Functions of noun phrases

Referential
- Definite
  1. We're going to have to talk to him.
  2. We're going to have to talk to Phil.
  3. We're going to have to talk to the hoodlum who lives next door.
  4. Bring me the largest tomato in the garden.
  5. Get off at the stop after the one where I get off.
  6. ?Get off at the stop before the one where I get off.
- Indefinite
  1. There's a red car coming.
  2. Alice is married to a hoodlum.
- Generic (referential?)
  1. Hoodlums are found in every society.
  2. The hoodlum is not an endangered species.
  3. A hoodlum can cause a lot of trouble in class.
Non-referential
- Indefinite non-specific
  1. Paula wants to marry a hoodlum. (ambiguous; could also be indefinite referential)
  2. I'm looking for a book on the cooking of mushrooms. (ambiguous; could also be indefinite referential)
- Indefinite predicative
  1. George is a hoodlum.
- Definite attributive
  1. I'd like to get my hands on whoever did this to my car.
  2. I'd like to get my hands on the hoodlum who did this to my car.
  3. Who is the man drinking the martini? (ambiguous; could also be definite referential, and probably is)

Natural language generation as planning

Utterances as acts with particular goals in mind (speech act theory (Searle, Austin)); language generation as planning acts to achieve goals
This approach allows us to see how acts with very different forms may achieve the same goals (indirect speech acts)
- X says to Y: Please pass the salt.
- X says to Y: Could I have the salt?
- X says to Y: I can't reach the salt.
- X says to Y: I need some salt.
- X says to Y: Salt, please.
- X gets Y's attention and then points to the salt shaker.
inform acts: get the Hearer (H) to believe the proposition (P) or (better) get H to believe that the speaker (S) believes P
request acts: get H to perform the act (A) or (better) get H to believe that S wants A performed
question acts: request of an inform
Concept activation goals: a subgoal under a goal that is "about" the concept (for example, an inform about the concept)
Two kinds of acts with concept activation goals: referring, pointing

Issues in planning and generating referring expressions

Providing enough information in the description so that the hearer can "find" the referent of the NP, but not so much that the hearer is bored or insulted
When is too little or too much information tolerated?
- I'm sorry I couldn't make it to class; I had to have surgery on my eye.
- Could you tell me where the bathroom is? (there might be more than one bathroom)
- Please use that yellow tomato on the counter for your salad. (there is only one tomato on the counter)
Reasoning about mutual knowledge/belief; copresence heuristics: based on S's and H's coprescence in context X, assume mutual knowledge of all of the objects and states in X
Actions that subsume other actions.
- Could you finish eating that awful pizza that's in the refrigerator?
- The adjective awful is, on the surface, part of the referring act, but it can function as an informing act:
  Could you finish eating the pizza that's in the refrigerator? + The pizza is awful.
The planning of a sentence with 3 NPs (example from Appelt)
Remove the pump with the wrench in the toolbox.
- S wants to get H to remove a pump from a platform.
- S plans to request that H remove the pump from the platform.
- S reasons that removing the pump requires unfastening. Precondition for H doing this is that H know what the right tool is. S plans to inform H that the tool is a particular wrench that H knows of.
- S decides he does not need to mention that the pump is to be removed from the platform because it is mutually believed that the platform is the only object to which the pump is attached.
- The pump can be referred to simply as the pump because there is only one object in the shared context that is mutually believed to be a pump.
- S realizes that the informing action (which wrench to use) can be subsumed by the request because the verb remove can take an instrument NP with X (implying "and use X to do it").
- In order to perform the removing, H must have the wrench. For this to happen, she must know where it is, go there and get it. So S plans to inform H where the wrench is. Again subsumption is possible; the location is added to the description for the NP referring to the wrench: in/at/on, etc. Y (implying "and you can find it in/at/on, etc. Y").
- The final sentence does the work of three sentences:
  Remove the pump. Use the wrench to remove the pump. The wrench is in the toolbox.

Generating referring expressions

Steps
- Content determination; output: attribute-value pairs
- Realization
Corpora and shared tasks
- TUNA:
  - Annotated referring expressions for task in which one piece of furniture or face must be distinguished from others
  - Attribute Selection for Referring Expressions Generation: Map an input representation from the TUNA corpus to an attribute set that identifies a target referent
- GREC
  - Annotated articles, giving referring expressions for main subject references (GREC-MSR) or people (GREC-NEG)
  - Given a set of alternative expressions for a main subject reference from the GREC corpus, select an appropriate one
```
<TEXT ID="1">
    <PARAGRAPH>
        ...
        <REF ID="1.2" TYPE="np-subj" CAT="country" ALT="Brunei; Brunei
	 itself; _; it; it itself; that; that itself; the country; the
	 country itself; which; which itself">Brunei</REF>, the
	remnant of a very powerful sultanate, became independent from
	Great Britain in 1984.
    </PARAGRAPH>
    <PARAGRAPH>
        ...
    </PARAGRAPH>
  </TEXT>
```
  - GREC-NEG: selecting appropriate referential expressions for mentions of people in Wikipedia articles
    Daniel David Palmer or D.D. Palmer (March 7, 1845 - October 20, 1913) was the founder of Chiropractic.
    Palmer was born in Pickering, near Toronto, Canada to Katherine McVay and Thomas Palmer. At age twenty he moved to the United States with his family. Palmer held various jobs as a beekeeper, school teacher, and grocery store owner, and had an interest in the various health philosophies of his day, such as magnetic healing, and Spiritualism. Palmer practiced magnetic healing beginning in the mid-1880s in Burlington and Davenport, Iowa.
- Generating Instructions in Virtual Environments
  - Transcripts of human instructions guiding another human through a virtual 3D environment as they play a game
  - Given a description of a virtual 3D environment, a set of tasks, and representation of the position and orientation of a human player, guide the player through the environment
Evaluation
- Criteria
  - Descriptive adequacy of output (does it uniquely identify the referent?)
  - Similarity to human-generated descriptions
  - Correctness of human reponses to system-generated descriptions