Alistair Knott

Anaphora and Discourse Structure

We argue in this article that many common adverbial phrases generally taken to signal a discourse relation between syntactically connected units within discourse structure instead work anaphorically to contribute relational meaning, with only indirect dependence on discourse structure. This allows a simpler discourse structure to provide scaffolding for compositional semantics and reveals multiple ways in which the relational meaning conveyed by adverbial connectives can interact with that associated with discourse structure. We conclude by sketching out a lexicalized grammar for discourse that facilitates discourse interpretation as a product of compositional rules, anaphor resolution, and inference.

Using linguistic phenomena to motivate a set of coherence relations

The notion that a text is coherent in virtue of the “relations” that hold between the elements of that text has become fairly common currency, both in the study of discourse coherence and in the field of text generation. The set of relations proposed in Rhetorical Structure Theory (Mann & Thompson, 1987) has had particular influence in both of these fields. But the widespread adoption of “relational” terminology belies a certain amount of confusion about the relational constructs themselves: No two theorists use exactly the same set of relations, and often there seems no motivation for introducing a new relation beyond considerations of descriptive adequacy or engineering expedience. To alleviate this confusion, it is useful to think of relations not just as constructs with descriptive or operational utility, but as constructs with psychological reality, modelling real cognitive processes in readers and writers. This conception of coherence relations suggests a methodology for delineating a set of relatio...

ILEX: an architecture for a dynamic hypertext generation system

Generating text in a hypermedia environment places different demands on a text generation system than occurs in non-interactive environments. This paper describes some of these demands, then shows how the architecture of one text generation system, ILEX, has been shaped by them. The architecture is described in terms of the levels of linguistic representation used, and the processes which map between them. Particular attention is paid to the processes of content selection and text structuring.

Conversation in the museum: experiments in dynamic hypermedia with the intelligent labelling explorer

We outline experience with the Intelligent Labelling Explorer, a dynamic hypertext system developed at the University of Edinburgh, in collaboration with the National Museums of Scotland. First, we indicate a number of ways in which labels on museum objects ought to be tuned to take into account types of visit, the interests of visitors, and their evolving knowledge during a visit. Secondly, we sketch the general architecture of our system, and then focus on the conversational effects which the system can create. We then briefly indicate future directions of research, before critically discussing the applicability (or otherwise) of the spatial metaphor to flexible hypertexts.

Interpreting pronouns and connectives: Interactions among focusing, thematic roles and coherence relations

This paper investigates the relationship between focusing and coherence relations in pronoun comprehension. In their focusing model of pronoun comprehension, Stevenson, Crawley and Kleinman (1994) proposed a default focus on the thematic role associated with the consequences of a described event, a focus that may be modified by the attention-directing properties of a subsequent connective. In this paper we examine a second function of connectives: that of signalling the coherence relations between two clauses (e.g., a NARRATIVE relation or a RESULT relation). In three studies, we identified the coherence relations between sentence fragments ending in pronouns and participants’ continuations to the fragments. We then examined the relationship between the coherence relation, the preferred referent of the pronoun and the referent’s thematic role. The results of studies 1 and 2 showed that people aim to keep the focused entity, the coherence relation and the referent of the pronoun in alignment. Study 3 included the connective next, which enabled us to generate different predictions for the roles of focusing and coherence relations in pronoun resolution. The results favoured the focusing view. The preferred referent of the pronoun was the focused, first mentioned, individual, whereas the coherence relation was consistent with the thematic role of the pronominal referent. If the pronoun referred to an Agent, a NARRATIVE relation was preferred, if the pronoun referred to a Patient, a RESULT relation was preferred. Discussion of these and other results led to the following conclusions. First, pronoun resolution is primarily determined by focusing, either semantic or structural, although a range of other features, including coherence relations and verb semantics, may also act as pressures on pronoun resolution. Second, the consistent link we observed between thematic roles and coherence relations may provide a mapping between a represented entity and a represented event. Third, the connectives we used have three distinct functions: an attention directing function, a function for constraining the possible coherence relation between two events, and a function for interpreting a clause as having either a causal or a temporal structure.

Discourse Relations: A Structural and Presuppositional Account Using Lexicalised TAG

We show that discourse structure need not bear the full burden of conveying discourse relations by showing that many of them can be explained nonstructurally in terms of the grounding of anaphoric presuppositions (Van der Sandt, 1992). This simplifies discourse structure, while still allowing the realisation of a full range of discourse relations. This is achieved using the same semantic machinery used in deriving clause-level semantics.

A feature-based account of the relations signalled by sentence and clause connectives

This paper describes a three-stage methodology for investigating the semantics and pragmatics of sentence and clause connective phrases. The first step in the methodology is to assemble a large corpus of connectives. The second step is to organize this corpus into a hierarchical taxonomy of synonyms and hyponyms, using a pre-theoretical substitution test. The final step, upon which we concentrate in this paper, is to impose a theoretical interpretation on the taxonomy. The taxonomy lends itself to an analysis of intersentential / interclausal relations in terms of a number of orthogonal multivalued features; connectives are then seen as signaling the values of one or more of these features.

Multiple Discourse Connectives in a Lexicalized Grammar For Discourse

Lexicalized grammars1 such as TAG (Joshi, 1987; XTAG-Group, 1998) and CCG (Steedman, 1996) have been very successful in showing how clauselevel syntax and semantics project from the lexicon. What drives the current enterprise is the hypothesis that the same can be shown true, at some level, for discourse syntax and semantics. Here we demonstrate our initial effort to — extend a lexicalized grammar (LTAG) to discourse; — use the same compositional semantics on syntactic structure that is used in lexicalized grammars (Steedman, 1996; Stone and Doran, 1997; Stone and Webber, 1998; Joshi and Vijay-Shanker, 1999); — extend to discourse connectives the idea that the meaning of a lexical element can involve an anaphoric link to the previous discourse; — exploit similar inference mechanisms for defeasible aspects of both sentence-level and discourse semantics.

Integrating natural language generation and hypertext to produce dynamic documents

Abstract We discuss a task requiring the coherent presentation of heterogeneous information about objects recorded in electronic catalogues. We consider the advantages of combining hypermedia delivery with natural language generation technology, so as to allow us to view a session with such a system as a coherent conversation or dialogue. We describe two prototype systems we have built which make use of these combined techniques, and focus on those aspects of the systems which attempt to provide coherence. Although the techniques themselves are not novel, their combination is relatively recent, and promises to help forge useful tools for accomplishing our specific information retrieval task.

Mapping sensorimotor sequences to word sequences: a connectionist model of language acquisition and sentence generation.

In this article we present a neural network model of sentence generation. The network has both technical and conceptual innovations. Its main technical novelty is in its semantic representations: the messages which form the input to the network are structured as sequences, so that message elements are delivered to the network one at a time. Rather than learning to linearise a static semantic representation as a sequence of words, our network rehearses a sequence of semantic signals, and learns to generate words from selected signals. Conceptually, the networks use of rehearsed sequences of semantic signals is motivated by work in embodied cognition, which posits that the structure of semantic representations has its origin in the serial structure of sensorimotor processing. The rich sequential structure of the networks semantic inputs also allows it to incorporate certain Chomskyan ideas about innate syntactic knowledge and parameter-setting, as well as a more empiricist account of the acquisition of idiomatic syntactic constructions.