Generating Natural Language Under Pragmatic Constraints

Eduard H. Hovy

• Publisher: Psychology Press
• Year: 2013
• ISBN:
  9781134742219
• Edition: 1
• Topic: Psicologia
• Subtopic: Storia e teoria della psicologia

Recognizing that the generation of natural language is a goal- driven process, where many of the goals are pragmatic (i.e., interpersonal and situational) in nature, this book provides an overview of the role of pragmatics in language generation. Each chapter states a problem that arises in generation, develops a pragmatics-based solution, and then describes how the solution is implemented in PAULINE, a language generator that can produce numerous versions of a single underlying message, depending on its setting.

Chapter 1

Introduction

1.1 Things People Say

When you compare the language produced by people to the text produced by existing language generation programs, one thing becomes clear immediately: people can say the same thing in various ways to achieve various effects, and generators cannot. The generator described in this book, PAULINE (Planning And Uttering Language In Natural Environments), addresses this shortcoming.

It is straightforward to write a language generation program that produces impressive text by associating a sentence template (or some equivalent general grammatical form) with each representational item and then using a grammar to realize the template into surface form. Such a program, however, is not sensitive to anything but the input items, and therefore produces the same output to all hearers in all circumstances.

When we produce language, we tailor our text to the hearer and to the situation. This enables us to communicate more information than is contained in the literal meanings of our words; indeed, the additional information often has a stronger effect on the hearer than the literal content has. This information is carried by both the content and the form of the text:

“Old Bill finally kicked the bucket last night!”

“We are not going to see Uncle Bill any more… ”

“I am very sorry to have to tell you that Bill passed away”

As speakers and hearers, we attach various interpretations of the speaker, his or her goals, the hearer, and the conversational circumstances, to the various ways of expressing a single underlying representation. These interpretations are governed by rules. Speakers use the rules to determine how to say what they want to say. In order to exhibit the same degree of flexibility of expression, generator programs require such rules too.

What, then, is the additional information that speakers can convey? Consider the different points of view the speaker communicates in each of the following four descriptions of an event that happened at Yale University in April 1986:

(a) On April 4, concerned Yale students constructed a shantytown on Boesak Plaza as a reminder to those in Woodbridge Hall (and all over campus and the community) that Yale is complicit (sic) with the system of apartheid that creates shantytowns where thousands of blacks are forced to live in squalor and fear. The shantytown, Winnie Mandela City, served as a focal point of education concerning South Africa and Yale’s investments there. At 5:30 am on April 14 the Yale Administration had the shantytown torn down and had 76 students and community members who were defending the shanties arrested. After a huge outcry, the Administration allowed the shanties to be rebuilt. We will not be silenced; we will continue to challenge the University on their moral failure. (From: protester literature; the protesters renamed the plaza after the South African churchman Allan Boesak)

(b) On April 4, a small group of students took over Beinecke Plaza and built some shanties; they wanted to force Yale to sell its stocks in companies with branches located in South Africa. The university asked the students to move the shanties to another location, but the students refused. The university then granted them permission to occupy the plaza until the end of the week, so that they could be there to be seen by the university’s trustees, the Yale Corporation, at their meeting. But even after the meeting, the students refused to leave the plaza, and police had to clear the shanties. Later, the university relented, and gave them permission to rebuild the shanties. It also announced that it would send a fact-finding mission to South Africa. (Speaker: anti-divestment Yale student)

(c) On April 4, students at Yale built a symbolic shantytown to protest their school’s investments in companies doing business in South Africa. The college ordered the shanties destroyed. The police arrested 76 protesters when the shantytown was torn down. Local politicians and more than 100 faculty members criticized the action. A week after it had ordered the removal of the shantytown – named Winnie Mandela City, after the South African foe of apartheid – the shantytown was reconstructed and the administration agreed to allow it to remain standing. Concurrently, Yale announced that its trustees, the Yale Corporation, would soon send a fact-finding mission to South Africa to investigate the actions of corporations in which it owns between $350 million and $400 million of stock. (From: The New York Times, Sunday, 27 April 1986, Connecticut section)

(d) Some students erected a shantytown to protest Yale’s investments in companies that have operations in South Africa. The University tore it down and arrested several of them. The students continued to demonstrate and finally the university said they could put up the shantytown again. The university said it would investigate its investments in South Africa. (Speaker: neutral student)

Clearly the first two speakers incorporate strongly their opinions about the shantytown issue; the second two speakers seem more neutral but differ in level of formality. But how do you “incorporate opinions” and what does it mean to “seem more neutral” and to “be formal”? There is no single item in the texts that can be pinpointed as carrying the opinion or setting the level or formality; rather, each text seems to contain a number of little clues, and these clues cumulatively convey a certain impression to the reader. What are these little clues? Where do they appear in language and how do we decide to use them? How do they interact? What other impressions — information such as the speaker’s emotional state, social status relative to the hearer, the ways he or she would like to influence the hearer’s future behaviour — can be incorporated into language?

Some additional, rather overt, techniques are used in the following two texts. They date from a labor strike at Yale University in 1984. The first is an excerpt from an open letter to Yale President Giamatti from the university’s clerical and technical workers’ labor union negotiating committee, November 9, 1984:

(e) It is time, in the best interests of all concerned, to settle the strike. It is our understanding that the University administration, as well as the Union, has received a document entitled ‘A Statement of Purpose by the Coalition to End the Strike’. We appreciate the spirit of the document. Clearly, the community earnestly desires and needs a settlement, so that Yale can get back to what it is supposed to be. Our members earnestly want a settlement. You have said that you do, too, and we are prepared to take you at your word. We are willing to compromise significantly to achieve a settlement. Therefore, we propose the immediate resumption of negotiations on a daily basis.

Style is expressly vised to impute blame to the other side: the union “earnestly desires and needs a settlement”; they “are willing to compromise”; they will “take [Yale] at [its] word” that Yale wants a settlement too. Clearly Yale does not really want a settlement! Clearly the union has to prod an unwilling Yale into negotiating! In contrast, compare this excerpt from an open letter from President Giamatti to the Yale community, September 26, 1984:

(f) I write with great disappointment following Local 34’s action in calling a strike against the University. The University negotiating team has made concerted efforts, lately with the help of the Mediator, Eva Robins, to and common ground and to bring about a fair and reasonable settlement of the outstanding issues in a manner satisfactory to both parties. But the agreement has not been achieved.

Giamatti’s response is much calmer, more reasoned: he writes “with great disappointment”; his team has “made concerted efforts”; the agreement “has not been achieved”. It is clear that he is not to blame! His disappointment casts Giamatti as a reasonable man who hopes others will be reasonable too. He even refrains from blaming the union for the failure of the settlement… Similar techniques appear in the shantytown texts. In example (a), for instance, the protesters say “concerned Yale students”; “constructed a shantytown… as a reminder”; Yale “had 76 students… arrested”; “a huge outcry” — clearly they are a well-meaning, harmless lot with much popular support. But what about the opposing account (b), containing “a small group of students”; “took over Beinecke Plaza”; “they wanted to force Yale to… ”; “police had to clear the shanties”? Obviously the university did its best to remain conciliatory even when dealing with a few radicalized students!

1.2 Things PAULINE Says

PAULINE, the computer program described here, uses strategies based on these techniques to produce various texts from underlying representations. In all, it has been tried on three distinct episodes. The first set of examples are generated from a representation of the shantytown episode. From a single representation — a network of about 120 representation elements — PAULINE produces over 100 different texts. For example, as an informal description of the issue, PAULINE says:

Example 1.

YALE UNIVERSITY PUNISHED A NUMBER OF STUDENTS FOR BUILDING A SHANTYTOWN ON BEINECKE PLAZA BY ARRESTING 76 STUDENTS AND TEARING IT DOWN ONE MORNING IN EARLY APRIL. THE STUDENTS WANTED YALE TO DIVEST FROM COMPANIES DOING BUSINESS IN SOUTH AFRICA. FINALLY. THE UNIVERSITY GAVE IN AND ALLOWED THE STUDENTS TO REBUILD IT.

This is the kind of description one may hear from a passerby who knows about the issue. Compare this with the following version, in which PAULINE, now being a journalist, uses much more formal language for its newspaper article (including, for example, such conjunctive phrases as “so that” and “concurrently”, such verbs as “construct”, “request”, and “give permission”, and the passive mode):

Example 2.

IN EARLY APRIL. A SHANTYTOWN … NAMED WINNIE MANDELA CITY … WAS CONSTRUCTED BY SEVERAL STUDENTS ON BEINECKE PLAZA SO THAT YALE WOULD DIVEST FROM COMPANIES DOING BUSINESS IN SOUTH AFRICA. THE LOCAL COMMUNITY SUPPORTED THE ACTION. AT 5:30 AM ON APRIL 14. THE SHANTYTOWN WAS DESTROYED BY OFFICIALS; ALSO. AT THAT TIME. THE POLICE ARRESTED 76 STUDENTS. THE STUDENTS REQUESTED THAT THE UNIVERSITY GIVE THEM PERMISSION TO REASSEMBLE THE SHANTYTOWN WHILE SEVERAL LOCAL POLITICIANS AND FACULTY MEMBERS EXPRESSED CRITICISM OF YALE’S ACTION. FINALLY, THE UNIVERSITY PERMITTED THE STUDENTS TO RECONSTRUCT IT AND. CONCURRENTLY, YALE ANNOUNCED THAT A COMMISSION WOULD GO TO SOUTH AFRICA IN JULY TO EXAMINE THE SYSTEM OF APARTHEID.

Examples 1 and 2 are fine ways to introduce someone to the topic. They are the kind of thing we would say if we were unbiased informers, such as passersby and reporters. But what if we were protesters and were trying to convince someone of our opinion? When PAULINE is set up to produce text supporting the protesters’ cause, i.e., when it is given the goals to slant its description of the episode toward the protesters, it produces:

Example 3.

AS A REMINDER TO YALE UNIVERSITY TO DIVEST FROM COMPANIES DOING BUSINESS IN SOUTH AFRICA. A LARGE NUMBER OF CONCERNED STUDENTS ERECTED A SHANTYTOWN … NAMED WINNIE MANDELA CITY … ON BEINECKE PLAZA IN EARLY APRIL. THE LOCAL COMMUNITY EXPRESSED SUPPORT FOR THE STUDENTS’ ACTION. THE UNIVERSITY TOLD THE STUDENTS TO ERECT THE SHANTYTOWN ELSEWHERE. LATER. AT 5:30 AM ON APRIL 14. THE SHANTYTOWN WAS DESTROYED BY OFFICIALS; ALSO. AT THAT TIME, THE POLICE ARRESTED 76 STUDENTS. THE STUDENTS REQUESTED THAT YALE UNIVERSITY GIVE THEM PERMISSION TO REASSEMBLE IT ON BEINECKE PLAZA AND AT THE SAME TIME SEVERAL LOCAL POLITICIANS AND FACULTY MEMBERS EXPRESSED CRITICISM OF YALE’S ACTIONS. FINALLY, YALE PERMITTED THE STUDENTS TO RECONSTRUCT THE SHANTYTOWN AND. CONCURRENTLY. THE UNIVERSITY ANNOUNCED THAT A COMMISSION WOULD GO TO SOUTH AFRICA IN JULY TO EXAMINE THE SYSTEM OF APARTHEID.

In contrast, when PAULINE has to produce the official Yale version, it says:

Example 4.

IN EARLY APRIL. A SMALL NUMBER OF STUDENTS WERE INVOLVED IN A CONFRONTATION WITH YALE UNIVERSITY OVER YALE’S INVESTMENT IN COMPANIES DOING BUSINESS IN SOUTH AFRICA. THE STUDENTS CONSTRUCTED A SHANTYTOWN … NAMED WINNIE MANDELA CITY … ON BEINECKE PLAZA IN ORDER TO FORCE THE UNIVERSITY TO DIVEST FROM THOSE COMPANIES. YALE REQUESTED THAT THE STUDENTS ERECT IT ELSEWHERE. BUT THEY REFUSED TO LEAVE. THE UNIVERSITY INTENDED TO BE REASONABLE. THE UNIVERSITY GAVE IT PERMISSION TO EXIST UNTIL THE MEETING OF THE YALE CORPORATION. BUT EVEN AFTER THAT THE STUDENTS STILL REFUSED TO MOVE. AT 5:30 AM ON APRIL 14. OFFICIALS HAD TO DISASSEMBLE THE SHANTYTOWN. FINALLY. YALE. BEING CONCILIATORY TOWARD THE STUDENTS. NOT ONLY PERMITTED THEM TO RECONSTRUCT IT. BUT ALSO ANNOUNCED THAT A COMMISSION WOULD GO TO SOUTH AFRICA IN JULY TO EXAMINE THE SYSTEM OF APARTHEID.

Of course, this is not the way a protester or Yale official would tell you the story in person. For one thing, they may cut it a little shorter, and for another, they will be less formal and more openly opinionated. PAULINE illustrates:

Example 5.

I AM ANGRY ABOUT YALE’S ACTIONS. THE UNIVERSITY HAD OFFICIALS DESTROY A SHANTYTOWN CALLED WINNIE MANDELA CITY ON BEINECKE PLAZA AT 5:30 AM ON APRIL 14. A LOT OF CONCERNED STUDENTS BUILT IT IN EARLY APRIL. NOT ONLY DID YALE HAVE OFFICIALS DESTROY IT. BUT THE POLICE ARRESTED 76 STUDENTS. AFTER THE LOCAL COMMUNITY’S HUGE OUTCRY, THE UNIVERSITY ALLOWED THE STUDENTS TO PUT THE SHANTYTOWN UP THERE AGAIN.

Example 6.

IT PISSES ME OFF THAT A FEW SHIFTLESS STUDENTS WERE OUT TO MAKE TROUBLE ON BEINECKE PLAZA ONE DAY: THEY BUILT A SHANTYTOWN. WINNIE MANDELA CITY. BECAUSE THEY WANTED YALE UNIVERSITY TO PULL THEIR MONEY OUT OF COMPANIES WITH BUSINESS IN SOUTH AFRICA. I AM HAPPY THAT OFFICIALS REMOVED THE SHANTYTOWN ONE MORNING. FINALLY. YALE GAVE IN AND...

Table of contents

• Front Cover
• Half Title
• Title Page
• Copyright
• Dedication
• Contents
• Preface
• 1 Introduction
• 2 Pragmatics
• 3 Interpretation in Generation
• 4 Affect in Text
• 5 Creating Style
• 6 Grammar and a Phrasal Lexicon
• 7 Planning and Realization
• 8 A Review of Language Generation
• Appendices
• Bibliography
• Name Index
• Topic Index