corpus-based semantics of concession livio robaldo department of computer science, university of...
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Corpus-based Semantics of Concession
Livio RobaldoDepartment of Computer Science, University of Turin
Eleni MiltsakakiInstitute for Research in Cognitive Science, UPenn
Alessia BianchiniDepartment of Computer Science, University of Turin
The PDTB: Discourse relations• They are conveyed by lexical items connecting two
textual spans.
On the one hand, John loves Barolo.So he went and ordered three cases.On the other hand, he didn’t have much money.So then he had to cancel the order.
Examples:
Discourse relations
John loves Barolo.
On the one hand –On the other hand
So
So
then
he went and ordered three cases.
he didn’t have much money.
he had to cancel the order.
PDTBThe Penn Discourse Treebank is, to date, the largest annotation effort at the discourse level (more than 40000 annotations).
• It encodes discourse relations associated with discourse connectives.
• It includes implicit connectives. E.g.
[John broke his arm]arg1.
(implicit=so) [Now, he can’t cycle to work]arg2
• Annotations are made on the Penn Treebank, including approximately 1 million words, taken from the Wall Street Journal.
Sense annotation in the PDTBSome discourse connectives can be ambiguous and encompass more than one meaning. E.g. since:
Temporal
Since [the first fraud was discovered in July 1986 at an office of the People’s Bank of China]arg2, [15 major cases have been found]arg1.
Causal
[It was a far safer deal for lenders]arg1 since
[NWA had a healthier cash flow and more collateral on hand]arg2.
Aim of the sense annotationThe aim of the annotation of senses is to provide sense tags which will flag the intended interpretation of the connectives.
Identifying senses has proved to be a challenging task. Fine grained or coarse grained distinctions?
Extensive sense annotation studies have been carried out to disambiguate the meaning of verbs (see, for example, Propbank: http://verbs.colorado.edu/~mpalmer/projects/ace.html). Much less for discourse connectives…
Semantic CLASSes
Semantic CLASSes
TEMPORAL CONTINGENCY COMPARISON EXPANSION
Comparison CLASS Types
Comparison
Contrast
juxtaposition
Concession
expectationopposition contra-expectation
ConcessionThe Type Concession applies when:
Arg2 event/state A implies an event/state C but Arg1 event/state B states or implies ~C
ORArg1 event/state A implies an event/state C but Arg2 event/state B states or implies ~C
The former is tagged as ‘expectation’, the latter as ‘counter-expectation’.
Literature on Concession
Direct Contrast:
Although [Greta Garbo was considered the yardstick of beauty]Argc, [she never married]Argd.
In the literature [Winter & Rimon, 94], [Lagerwerf, 98], [Korbayova & Webber, 07], two cases have been distinguished, according to how the expectation is denied: directly or indirectly.
• A general defeasible rule “Beatiful women usually married ” holds in the context. • This rule creates the expectation that Greta Garbo married.• Argd directly denies this expectation, by asserting exactly the opposite.
Literature on Concession
Indirect Contrast:
Although [John does not have a car]Argc, [he has a bike]Argd.
In the literature [Winter & Rimon, 94], [Lagerwerf, 98], [Korbayova & Webber, 07], two cases have been distinguished, according to how the expectation is denied: directly or indirectly.
• The concessive relation involves an intermediate proposition, called the Tertium Comparationis (TC) [Lagerwerf, 98], defeasibly implied by Argc and whose negation is (non-defeasibly) implied by Argd.• In the example below, the TC is “John is not mobile”: Argc defeasibly implies that John is not mobile, while Argd implies that he is mobile.
Logical accounts of Concession
Previous logical accounts of Concession mirror the distinction between Direct and Indirect Contrast.
Direct Contrast:
(p q) ∧ ∧ (p →¬q)
Indirect Contrast:
(p q) r[∧ ∧ ∃ (p →¬r) (q → r)]∧
Previous accounts of ConcessionPrevious approaches to Concession mainly focus on how the expectation is denied (either directly or indirectly).
They are almost silent about how the expectation is created, i.e. on the relation between Argc and the expectation that must be presupposed.
Some [Lagerwerf, 98], [Sanders et al., 92] generally state it is of a causal nature.
We think that characterizing how the relation is created is crucial for defining the semantic of concessive relations. We tried to take a first step starting from an empirical analysis of PDTB data.
Four subcases of Concession
Toy examples:
Causality: Although [John studied hard]argc, [he did not pass the exam]argd.
Implication: [Penguins are birds]argc. Nevertheless [they do not fly]argd
Correlation: [John will write the report]argc but [he'll finish it at home]argd
Implicature: Although [John ate a lot of pizza]argc [he did not eat it all]argd.
Causality: Although [they represent only 2% of the population]argc, [they control nearly one-third of discretionary income]argd.
Implication: [The prime minister]argd [whose hair is thinning and gray and whose face has a perpetual pallor]argc nonetheless [continues to display an energy, a precision of thought and a willingness to say publicly what most other Asian leaders dare say only privately]argd.
Correlation: [The Treasury will raise 10 billion in fresh cash by selling 30 billion of securities...]argc. But [rather than sell new 30-year bonds, the Treasury will issue 10 billion of 29-year, nine-month bonds]argd.
Implicature: Although [it is not the first company to produce the thinner drives]argc, [it is the first with an 80-megabyte drive]argd.
From the PDTB:
Empirical (double) annotation on 1000 PDTB tokens
Inter-annotator agreement k = 0.8
The analysis provides some evidence that the source of expectation is not always a causal relation.
Implication
Although [working for USA intelligence]argc, [Mr. Noriega was hardly helping the U.S. exclusively]argd.
Although [insider trading has long been criminal]argc, [for example it has never been statutorily defined]argd.
[You can do all this]argc even if [you’re not a reporter or a researcher or a scholar or a member of Congress]argd.
Necessary conditions, rather than causal effects, inherited from some kind of prototype.
Correlation
Although [the notes held at a price of 92 to 93 immediately after the reset]argc, [they started falling soon afterward]argd.
Divergence from a contextually relevant trend
[The LDP won by a landslide in the last election, in July 1986]argc. But [less than two years later, the LDP started to crumble, and dissent rose to unprecedented heights]argd.
[Yet the rowing machine hasn't been touched since]argd even though [he has moved it across the country with him twice]argc
Correlation
Although [started in 1965]argc [Wedtech didn’t really get rolling until1975]argd.
Events that “surprisingly” occur together
[The favorite remains Fernando Collor de Mello, a 40-year-old former governor of the state of Alagoas]argc. But […Mr. Collor has slipped to about 30% in the polls from a high of about 43% only a few weeks ago]argd.
[The Journal listed the creation of the money fund as one of the 10 most significant events in the world of finance in the 20th century]argc. But [the Reserve Fund, America’s first money fund, was not named, nor were the creators of the money-fund concept, Harry Brown and myself]argd.
ImplicatureViolation of a Gricean Maxim: Argc is insufficient or unrelevant with respect to the speaker’s intentions.
Although [John ate a lot of pizza]argc [he did not eat it all]argd.
[Open the computer case]argc but [do not touch the wires]argd.
Although [it is not the first company to produce the thinner drives]argc, [it is the first with an 80-megabyte drive]argd.
Thank you!