 7. Ido Dagan, John Justeson, Shalom Lappin, Hergert Leass and Amnon Ribak - Syntax and lexical statistics in anaphora resolution. Applied Artificial Intelligence, 9, 1995 [find](https://scholar.google.com/scholar?q=Ido+Dagan%2C+John+Justeson%2C+Shalom+Lappin%2C+Hergert+Leass+and+Amnon+Ribak+%2D+Syntax+and+lexical+statistics+in+anaphora+resolution%2E+Applied+Artificial+Intelligence%2C+9%2C+1995) 8. Sh. Lappin, H. Leass - An algorithm for pronominal anaphora resolution. Computational Linguistics, 20(4), 1994 [find](https://scholar.google.com/scholar?q=Sh%2E+Lappin%2C+H%2E+Leass+%2D+An+algorithm+for+pronominal+anaphora+resolution%2E+Computational+Linguistics%2C+20%284%29%2C+1994) [our card](https://md.research.elamur.ai/free/papers/lappin-1994-algorithm-pronominal-anaphora-resolution/) 9. Mitkov R. - An integrated model for anaphora resolution. Proceedings of the 15th International Conference on Computational Linguistics COLING'94, Kyoto, Japan, 5-9 August 1994 [find](https://scholar.google.com/scholar?q=Mitkov+R%2E+%2D+An+integrated+model+for+anaphora+resolution%2E+Proceedings+of+the+15th+International+Conference+on+Computational+Linguistics+COLING%2794%2C+Kyoto%2C+Japan%2C+5%2D9+August+1994) [our card](https://md.research.elamur.ai/free/papers/mitkov-1994-integrated-model-anaphora-resolution/) 10. Mitkov R. - A new approach for tracking center. In Proceedings of the International Conference "New Methods in Language Processing", UMIST, Manchester, UK, 13-16 September 1994 [find](https://scholar.google.com/scholar?q=Mitkov+R%2E+%2D+A+new+approach+for+tracking+center%2E+In+Proceedings+of+the+International+Conference+%22New+Methods+in+Language+Processing%22%2C+UMIST%2C+Manchester%2C+UK%2C+13%2D16+September+1994) 11. R. Mitkov - An uncertainy reasoning approach to anaphora resolution. 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