16.3481, Review: Semantics/Computational Ling: Mani et al (2005)

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Subject: 16.3481, Review: Semantics/Computational Ling: Mani et al (2005)

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1)
Date: 05-Dec-2005
From: Anil Singh < anil_phdcl at yahoo.co.in >
Subject: The Language of Time: A Reader 

	
-------------------------Message 1 ---------------------------------- 
Date: Tue, 06 Dec 2005 23:16:47
From: Anil Singh < anil_phdcl at yahoo.co.in >
Subject: The Language of Time: A Reader 
 

EDITORS: Mani, Inderjeet; Pustejovsky, James; Gaizauskas, Robert 
TITLE: The Language of Time
SUBTITLE: A Reader
PUBLISHER: Oxford University Press 
YEAR: 2005
Announced at http://linguistlist.org/issues/16/16-2411.html 

Anil Kumar Singh, Language Technology Research Centre (LTRC), 
IIIT, Gachibowli, Hyderabad-500019 (A.P.), India.

OVERVIEW

Natural language (NL) can convey all kinds of information about the 
world, abstract or concrete, real or hypothetical. Temporal information 
is one of the most important aspects of whatever we want to express 
using NL. This book presents a collection of some of the well known 
papers on temporal information in NL. The focus seems to be on the 
computational point of view. However, papers on linguistic and 
philosophical issues have been included to provide enough 
background. Since scholars and researchers from diverse fields 
(philosophy, linguistics, psychology, natural language processing, 
artificial intelligence) have contributed to the study of time in NL, the 
editors have made an attempt to represent all of these. The book can 
be useful for anyone interested in time and/or language.

The book is divided into four parts and there is a very informative 
introduction to each of these parts. These introductions make the 
papers accessible to even those without the required background as 
they summarize and connect the papers. Some readers who are 
looking just for a quick overview of the study of time in NL might want 
to read only the introductions.

In all, the book contains 29 important papers. These papers cover 
theories as well as computational approaches for studying (or 
computing) time in NL. People working in the relevant fields are 
already familiar with many of these.

The first part has 8 papers on tense, aspect and event structure. The 
second part is about temporal reasoning and it consists of 6 papers. 
The third part has 8 papers on temporal structure of discourse. The 
fourth part puts together 7 papers on temporal annotation.

SYNOPSIS

Chapter 1
The first part starts with Vendler's well known paper ('Verbs and 
Times') on verb classification with respect to time (or tense). Vendler 
claims (a claim more or less accepted by many authors of the following 
papers) that almost all the verbs can be classified into a few classes, 
at least in their most dominant sense. The classes that he comes up 
with after a very interesting and enjoyable discussion are those of 
states, activities (or processes), accomplishments and achievements. 
This four way classification is the starting point of a lot of work done 
on time in language. Perhaps this is why Vendler's is the first paper in 
the book, although it is not the earliest among those included in the 
book.

Chapter 2
The second paper is on 'the syntax of event structure' by Pustejovsky. 
He argues that grammatical phenomena make reference to the 
internal structure of events, and that a subeventual analysis for 
predicates is able to systematically capture these effects. This paper 
represents a major stream in semantics. The purpose is to show that 
verbs decompose into distinct event types with internal structure. The 
primary components of an event structure are the event type (of the 
lexical item), the rules of event decomposition and the rules to map to 
lexical structure. Pustejovsky considers three basic event types: 
states, processes and transitions. He also relates event structure with 
lexical conceptual structure (LCS). Problems like adverbial 
modification are discussed in terms of event structure. On the whole it 
is a long but very readable paper which makes a convincing case for 
looking at verbs as events with an internal structure. As the editors 
point out in the introduction, this approach can avoid proliferation of 
primitives, which is a major problem with schemes like that of Dowty's 
(Dowty, 1979). A limitation is that event structure is not directly related 
with temporal structure.

Chapter 3
Pustejovsky's paper is followed by Emmon Bach's 'Algebra of Events'. 
The starting point for this paper is the close parallels between the 
mass count distinction in nominal systems and the aspectual 
classification  of verbal expressions. Bach expresses one of the 
parallels as a proportion: events:processes::things:stuff, drawing on 
Link's paper on count-mass-plural domain (Link, 1983). His algebra 
deals with the distinctions based mainly on Carlson's classification 
(Carlson, 1981), which subdivides achievements in two categories 
(happenings and culminations, e.g. recognize and die). It also, in a 
way, takes into account the structure of events and processes. Link's 
scheme treats sets of individuals ('John and Mary') as super-
individuals formed by a join operation. The super-individual is made of 
the stuff that the individuals are made of. Bach's contention is that telic 
events are also formed of process 'stuff'.

Chapter 4
The fourth paper is Reichenbach's classic work called 'The Tenses of 
Verbs' (Reichenbach, 1947). The primary idea is that the times of 
events can be located with respect to a deictic centre, which makes 
them similar to pronouns (the anaphoric view of tenses). In 
Reichenbach's scheme, there can be references to three time points: 
the speech time (S), the event time (E) and the reference time (R). 
These three time points can be related by 'precedes' or 'simultaneous' 
relations. Depending on the relations between S, E and R, we can 
define all the possible tenses. For example, E=R< S would be simple 
past, whereas S=R=E would be simple present. Only seven out of the 
thirteen possible relations are realized in English. This is perhaps the 
most influential paper in the book. This approach to analyze tenses 
has come to be known as the Reichenbachian approach. Quite apart 
from its influence however, the paper is remarkable for the way it is 
written. It is not divided into sections, there is no conclusion, nor are 
there any references. One wonders how the reviewers would react if a 
paper like this was submitted to a natural language processing (NLP) 
conference in this age of LaTex stylesheets. Anyway, I found this 
paper to be as enjoyable as it is influential.

Chapter 5
The next paper is 'Tense Logic and the Logic of Earlier and Later' 
(Prior, 1968). Prior presents a tense logic which is an extension of E. 
J. Lemmon's minimal tense logic Kt. He also relates it to the minimal 
calculus of earlier-later relation. He adds two operators G ('is always 
going to be') and H ('has always been') to the two operators provided 
by Kt: P (past) and F (future). The earlier-later calculus uses 
operators T and U such that 'Tap' means 'It is the case at instant a 
that p' and 'Uab' means that 'The instant a is earlier than instant b'. 
The tense logic is built upon in stages in the paper so as to get four 
logical systems of increasing power. This paper is also an important 
one, but it is not as easy to read as the some of the other papers in 
the book, partly due to the 'somewhat opaque prefix notation'.

Chapter 6
The paper by Moens and Steedman counters the idea that linguistic 
categories are related to a linear model of time. Their ontology is 
based on a mental representation of events structured on more than 
purely temporal principles. Their aspectual categories are a modified 
form of the Vendlerian classes. States are distinguished from events, 
which in turn can be classified in four categories depending on 
whether there are consequences and whether the events are atomic 
or extended. Aspectual type of a proposition can change due to 
modifiers. Such 'aspectual coercion' can be explained in terms of a 
transition network, which represents an aspect calculus. Another 
central notion in their ontology is that of 'nucleus' ('a structure 
comprising a culmination, an associated preparatory process, and a 
consequent state'). This nucleus plays a role in many of the 
permissible transitions in the network. However, as the editors point 
out, the paper doesn't offer rules for compositional semantics.

Chapter 7
Dorr and Olsen use LCS representation of Levin's classes. The 
aspectual classed are defined in terms of three features (telicity, 
dynamicity and durativity). In their system, features can only get 
added, not deleted. These aspectual features can be used to help in 
machine translation and generation.

Chapter 8
The last paper in the first part is by Passonneau, describing the 
PUNDIT information extraction system. She focuses only on actual 
(realis) events. A three step method is used to find the actual time 
associated with an event (if there is any), determine the temporal 
structure of the situation, and locating the situation with respect to the 
time of text production or to the times of other situations. The features 
used for events are situation type (state, process, or transition event), 
kinesis (active or stative) and boundedness (bounded, unbounded, or 
unspecified).

Chapter 9
The second part begins with a long but enjoyable paper (except 
perhaps the example about a Republican President) by McDermott. 
He presents a 'temporal logic for processes and plans'. One important 
idea in this logic is that of temporal chronicles ('a complete possible 
history of the universe'). The chronicles are arranged in the form of a 
tree in which branching occurs only towards the future. This is meant 
to model future possibility. McDermott defines events as sets of 
intervals over which a proposition is minimally (at least once) true.

Chapter 10
'A logic based calculus of events' is presented by Kowalsky and 
Sergot. They concentrate on applying event calculus for database 
updates as well as simple narratives. Instead of rejecting an update 
conflicting with the existing information, the update is accepted and 
the conflicting information is withdrawn. Some predicates introduced 
are 'Holds', 'HoldsAt', 'initiates', 'terminates' and 'happens'.

Chapter 11
Indeterminant temporal anchoring and granularity is taken into 
account by Chittaro and Combi in framework called 'Temporal 
Granularity and Indeterminacy Event Calculus (TGIC)'. Event calculus 
determines the maximal validity intervals (MVIs) over which
properties hold. Their definition of MVI accommodates a more general 
concept of event.

Chapter 12
Here is another very influential paper, this time by James F. Allen. It 
presents a 'general theory of action and time'. This theory seeks to 
take care of actions that involve non-activity, actions not 
decomposable into subactions and actions which occur simultaneously 
and interact with others. Allen uses thirteen basic interval relations 
like 'before', 'after', 'meet', 'during', etc. There are three classes 
(property, event and process) and one metalanguage predicate 
(HOLDS, OCCUR, OCCURRING) associated with each of these 
classes.

Chapter 13
Galton's paper is a critical revision of Allen's work. He 'reinstates' 
instants to give a combined instant-interval scheme in which instants 
either fall within or limit intervals. One of the reasons for this revision 
of Allen's theory is to accommodate continuous change. The HOLD 
and OCCURS predicated are each split into three (HOLDS-ON, 
HOLDS-IN, HOLDS-AT).

Chapter 14
The paper by Hobbs and Pustejovsky on TimeML (originally DAML-
Time), a markup language for annotating temporal information in a 
discourse. They also relate it to OWL-Time ontology. It takes into 
account the formal theories of time that have been suggested during 
the last many decades. This paper can be a good introduction to 
TimeML, which might become a standard.

Chapter 15
Though Dowty's 1979 paper is not included, there is one by him 
on 'the effect of aspectual class on the temporal structure of 
discourse'. His analysis is based on a compositional theory of aspect, 
i.e., aspectual classes of lexical items combine to give the aspectual 
classes of sentences. He also uses a pragmatic principle called 
Temporal Discourse Interpretation Principle (TDIP) which basically 
says that the reference time advances forward with each utterance, 
unless there is a temporal adverbial. He discusses some other 
pragmatic principles like the perspective of the narrator, expectations 
about discourse conventions (Grice's maxims) and background 
knowledge.

Chapter 16
Lascarides and Asher take further the work on including pragmatics in 
discourse (with respect to temporal relations). There work is more 
formal, based on the notion of 'defeasible reasoning' (based on 
default knowledge that can be overridden).

Chapter 17
In this chapter, Bell extends the Labovian analysis of temporal 
discourse structure. They focus on news stories and claim that the 
narrative in these stories can be segmented into 'abstract', 'attribution' 
and 'story', each of which can have further segmentation. The stories 
also contain many 'episodes', which in turn contain events.

Chapter 18
Here Webber extends the Reichenbachian notion of tense as 
discourse anaphor. She also related this to the work on discourse by 
Grosz and Sidner. The main elements of her approach are temporal 
focus, a tripartite ontology of events (preparation, culmination and 
consequence), 'specification' of entities by anaphors, and a 'focus 
stack' mechanism for resumption of dialog segments.

Chapter 19
Song and Cohen present an algorithm for using tense interpretation in 
analyzing simple narratives. They also use a modified Reichenbachian 
scheme for representing tenses which is more precise and 
unambiguous (uses one SRE triple instead of three structures for 
future perfect). Their algorithm is based on temporal focus, a tense 
hierarchy (for English) and constraints on coherent tense sequences.

Chapter 20
The automatic temporal reference resolution system described by 
Wiebe et al. works on the ambiguous output of a semantic parser. The 
domain they have considered is scheduling dialogs (''How about 
two?'', ''Twelve to two.''). In their model, a 'temporal unit' is associated 
with the current and the preceding utterance. A temporal unit has 
fields which are partially ordered with respect to specificity. Some 
resolution rules are also used.

Chapter 21
Hwang and Schubert use a novel 'fine structure' of discourse, 
namely 'tense trees'. Tense trees differ from simple 
Reichenbachian 'lists'. Given that the sentences are not 'flat' (as 
seems to have assumed by some, as far as studies of temporal 
structure in discourse are concerned), tense trees can be used to 
more effectively (compositionally) analyze tense and aspect.

Chapter 22
Hitzeman et al. use an HPSG implementation of discourse grammar 
for determining the temporal structure of the discourse. They try to 
take into account the mutually constraining effect of tense, aspect, 
temporal adverbials and rhetorical relations to reduce ambiguity. 
Another suggestion is to use underspecified representation of 
temporal or rhetorical structure, again for reducing ambiguity.

Note: The page numbers in the references given on the first page of 
the book for chapters 23-26 (from the ACL 2001 workshop) seem to 
be wrong. See the references below for the correct information.

Chapter 23
Wilson et al. present an annotation framework for automatically 
marking up temporal information. The annotation scheme is TIMEX2, 
which has been incorporated into TimeML. Their system tries to 
achieve cross-lingual reusability. Some updates since the publication 
of the paper are also mentioned.

Chapter 24
Another technique for temporal annotation is described by Katz and 
Arosio. In their scheme ('a radically simplified semantic formalism'), 
each verb is associated with a temporal interval and there are 
relations among these intervals. The relations are encoded with 
directed 'secondary edges' representing 'precedence' and 'inclusion' 
relations and their duals. They also discuss the relations between 
annotations, i.e., whether they are equivalent, consistent, or 
inconsistent, or whether one subsumes the other.

Chapter 25
Another temporal extraction system has been described by Filatova 
and Hovy. They break up news stories into clauses representing 
events and then assign time stamps to these events. Tense 
information in the clauses is used to help in timestamping.

Chapter 26
This paper (Schilder and Habel) describes a semantic tagging system 
for extracting temporal information from news messages. The tagger 
looks for dates, prepositional phrases and situational verbs. It marks 
chunks of texts containing temporal information and also tries to 
extract this information. Temporal relations (based on Allen's theory) 
are identified partly by prepositions.

Chapter 27
This chapter presents in detail the specification language TimeML. 
While the other paper (Chapter 14) is more theory oriented, this one is 
more about the definition of TimeML and guidelines for annotation 
using this language. It is compulsory reading for anyone involved with 
actual annotation of temporal information, or even with annotation in 
general.

Chapter 28
Li et al. present a framework for mapping linguistic patterns to 
temporal relations. It uses 'temporal concept frames' (activity related 
or time related), temporal relations (relative or absolute), temporal 
indicators (time related words), rules for temporal references and 
rules for rules for resolving conflicts. They have tried their system for 
Chinese with good results.

Chapter 29
The last paper (Setzer et al.) is about comparing and evaluating 
temporal annotations using the idea of 'temporal closure', which can 
help in deciding whether two annotations are equivalent or not. The 
paper also suggests ways to make manual annotation easier by 
computing closure of an annotation. A precise way of evaluating 
annotations is presented.

EVALUATION

This book brings together a variety of approaches, theoretical as well 
practical, for dealing with time in NL. The papers are among the most 
relevant. They have been arranged in an order which makes sense. 
The introductions are excellent too. Perhaps the division into four 
parts and an introduction for each of them is best way to bring 
together a lot of diversity. However, one wonders whether a small 
introduction to each paper (instead of a long one to each part), 
together with a chapter in the beginning looking at the big picture 
wouldn't have been better. As it is, the readers might miss the 
connections between the successive chapters in some cases. And 
one can also complain about some missing papers (like Dowty, 1979), 
but that is unavoidable in any collection of papers. On the whole, it 
was rewarding to read this book. It might become a compulsory 
reading for people working in the relevant disciplines, and there are 
quite a few of them (people as well disciplines).

REFERENCE

Dowty D. R. (1979). Word Meaning and Montague Grammar: the 
Semantics of Verbs and Times in Generative Semantics and 
Montague's PTQ. Reidel.

REFERENCES TO THE ORIGINAL PUBLICATION OF THE 
CONTENTS OF THIS BOOK

1. Vendler Z. (1967). Verbs and Times. Ch. 4 of 'Linguistics in 
Philosophy', 97-121. Cornell University Press.

2. Pustejovsky James (1991). The Syntax of Event Structure. 
Cognition, 41. Elsevier.

3. Bach Emmon (1986). The Algebra of Events. 'Linguistics and 
Philosophy', 9, 5-16. Swets and Zeitlinger Publishers.

4. Reichenbach Hans (1947). The Tenses of Verbs. Section 51 
of 'Elements of Symbolic Logic', 287-298. The Macmillan Company, 
New York.

5. Prior A. N. (1968). Tense Logic and the Logic of Earlier and Later. 
Chapter 11 of 'Papers on Time and Tense', 116-134. Oxford 
University Press, Oxford.

6. Moens Marc and Steedman Mark (1988). Temporal Ontology and 
Temporal Reference. Computational Linguistics 14(2), 15-28. 
Association for Computational Linguistics.

7. Dorr Bonnie J. and Olsen Mari Broman (1997). Deriving Verbal and 
Compositional Lexical Aspect for NLP Applications. Proceedings of the 
35th Annual Meeting of the Association for Computational Linguistics, 
151-158. Association for Computational Linguistics.

8. Passonneau Rebecca J. (1988). A Computational Model of the 
Semantics of Tense and Aspect. Computational Linguistics, 14(2), 15-
28. Association for Computational Linguistics.

9. McDermott Drew (1982). A Temporal Logic for Reasoning About 
Processes and Plans. Cognitive Science 6, 101-155. Cognitive 
Science Society.

10. Kowalski Robert and Sergot Marek (1986). A Logic-Based 
Calculus of Events. New Generation Computing, 4, 67-94. Ohmsha 
Ltd.

11. Chittaro Luca and Combi Carlo (2000). Extending the Event 
Calculus with Temporal Granularity and Indeterminacy. In Bettini C. 
and Montanari A. (eds.), 'Spatial and Temporal Granularity: Papers 
from the AAAI Workshop'. Technical Report WS-00-08. The AAAI 
Press.

12. Allen James F. (1984). Towards a General Theory of Action and 
Time. Artificial Intelligence, 23, 123-154. Elsevier.

13. Galton Antony (1990). A Critical Examination of Allen's Theory of 
Action and Time. Artificial Intelligence, 42, 159-188. Elsevier.

14. Hobbs Jerry R. and Pustejovsky James (2003). Annotating and 
Reasoning About Time and Events.  Proceedings of the AAAI Spring 
Symposium on Logical Formalization of Commonsense Reasoning. 
Stanford University, CA.

15. Dowty David R. (1986). The Effects of Aspectual Class on the 
Temporal Structure of Discourse: Semantics or Pragmatics? 
Linguistics and Philosophy, 9, 37-61. Swets and Zeitlinger.

16. Lascarides Alex and Asher Nicholas, (1993). Temporal Relations, 
Discourse Structure, and Commonsense Entailment. Linguistics and 
Philosophy, 16, 437-493. Kluwer Academic Publishers.

17. Bell Allan (1999). News Stories as Narratives. In Jaworski A. and 
Coupland N. (eds.), 'The Discourse Reader', 236-251. Routledge.

18. Webber Bonnie Lynn (1988). Tense as Discourse Anaphor. 
Computational Linguistics, 14(2), 61-73. Association for Computational 
Linguistics.

19. Song Fei and Cohen Cohen, (1991). Tense Interpretation in the 
Context of Narrative. Proceedings of the Ninth National Conference 
on Artificial Intelligence (AAAI-91), 131-136. American Association for 
Artificial Intelligence.

20. Wiebe Janyce, O'Hara Tom, McKeever Kenneth, Ohrstrom-
Sandgren Thorsten (1997). An Empirical Approach to Temporal 
Reference Resolution. Proceedings of the Second Conference on 
Empirical Methods in Natural Language Processing (EMNLP-97), 174-
186. Association for Computational Linguistics and SIGDAT.

21. Hwang Chung Hee and Schubert Lenhart K. (1992). Tense Trees 
as the Fine Structure of Discourse. Proceedings of the 30th Annual 
Meeting of the Association for Computational Linguistics, 232-240. 
Association for Computational Linguistics.

22. Hitzeman Janet and, Moens Mark and Grover Claire (1995). 
Algorithms for Analyzing the Temporal Structure of Discourse. 
Proceedings of the Annual Meeting of the European Chapter of the 
Association for Computational Linguistics, 253-260. Association for 
Computational Linguistics.

23. Wilson George, Mani Inderjeet, Sundheim Beth and Ferro Lisa 
(2001). A Multilingual Approach to Annotating and Extracting 
Temporal Information. Proceedings of the ACL 2001 Workshop 
Temporal and Spatial Information Processing, 81-87. Association for 
Computational Linguistics.

24. Katz Graham and Arosio Fabrizio (2001). The Annotation of 
Temporal Information in Natural Language Sentences. Proceedings of 
the ACL 2001 Workshop Temporal and Spatial Information 
Processing, 104-111. Association for Computational Linguistics.

25. Filatove Elena and Hovy Eduard, (2001). Assigning Time-Stamps 
to Event-Clauses. Proceedings of the ACL 2001 Workshop Temporal 
and Spatial Information Processing, 88-95. Association for 
Computational Linguistics.

26. Schilder Frank and Habel Christopher (2001). From Temporal 
Expressions to Temporal Information: Semantic Tagging of News 
Messages. Proceedings of the ACL 2001 Workshop Temporal and 
Spatial Information Processing, 65-72. Association for Computational 
Linguistics.

27. Pustejovsky James, Ingria Robert, Sauri Roser, Castano Jose, 
Littman Jessica, Gaizauskas Rob, Setzer Andrea, Katz Graham, Mani 
Inderjeet (2004). The Specification Language TimeML. This volume, 
545-557. Oxford University Press.

28. Li Wenjie, Wong Kam-Fai and Yuan Chunfa (2001). A Model for 
Processing Temporal References in Chinese. Proceedings of the ACL 
2001 Workshop Temporal and Spatial Information Processing, 33-40. 
Association for Computational Linguistics.

29. Setzer Andrea, Gaizauskas Robert and Hepple Mark (2003). 
Using Semantic Inference for Temporal Annotation Comparison. 
Proceedings of the Fourth International Workshop on Inference in 
Computational Semantics (ICOS-4), 185-196. 

ABOUT THE REVIEWER

Anil Kumar Singh is working towards PhD in Computational Linguistics 
at the Language Technology Research Centre (LTRC), IIIT, 
Hyderabad, India. His research interests are in dealing with temporal 
information in NL, statistical NLP, corpus linguistics and, last but not 
the least, NL engineering. But there is much more to life than research 
interests.





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