Anaphora

The basics

Keywords

CohesionAnaphoraAnaphorAntecedentAnaphora resolutionCoreferenceCoreferentialPronominal anaphoraLexical NP anaphoraIntrasentential and intersententialLocation of the antecedentsCataphoraAnaphora and deixis

Outline of the lecture

Basic notions and terminologyCoreferenceVarieties of anaphora according to the form of the anaphor Types of according to the locations of the anaphor and the antecedent Indirect anaphora Location of the antecedentAnaphora and cataphora

Basic notions and terminology (1)

Cohesion is a phenomenon accounting for the observation (and assumption) that what people try to communicate in spoken or written form under ‘normal circumstances’ is a coherent whole, rather than a collection of isolated or unrelated sentences, phrases or words Sipping the last of the bitter cordial, the businessman was presented with the cheque. A look of incredulity crept over his face.Sipping the last of the bitter cordial, the businessman was presented with the cheque. A look of incredulity crept over her face.Sipping the last of the bitter cordial, the businessman was presented with the cheque. This lecture is about anaphora.

Basic notions and terminology (2)

Anaphora (Haliday & Hasan 76): cohesion which points back to some previous itemPointing back, NOT referring! Anaphor: the "pointing back" word Antecedent: the entity to which it refers or for which it stands  Anaphora resolution: the process of determining the antecedent of an anaphor

Basic notions and terminology (3)

Coreference: the act of picking out the same referent in the real world.

Anaphors and antecedents are said to be coreferential if they have the same referent in the real world

Example

Sophia Loren says she will always be grateful to Bono. The actress revealed that the U2 singer helped her calm down when she became scared by a thunderstorm while travelling on a plane.Coreferential chains: {Sophia Loren, she, the actress, her, she}, {Bono, the U2 singer}, {a thunderstorm}, {a plane}

Coreference and anaphora

Not all types of anaphora involve coreference!Identity-of-sense anaphora: The man who gave his paycheck to his wife was wiser that the man who gave it to his mistress

Verb anaphora: Stephanie balked, as did Mike

Bound anaphora: Every man has his own agenda

Substitution test to establish coreference

John has his own agenda John has John’s own agenda Every man has his own agenda. Every man has every man’s own agenda. ??

Varieties of anaphora according to

the form of the anaphor

Nominal anaphora arises when a referring expression (pronoun, definite noun phrase or proper name), has a non-pronominal noun phrase as its antecedent. Nominal anaphora: most important and frequently occurring class

of anaphora researched and covered most extensively, and

best understood in the Computational Linguistics literature.

Varieties of anaphora according to the form of the anaphor (2)

Pronominal anaphora: the most widespread type of anaphoraPersonal pronouns: John had to go to a meeting so he decided to have a shavePossessive pronouns: John grabbed his old razorReflexive pronouns...but unfortunately cut himself during the shaveDemonstrative pronouns: This delayed him further... John picked the electric razor. That was not working eitherRelative pronouns: John picked the electric razor which was not working either).

Varieties of anaphora according to the form of the anaphor (3)

Lexical noun phrase anaphora: realised syntactically as definite noun phrases, also called definite descriptions, and proper names.Roy Keane has warned Manchester United he may snub their pay deal. United's skipper is even hinting that unless the future Old Trafford Package meets his demands, he could quit the club in June 2000. Irishman Keane, 27, still has 17 months to run on his current £23,000-a-week contract and wants to commit himself to United for life. Alex Ferguson's No. 1 player confirmed: ‘If it's not the contract I want, I won't sign’

Lexical noun phrase anaphors: further examples

Mark went for a drive and got hopelessly lost. That's Mark for you.

Both noses went down to the footprints in the snow. These footprints were very fresh.

Most crucial (and most studied) type of anaphora in NLP

identity-of-reference nominal anaphora: involves coreference by virtue of the anaphor and its antecedent having the same real-world referent

Zero anaphora

Zero anaphors are ‘invisible' anaphors Zero pronominal anaphora occurs when the anaphoric pronoun is omitted but is nevertheless understood Willie paled and pulled the sock up quickly Marta está muy cansada. Ha estado trabajando todo el día.

Anaphoric / non-anaphoric

Are pronouns always anaphoric?Pleonastic it: It is important, It is necessary, It is far away, It is raining….Generic use of pronouns: He that plants thorns must never expect to gather roses.

Are definite descriptions always anaphoric?Generic definite descriptions:No one knows precisely when the wheel was invented

Types of anaphora according to the locations

of the anaphor and the antecedent

intrasentential : anaphor and its antecedent are located in the same sentence.intersentential : antecedent is in a different (preceding) sentence from the anaphorPop superstar Robbie Williams hid his secret heartbreak as he picked up three Brit awards last night. He was stunned to discover that his ex-fiancée, All Saints beauty Nicole Appleton, is dating a New York rapper. Robbie, 25, was distraught after being dumped by the love of his life Nicole at Christmas.

Indirect anaphora (bridging, associative anaphora)

Indirect anaphora: arises when a reference becomes part of the hearer’s or reader’s knowledge indirectly rather than by direct mention:

Although the store had only just opened, the food hall was busy and there were long queues at the tills. When Take That broke up, the critics gave Robbie Williams no chance of success.

Location of the antecedent

Pronominal anaphors: distance between a pronominal anaphor and its antecedent in most cases does not exceed 2-3 sentencesDemonstrative anaphors: longer-distance anaphors than pronounsDefinite descriptions: longer-distanceProper names: even longer-distance anaphors

Cataphora

Cataphora arises when a reference is made to an entity mentioned subsequently in the text.

 She is now as famous as her ex-boyfriend. From the deserts of Kazakhstan to the south seas of Tonga, everyone knows Monica Lewinsky

Anaphora and Deixis

He seems remarkably bright for a child of his age.George is only 4 but can read and write in both English and Bulgarian. He seems remarkably bright for a child of his age.I want you to be here now. Maggie came to England when she was four, and has lived here ever since

Anaphora resolution

Anaphora resolution: the process of determining the antecedent of an anaphor

Identity-of-reference nominal anaphora: preceding lexical noun phrases that are coreferential with the anaphor(s) are regarded as a legitimate antecedent

Sophia Loren says she will always be grateful to Bono. The actress revealed that the U2 singer helped her calm down when she became scared by a thunderstorm while travelling on a plane.

Coreference resolution

Idenification of all coreferential chainsSophia Loren says she will always be grateful to Bono. The actress revealed that the U2 singer helped her calm down when she became scared by a thunderstorm while travelling on a plane.Coreferential chains: {Sophia Loren, she, the actress, her, she}, {Bono, the U2 singer}, {a thunderstorm}, {a plane}