{ "paper_id": "E95-1029", "header": { "generated_with": "S2ORC 1.0.0", "date_generated": "2023-01-19T10:31:33.366784Z" }, "title": "Specifying a shallow grammatical representation for parsing purposes", "authors": [ { "first": "Atro", "middle": [], "last": "Voutilainen", "suffix": "", "affiliation": { "laboratory": "Research Unit for Multilingual Language Technology", "institution": "University of Helsinki Finland At ro.Voutilainen", "location": { "postBox": "P.O. Box 4", "postCode": "FIN-00014", "country": "Timo. J" } }, "email": "" }, { "first": "Timo", "middle": [], "last": "J~irvinen", "suffix": "", "affiliation": { "laboratory": "Research Unit for Multilingual Language Technology", "institution": "University of Helsinki Finland At ro.Voutilainen", "location": { "postBox": "P.O. Box 4", "postCode": "FIN-00014", "country": "Timo. J" } }, "email": "" } ], "year": "", "venue": null, "identifiers": {}, "abstract": "Is it possible to specify a grammatical representation (descriptors and their application guidelines) to such a degree that it can be consistently applied by different grammarians e.g. for producing a benchmark corpus for p.arser evaluation? Arguments for and against have been given, but very little empirical evidence. In this article we report on a double-blind experiment with a surfaceoriented morphosyntactic grammatical representation used in a large-scale English parser. We argue that a consistently applicable representation for morphology and also shallow syntax can be specified. A grammatical representation with a near-100% coverage of running text can be specified with a reasonable effort, especially if the representation is based on structural distinctions (i.e. it is structurally resolvable).", "pdf_parse": { "paper_id": "E95-1029", "_pdf_hash": "", "abstract": [ { "text": "Is it possible to specify a grammatical representation (descriptors and their application guidelines) to such a degree that it can be consistently applied by different grammarians e.g. for producing a benchmark corpus for p.arser evaluation? Arguments for and against have been given, but very little empirical evidence. In this article we report on a double-blind experiment with a surfaceoriented morphosyntactic grammatical representation used in a large-scale English parser. We argue that a consistently applicable representation for morphology and also shallow syntax can be specified. A grammatical representation with a near-100% coverage of running text can be specified with a reasonable effort, especially if the representation is based on structural distinctions (i.e. it is structurally resolvable).", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Abstract", "sec_num": null } ], "body_text": [ { "text": "The central task of a parser is to assign grammatical descriptions onto input sentences. Evaluating a parser's output (as well as designing a computational lexicon and grammar) presupposes a predefined, parser-independent specification of the grammatical representation.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "Perhaps surprisingly, the possibility of specifying a workable grammatical representation is a matter of controversy, even at lower levels of analysis, e.g. morphology (incl. parts of speech).", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "Consider the following setting (the double-blind experiment). Two linguists trained to apply a tag set to running text according to application guidelines (a \"style sheet\") are to analyse a given data individually. The results are then automatically compared, and the differences are jointly examined by these linguists to see whether the differences are due to inattention, or whether they are intentional (i.e. there is a genuine difference in analysis). -How many percentage points of all words in running text are retain a different analysis after the differences due to inattention have been omitted? The higher this percentage, the more susceptible seems the possibility of specifying a workable grammatical representation.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "According to a pessimistic view (e.g. Church 1992), the part of speech of several percentage points of words in running text is impossible to agree on by different judges, even after negotiations. A more optimistic view can be found in (Leech and Eyes 1993, p. 39; Marcus et al. 1993, p. 328) ; they argue that a near-100% interjudge agreement is possible, provided the part-of-speech annotation is done carefully by experts. Unfortunately, they give very little empirical evidence for their position e.g. in terms of double-blind experiments.", "cite_spans": [ { "start": 236, "end": 264, "text": "(Leech and Eyes 1993, p. 39;", "ref_id": null }, { "start": 265, "end": 292, "text": "Marcus et al. 1993, p. 328)", "ref_id": null } ], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "Supposing defining these lower levels of grammatical representation is so problematic, the more distinctive levels should be even more difficult. If specifying the task of the parser -what the parser is supposed to do -turns out to be so problematic, one could even question the rationality of natural language parser design as a whole. In other words, the controversy regarding the specifiability of a grammatical representation is a fundamental issue.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "In this article we report on a double-blind experiment with a surface-oriented morphosyntactic grammatical representation used by a large-scale English parser. We show that defining a grammatical representation is possible, even relatively straightforward. We present results from part-ofspeech annotation and shallow syntactic analysis. Our three main findings are: 1. A practically 100% interjudge agreement can be reached at the level of morphological (incl. part-of-speech) analysis provided that (i) the grammatical representation is based on structural distinctions and (ii) the individual descriptive practices of the most frequent 'problem cases' are properly documented.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "2. A shallow dependency-oriented functional syntax can be defined, very much like a morphological representation. The only substan-tial difference seems to be that somewhat more effort for documenting the individual solution is needed at the level of syntax.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "3. A grammatical representation (morphosyntactic descriptors and their application guidelines) can be specified with a reasonable effort. In addition to general descriptive principles, only a few dozen construction-specific entries seem necessary for reaching a high coverage of running text.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "In short: In this paper we give empirical evidence for the possibility of specifying a grammatical representation in enough detail to make it (almost) consistently applicable. What we are less specific about here is the exact formal properties that make a representation easy to specify; this topic remains open for future investigation.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Introduction", "sec_num": "1" }, { "text": "In the experiment to be reported in Section 3, we employed the grammatical representation that defines the descriptive task of the English Constraint Grammar Parser ENGCG (Karlsson et al. (eds.) 1995). 1", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Grammatical representation in English Constraint Grammar", "sec_num": "2" }, { "text": "The morpholexical component in ENGCG employs 139 morphological tags for part of speech, inflection, derivation and certain syntactic properties (e.g. verb classification). Each morphological analysis usually consists of several tags, and many words get several analyses as alternatives.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "The following analysis of the sentence That round table might collapse is a rather extreme example:", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "\"<*that>\" \"that\"", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "\"that\"", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "\"that\" \"that\" \"that\" \"\" \"round\" \"round\" \"round\" \"round\" \"round\" \"round\" \"round\" \"round\" \"\" \"table\" \"table\"", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "<*> <**CLB> CS <*> DET CENTRAL DEM SG <*> ADV <*> PRON DEM SG <*> <**CLB> PRON SG/PL V SUBJUNCTIVE VFIN V IMP VFIN V INF V PRES -SG3 VFIN PREP N NOM SG A ABS ADV N NOM SG V SUBJUNCTIVE VFIN", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "aA list of the ENGCG tags can be retrieved via e-mail by sending an empty mail message to engcginfo@ling.helsinki.fi. The returned document will also tell how to analyse own samples using the ENGCG server. \"table\" V IMP VFIN \"table\" V INF \"table\" V PRES -SG3 VFIN \"\" \"might\" N NOM SG \"might\" V AUXMOD VFIN \"\"", "cite_spans": [], "ref_spans": [ { "start": 206, "end": 294, "text": "\"table\" V IMP VFIN \"table\" V INF \"table\" V PRES -SG3 VFIN \"\"", "ref_id": null } ], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "\"collapse\" N NOM SG \"collapse\" V SUBJUNCTIVE VFIN \"collapse\" V IMP VFIN \"collapse\"", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": " V INF \"collapse\" V PRES -SG3 VFIN ,,<$.>,,", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "The morphological analyser produces about 180 different tag combinations. To compare the ENGCG morphological description with another well-known tag set, the Brown Corpus tag set: ENGCG is more distinctive in that the part of speech distinction is spelled out in the description of determiner-pronoun, preposition-conjunction, and determiner-adverb-pronoun homographs, as well as uninflected verb forms, which are represented as ambiguous due to the subjunctive, imperative, infinitive and present tense readings. On the other hand, ENGCG does not spell out partof-speech ambiguity in the description of -ing and nonfinite -ed forms, noun-adjective homographs when the core meanings of the adjective and noun readings are similar, nor abbreviations vs. proper vs. common nouns. Generally, the ENGCG morphological tag set avoids the introduction of structurally unjustified distinctions.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Morphology", "sec_num": "2.1" }, { "text": "ENGCG syntax employs 30 dependency-oriented functional tags that indicate the surface-syntactic roles of nominal heads (subject, object, preposition complement, apposition, etc.) and modifiers (premodifiers, postmodifiers). The shallow structure of verb chains is also given -the tag set distinguishes between auxiliaries and main verbs, finite and nonfinite. Also the structure of adverbials as well as prepositional and adjective phrases is given, though some of the attachments of adverbials is left underspecified.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Syntax", "sec_num": "2.2" }, { "text": "Finally, a disambiguated sample analysis of the above sample sentence: \"<*that>\" \"that\" <*> DET CENTRAL DEM SG @DN> \"'\u00b0 \"round\" A ABS @AN> \"
\"", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Syntax", "sec_num": "2.2" }, { "text": "\"table\" N N0M SG @SUBJ \"\" \"might\" V AUXMOD VFIN ~+FAUXV \"\" \"collapse\" V INF @-FMAINV \"<$. >,, Syntactic tags are flanked with the @-sign; 2 morphological tags and the base form are given to the left of the syntactic tags.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Syntax", "sec_num": "2.2" }, { "text": "This section reports on an experiment on partof-speech and syntactic disambiguation by human experts (the authors of this article). Three 2,000word texts were successively used: a software manual, a scientific magazine, and a newspaper.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "The experiment", "sec_num": "3" }, { "text": "The experiment was conducted as follows.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Setting", "sec_num": "3.1" }, { "text": "1. The text was morphologically analysed using the ENGCG morphological analyser. For the analysis of unrecognised words, we used a rule-based heuristic component that assigns morphological analyses, one or more, to each word not represented in the lexicon of the system.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Setting", "sec_num": "3.1" }, { "text": "2. Two experts in the ENGCG grammaticalrepresentation independently marked the correct alternative analyses in the .ambiguous input, using mainly structural, but in some structurally unresolvable cases also higher-level, information. The corpora consisted of continuous text rather than isolated sentences; this made the use of textual knowledge possible in the selection of the correct alternative. In the rare cases where two analyses were regarded as equally legitimate, both could be marked. The judges were encouraged to consult the documentation of the grammatical representation.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Setting", "sec_num": "3.1" }, { "text": "3. These tagged versions were compared to each other using the Unix sdiff program.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Setting", "sec_num": "3.1" }, { "text": "4. The differences were jointly examined by the judges in order to see whether they were due to (i) inattention, (ii) incomplete specification of the grammatical representation or (iii) an undecidable analysis.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Setting", "sec_num": "3.1" }, { "text": "A 'consensus' version of the tagged corpus was prepared. Usually only a unique analysis was given. However, there were three situations where a multiple analysis was accepted:", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "\u2022 When the judges disagree about the correct analysis even after negotiations. In this case, comments were added to distinguish it from the other two types. \u2022 Neutralisation: both analyses were regarded as equivalent. (This often indicates a redundancy in the lexicon.)", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "2,,@DN>, represents determiners; \"@AN>\" represents premodifying adjectives; \"@SUB J\" represents subjects; \"@+FAUXV\" represents finite auxiliaries; and \"@-FMAINV\" represents nonfinite m~in verbs.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "\u2022 Global ambiguity: the sentence was agreed to be globally ambiguous.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "6. Whenever an undefined construction was detected during the joint examination, the grammar definition manual was updated.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "7. The preparation of the syntactic version was the next main step. For each contextually appropriate morphological reading, all syntactic tags were introduced with a mapping program. An example: 3 \"<*that>\" \"that\" <*> DET CENTRAL DEM SG @DN> \"\" \"round\" A ABS @AN> \"
\" \"table\" N NOM SG @NPHR ~SUBJ @OBJ @I-OBJ @PCOMPL-S @PCOMPL-0 @APP @NN> @

\" \"might\" V AUXMOD VFIN @+FAUXV \"\" \"collapse\" V INF @-FMAINV @,, 8. Steps 2-6 were applied to these syntactic ambiguities.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "This procedure was successively applied to the three texts to see how much previous updates of the grammar definition manual decreased the need for further updates and how much the interjudge agreement might increase even after the first mechanical comparison (cf.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "Step 3).", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "5.", "sec_num": null }, { "text": "The results are given in Figure 1 (next page) .", "cite_spans": [], "ref_spans": [ { "start": 25, "end": 45, "text": "Figure 1 (next page)", "ref_id": null } ], "eq_spans": [], "section": "Results", "sec_num": "3.2" }, { "text": "Some comments are in order, first about morphology.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Results", "sec_num": "3.2" }, { "text": "\u2022 The initial consistency rate was constantly above 99%.", "cite_spans": [], "ref_spans": [], "eq_spans": [], "section": "Results", "sec_num": "3.2" }, { "text": "\u2022 After negotiations, the judges agreed about the correct analysis or analyses in all cases. The vast majority of the initial differences were due to inattention, and the remaining few to incomplete specification of the morphological representation. Some representative examples about these jointly examined 3,,@NPHR, represents stray nominal heads; \"@OBJ\" represents objects; \"@I-OBJ\" represents indirect objects; \"@PCOMPL-S\" represents subject complements; \"@PCOMPL-O\" represents object complements; \"@APP\" represents appositions; \"@NN>\" represents premodifying nouns (and nonfinal noun parts in compounds); \"@) keeping ?@-FMAINV / @SUB J)in(@ADVL / @\" represents genitival premoditlers, and \"~