# Q3a · Coreference and anaphora Subject: Natural Language Processing Exam: TEE Reader: https://deep-learning-study-room.vercel.app/nlp/#tee/papers/legacy-r25/q3a Canonical: https://deep-learning-study-room.vercel.app/read/nlp/tee/papers/legacy-r25--q3a/ Previous examination · complete worked answers **Question. Explain coreference and anaphoric reference with examples.** [5 marks] ### Answer **Pragmatic analysis** interprets an utterance using its situation and the speaker’s intended meaning. **Discourse analysis** studies how utterances connect across a text or conversation. Syntax and literal word meanings alone cannot settle every interpretation. | Text | Literal content | Contextual interpretation | | --- | --- | --- | | “Can you close the window?” | A question about ability. | Usually a polite request. | | “Meera bought a laptop. It was expensive.” | Two sentences. | “It” connects the second sentence to the laptop. | | “Meet me here tomorrow.” | An instruction. | Me, here and tomorrow depend on speaker, place and date. | ### Reference, mention and antecedent A **referring expression** points to an entity; a **mention** is its occurrence in the text. Its **referent** is the entity being discussed. An **antecedent** is a preceding expression used to interpret a later referring expression. Reference resolution identifies the intended referent. Coreference resolution groups mentions that refer to the same entity. “Meera”name mention → Person entitysame referent → “she” / “the engineer”other mentions | Concept | Definition | Example | | --- | --- | --- | | Anaphora | Reference back to something introduced earlier. | “Riya arrived. She sat down.” She → Riya. | | Cataphora | Reference forward to a later expression. | “Before she spoke, Riya checked the microphone.” she → Riya. | | Exophora | Reference to the situation outside the text. | “Put it there”, said while pointing. | | Coreference | Two or more mentions refer to the same entity. | “Dr Rao”, “the lecturer”, “she”. | | Pronoun resolution | Find the referent of a pronoun. | Resolve “it” in “The laptop stopped because it overheated.” | Coreference is broader than pronoun resolution: repeated names and descriptions also form a chain. Anaphora describes direction/dependence; coreference describes identity. In “I bought a car. The engine is noisy”, engine is related to the car but is not the same entity. **Yaad rakho:** Reference = kiski baat? Coreference = alag mentions, same entity. Pronoun resolution = he/she/it kis se linked? ### Cohesion, coherence and discourse markers **Cohesion** is the explicit linguistic linking of a text through reference, repeated or related words, conjunctions and other devices. In “Rita bought a book. She read it”, she and it connect the second sentence to Rita and the book. **Coherence** is the conceptual unity that makes a discourse meaningful. “The road flooded, so the match was cancelled” presents a plausible cause and consequence. A reader relates the propositions using context and knowledge. **Discourse markers** signal relationships or organize speech: however signals contrast; therefore signals a result; first and next signal sequence; for example introduces an illustration. These concepts differ: “I like apples. Therefore the moon is square” has a linking word but no sensible inference. A connector alone does not guarantee coherence. **Yaad rakho:** Cohesion = words se link; coherence = meaning se link; marker = relation ka signal. ### A practical resolution procedure First detect the pronoun and candidate noun phrases. Eliminate candidates inconsistent with person, number, grammatical binding or relevant semantic constraints. Rank the surviving candidates using syntactic prominence, recency and discourse context. Preserve ambiguity if the available evidence does not decide. | Approach | How it works | Strength | Limitation | | --- | --- | --- | --- | | Rule based / syntactic | Use parse trees, agreement and explicit search order; Hobbs is a classic example. | Can explain each decision without labelled training data. | Parsing errors and world knowledge gaps cause errors. | | Salience based | Score candidates using recency, subjecthood and other discourse features; select the strongest compatible candidate. | Captures the tendency to refer again to prominent entities. | Feature weights and competing candidates can mislead. | | Supervised statistical | Learn candidate/pronoun compatibility from labelled examples. | Combines many features from data. | Needs representative annotated examples. | | Neural / contextual | Encode the surrounding text and score mention pairs or antecedents. | Can learn contextual patterns and long-range dependencies. | Needs data/compute and can still make confident mistakes. | ### Worked analysis 1 · number and semantics Resolve “they” in: “Riya put the books on the shelf because they were heavy.” **Given** Candidates: Riya (singular person), books (plural objects), shelf (singular object); pronoun they is plural here. **To find** The antecedent and a justified resolution procedure. ### Formula and why it applies Use number agreement first, then semantic compatibility. There is no multiplication formula in this linguistic task. ### Solution #### Step 1. List candidates Riya, the books, the shelf. #### Step 2. Apply number agreement Riya and shelf are singular. Books is plural, matching they. #### Step 3. Check meaning Books can be heavy; the causal explanation fits carrying/placing books. “They” refers to “the books”. ### Worked analysis 2 · a complete coreference chain Identify the coreference chain in: “Dr Sen entered. The surgeon greeted Ravi. She opened her notebook.” **Given** Mentions: Dr Sen, the surgeon, Ravi, she, her, her notebook. Assume the surgeon is Dr Sen and she/her refers to that surgeon. **To find** The person chain, and a mention that must not be placed in it. ### Formula and why it applies Group expressions by identity of referent; a possessive expression and the owned object are different entities. ### Solution #### Step 1. Link the name and description Dr Sen and the surgeon denote the same person under the given context. #### Step 2. Link the pronouns She and her refer to the surgeon. #### Step 3. Keep the notebook separate “Her notebook” is an object owned by the person; it is not the person herself. Person chain: {Dr Sen, the surgeon, She, her}. “Her notebook” is a separate object mention. ### Worked analysis 3 · honest ambiguity Discuss the pronoun in: “Asha called Nisha after she finished work.” **Given** Both named candidates are singular; the sentence gives no further context. **To find** Whether one referent is logically guaranteed. ### Formula and why it applies Agreement filters incompatible candidates but cannot always select between equally compatible candidates. ### Solution #### Step 1. Check agreement Both Asha and Nisha are compatible with she. #### Step 2. Check the event Either person could have finished work. #### Step 3. State the limitation A heuristic may prefer a candidate, but grammar and this sentence alone do not prove the intended referent. Ambiguous without further context. State any heuristic and parse assumption before giving its preferred candidate.