Constraints on Coreference

Number agreement specifies that elements of a composite must follow the rules of syntax with regard the attribute number.

In discourse, number agreement means referring expressions and their referrents must agree in number. This means singular or plural distinction in references when speaking English.

In individual sentence parsing, we have requirements of noun/verb agreement:
Example: *He eat at the finest restaurants.
Example: He eats at the finest restaurants.

In discourse analysis the concern becomes inter-sentence [JM] :
Example: 18.26 John has a new Acura. It is red.
Example: 18.27 John has three new Acuras. They are red.
Example: 18.28 *John has a new Acura. They are red.
Example: 18.29 *John has three new Acuras. It is red.

Person and Case Agreement

Person agreement specifies that elements of a composite match in terms of their use of first, second, and third person [JM]:

Example: 18.30 You and I have Acuras. We love them.
Example: 18.31 John and Mary have Acuras. They love them.
Example: 18.32 *John and Mary have Acuras. We love them.¹
Example: 18.33 *You and I have Acuras. They love them.
¹ This illustrates an ambiguity in which them could be inferred to refer to John and Mary.

Gender Agreement specifies that referents and referring expressions must use the same gender.

Example: 18.34 John has an Acura. He is attractive.
Example: 18.35 John has an Acura. It is attractive.

Syntactic Constraints

Various syntactic constraints may govern possible referent and referring expression combinations.

Example: 18.36 John bought himself a new Acura.¹
Example: 18.37 John bought him a new Acura.
¹ This calls to mind a common syntactic violation:
  The president asked Jim and myself to be her emissaries.

Example: 18.38 John said that Bill bought him a new Acura.
Example: 18.39 John said that Bill bought himself a new Acura.

Selectional Restrictions refer to controls that a verb may wield over its arguments.

Example: 18.45 John parked his Acura in the garage. He had driven it around for hours.
(This example is reminiscent of Groucho Marx's — "One morning I shot an elephant in my pajamas. How he got into my pajamas, I'll never know.")

Knowledge extrinsic to the discourse may have a bearing on the selectional restrictions.

Example: 18.47 John parked his Acura in the garage. It is incredibly messy, with old bike parts lying around everywhere.
Example: 18.48 John parked his Acura in downtown Beverly Hills. It is incredibly messy, with old bike parts lying around everywhere.

Pronoun Interpretation

In addition to strict constraints that govern referent resolution, additional preferred interpretations may apply.

Recency
Example: 18.49 John has an Integra. Bill has a Legend. Mary likes to drive it.

Grammatical role
Example: 18.50 John went to the Acura dealership with Bill. He bought an Integra. [he = John]
Example: 18.50 John and Bill went to the Acura dealership. He bought an Integra. [he = ??]

Repeated mention
Example: 18.53 John needed a car ... He decided he wanted ... Bill went to the Acura dealership with him. He bought an Integra. [he = John]

Parallelism
Example: 18.54 Mary went with Sue to the Acura dealership. Sally went with her to the Mazda dealership. [her = Sue]

Verb semantics
Example: 18.56 John telephoned Bill. He lost the pamphlet on Acuras.
Example: 18.57 John criticized Bill. He lost the pamphlet on Acuras.
(Cf, implicit causality of a verb.)