ZERO PRONOUN RESOLUTION IN JAPANESE Jeffrey Shu Ling 575 Discourse and Dialogue

Review of Zero Pronouns  (Pro)nouns often dropped if pragmatically/semantically inferable from context  General preference for names/nouns rather than pronouns in polite/formal speech (except 1 st person and demonstrative pronouns)  Grammatical markers removed with nouns  Pronominal referent may or may not appear in discourse prior to appearance of zero pronoun

Overview of Objectives  Find general syntactic rules that can be used to identify the presence of zero pronouns  Find syntactic/semantic/pragmatic clues to identify referents for ZPs, or determine appropriate pronoun/noun insertion if not explicitly found in textual context  Determine priority in case of conflict

Syntactic Identification of Zero Pronouns  Determining presence of zero pronoun fairly straightforward for subject/topic, objects  Determine syntactic argument structure of verb  Identify if noun exists to fill arguments (simple task with grammatical markers) Sometimes grammatical markers not used in casual speech  Not so straightforward for other nouns (e.g. locatives)  Might not be important if unstated (e.g. “I’ll go to the store” vs. “I’ll go”). Usually has precedent.

Findings: Some Generalizations from Semantics/Syntax  In consecutive statements with ZPs, the topic/subject is often the same  Many verbs have a semantic preference for certain types of nouns (e.g. animate vs. inanimate) which can narrow possibilities  Imperatives are always 2 nd person (unless speaker is talking to him/herself)  Rarely have a subject/topic

Findings: Conversations  1P by far most commonly used pronoun  If ZP in statement is 1P, usually has an explicit precedent  If 2P, it may or may not have an explicit precedent  Question/answer format generalizations  Subject/topic of question usually 2/3P If1P, often directly stated  Subject of answer almost always opposite pronoun of question (2/3P vs. 1P), same referent (i.e. same person)  3P both simplest and potentially most complicated  3P personal pronouns (e.g. he/she) very rarely used  If 3P ZP, almost always preceded by explicit reference to name/noun  Gender indeterminate (possible problem for MT)

Findings: Domain Specific  Formal situations usually dictate specific conventions to be followed  Representatives almost never use 1P singular or 3P personal pronouns  2P ZPs can be inferred from domain context (a corporate statement would probably be addressing its customers or investors)

Findings: Domain Specific  Reference articles (e.g. Wikipedia)  While ZPs commonly are used, the antecedent is usually found no more than a few sentences prior  ZPs in consecutive sentences usually have same referent  If no clear antecedent can be found, subject of article is often a reasonable assumption  1 st and 2 nd person virtually non-existent, can be safely eliminated as possibilities Exceptions: reader-addressed texts (e.g. reference guides)  News articles similar conventions

Findings: Domain Specific  Visual media (e.g. comics, TV, etc.)  Most problematic  Referent very often in visual context with no textual context  Heavy reliance on visuals results in not only (pro)noun dropping, but “anything” dropping (including verbs), losing syntactic information  Quite possibly impossible to resolve without human intervention  Purely textual works (e.g. novels) usually have enough information

Priority  Domain has highest priority in all situations  Rules for separate domains largely mutually exclusive  Failure to determine reasonable pronouns as determined to be can lead to misinformation  Japanese particularly sensitive to social context Generic pronoun insertion may be highly inappropriate  Simple domain information can be extremely valuable  Unless ruled out by domain, general conversation rules may be applicable to many different media

Priority  Pragmatics/semantics > syntax  Ex: Question/answer conventions are of greater relevance than assumption that the subject of the previous sentence is the same as the subject of the current sentence  Ex: The semantics of verbs to prefer certain types of nouns is of greater relevance than the fact that a ZP is a particular grammatical role (e.g. naïve assumption that direct objects tend to be inanimate)

An Idea  Instead of inserting “best guess” pronouns, provide a selection of best candidates in text for user to disambiguate  In current MT systems that insert generic pronouns, users have to “interpret” (guess) what is really meant anyway  Insertion of pronouns is never 100% certain  Some media (visual) require human intervention  Insertion of pronouns/nouns can lead to misinformation, faux pas, and sense of unreliability of system  It is much faster to pick out of a set of provided candidates rather than guess whether the pronoun is right or wrong, and go back to try to figure out what is going on