In this section we discuss approaches to fragments that do not have direct counterparts in the literature onVPE.18 They are not discourse-based in the same sense as above in Section 3.4, but rather emphasise the importance of pragmatic reasoning on the resolution of fragments. They both use the notion of intention as a starting point, (Barton 1990) using an explicitly Gricean approach and trying to make the notion of conversational maxims fruitful for this application, whereas (Carberry 1990) takes a more direct approach in recovering intentions behind utterances.
17It is not clear to us from the presentation in (Alshawi 1992) what exactly the impact ofp=vpis in this representation. It cannot be meant to restrictPto values that are representations of VPs; they themselves later give an example where the short-answer fills an object-position, and hence where the property is not a VP.
18Although cf. (Kuno 1987), where informal pragmatic constraints onVPEare stated.
4.4.1 Barton (1990)
As already briefly mentioned above in Section 2.4, (Barton 1990) makes an interesting distinction of the phenomenon of fragments which resembles ours between res-via-id and res-via-inf. Barton motivates this distinction with data like the following:
(157) a. A: What stops the White House staff from visiting Tip O’Neill in his Congressional of-fice?
B: (An) old grudge.
b. A: The White House staff doesn’t visit Tip O’Neill in his Congressional Office.
B: Old Grudge.
Data like (157-b) is explicitly offered as evidence against Morgan’s (1973) ellipsis approach, with the argumentation we described above, namely that in these examples there is no explicit reconstruc-tion/deletion trigger. As Barton similarly only sees the two alternatives for analysis of fragments offered by Morgan and described above, she hence argues for base generation and direct interpretation. Again, we are not much interested in the syntactic arguments for base generation, and so we concentrate on her arguments for and her explication of aDIT.19
According to (Barton 1990), the data motivates the postulation of two distinct modules of interpretation, one of linguistic context, responsible for the resolution of fragments like (157-a), and one of conver-sation context, in which fragments like (157-b) are resolved. We turn to the former first. In Barton’s model, utterances are represented in the ‘linguistic context’ in the form of what roughly corresponds to (syntactic) logical form annotated with thematic roles / argument structure, as shown in (158-b) for the first sentence of exchange (158-a).
(158) a. A: Mitchell gave a sworn statement, didn’t he?
B: Yes, sir. To the Jury.
b. [S[NPMitchell] [V gave] [NPa sworn statement] ], . . .
SOURCE [SRC,PATIENT, (GOAL)]PATIENT
In the ‘module of linguistic context’ now, fragments or ‘independent constituent utterances’, as she calls them, are resolved through an operation of discourse inference, which starts from a question about intentions of the speaker:
“[W]hat hearers do is draw inferences about the intentions of a speaker with respect to fitting an independent constituent utterances into this structure of linguistic context.” (Barton 1990, p.142)
“If a discourse sequence includes an independent constituent utterance that potentially matches an
19Moreover, much of the book is concerned with (Chomskian) syntactic theory specific considerations of the autonomy of linguistic modules, which do not concern us here. We will later use a mono-stratal linguistic theory which does not have such problems.
expansion possibility of a previous element within the structure of linguistic context, then assign the constituent utterance to function as that expansion possibility in an elaboration of the structure of linguistic context.” (p.112)
The ‘expansion possibility’ is defined there as ‘the ability of a lexical item to select an argument role or to occur with a modifier.’ This operation would resolve the fragment ‘to the jury’ in (158-a) above to fill the thematic roleGOAL, as shown in the following.
(159) [S[NPMitchell] [V gave] [NPa sworn statement] ], didn’t he?
SOURCE [SRC,PATIENT, (GOAL)]PATIENT
[PP[Pto] [NPthe Jury] ]
GOAL
Barton (1990) does not further specify how such resolved fragments are interpreted, i.e. she does not offer a formal semantics of such constructs. However, with some goodwill, this part of the approach can be understood as a semantic approach as in the previous section, extended with a representation for optional elements. In any case it offers the interesting observation that fragments can also ‘add’ optional complements; as shown in Chapter 2.
The module of conversational context on the other hand is based on the notion of cooperative contribu-tion, following (Grice 1969). Fragments like the one in (157-b)—in general, our res-via-inf fragments—
are resolved in Barton’s approach through an operation of ‘cooperative inference’, via reasoning about their relevance:
“In a discourse sequence, the representation of linguistic context for each utterance becomes the representation of an utterance with a potential structure of implicatures explaining its relevance as a cooperative contribution within the conversational context.” (Barton 1990, p.166)
The principle of relevance, however, is notoriously difficult to formalise (but see (Sperber & Wilson 1986)), and Barton does not offer much in this direction, apart from a classification into ‘domains of relevance’:
(160) Types of Cooperative Inference, according to (Barton 1990, p.167):
a. information from knowledge of the physical context of the situation b. knowledge of the topic of conversation
c. background knowledge of interlocutors d. knowledge of the world
Insofar as the theory of discourse in which we realize our resolution mechanism (SDRT) realizes the idea of relevance, our approach can be seen as related to this. However, as will be discussed below,SDRT
crucially denies that reasoning about intentions is always the starting point for discourse inference;
rather it places linguistic and discourse information on the same level.
4.4.2 Carberry (1990)
Another interesting pragmatics-based approach is offered by (Carberry 1989, Carberry 1990).20 In this approach, resolution of fragments is based on recovering the intentions and plans of dialogue parti-cipants, and seeing how the fragment might further such plans. Carberry claims that
“understanding intersentential ellipsis often depends more on pragmatic knowledge, such as the in-ferred task-related plan and discourse goals motivating the speaker, than on the syntactic structure or semantic content of the preceding utterances” (Carberry 1989, p.76)
As support for this view, she gives the following example:
(161) A: I want to cash this check.
Small bills only, please.
For examples like (161), we do not disagree with the claim that reasoning about plans is important to resolve the fragment. In fact, as the reader will recall, we also have in our taxonomy in Chapter 2 speech act types that are individuated with reference to plans. What we disagree with is the claim that one always has to reason about intentions when resolving fragments.21 We claim that there is a large class of fragments where such plan-based reasoning can be avoided: for example short-answers, or elaborations. Moreover, there seems to be no room for linguistic structures like discourse structure in Carberry’s model, whereas (Moore & Pollack 1992) show that this information is equally important.
The following example (repeated from Chapter1) illustrates this:
(162) Peter: Let’s meet the weekend after next.
Mary: OK, but not Saturday.
Peter: Right. #2pm?
If only goals are recorded, the model cannot predict that the last utterance in this example is infelicitous;
it cannot mean “how about we meet at 2pm on Sunday?”, even though meeting on Sunday can be assumed to be the goal at that point. A plan-based approach restricts the flow of information too much, in that it always puts intentions at the beginning of the process of computing implicatures. Following
SDRT, we think this model is not general enough.22
20We have already discussed her taxonomy of fragments above in Section 2.4.
21Even though the statement quoted above is qualified with ‘often’, Carberry does not show how her model would make use of other knowledge sources, and it is not clear whether she suggest that only other kinds of ellipsis (e.g.VPE) can be resolved using ‘syntactic structure or semantic content of the preceding utterances’, or some kinds of fragments as well. In any case, her algorithm always begins with inferring intentions, and that is what we are arguing against here.
22(Fern´andez & Ginzburg 2002) also argue against Carberry on the grounds that such complex reasoning does not always seem to be required. However, as we will argue in the next chapter, their approach does not seem to be capable of ever allowing it. We simply want to argue for a more flexible set-up where information can flow either way.
Moreover, there is amassing psycho-linguistic evidence that costly reasoning about intentions is only the last resort in dialogue processing, and if there are cheaper ways of interpreting material then they are chosen (Pickering & Garrod in press). However, we do not argue systematically for psycholinguistic plausibility of our model.
Lastly, we disagree on what the task of fragment resolution is. This can be illustrated with the following examples from (Carberry 1989). Carberry contrasts these dialogues to show that information about shared beliefs is needed to resolve fragments. In (163), the fragmental question “at night?” is used to express surprise, according to Carberry, whereas it is simply used to enquire about more details in (164).
This difference arises from the fact that the queried information is already mutually known in the former dialogue, but not in the latter.
(163) A: When does CS400 meet?
B: CS400 meets on Monday from 7:00pm until 9:00 pm.
A: Who’s teaching it?
B: Dr. Brown.
A: At night?
(164) A: Who’s teaching CS400?
B: Dr. Brown.
A: At night?
While we do not dispute that these two utterances carry different implications, we do not want to model these directly in the resolution of the fragment. In our approach, the question will in both cases resolve to something paraphraseable as “is Dr. Brown teaching this course at night?”; additional implicatures might then be computed on the basis of this. Our (more modest) goal is simply to predict the truth conditional content of fragments, including the (truth conditional) resolution of the underspecified bits.