Alex Lascarides and Nicholas Asher:
Discourse Relations and Common Sense Entailment
This paper presents a formal account of the temporal interpretation of
text. The distinct natural interpretations of texts with similar syntax
is explained in terms of defeasible rules characterising causal laws and
Gricean-style pragmatic maxims. Intuitively compelling patterns of
defeasible entailment that are supported by the logic in which the
theory is expressed are shown to underly temporal interpretation.
(February 1991, 65 pages)
Ref. No: HCRC/RP-16 Price: UKL 2.30
Jerry Seligman:
Physical Situations and Information Flow
In this paper we take Rosenschein's physicalist ontology used in his
work on Situated Automata and use it to construct a number of Situation
Theoretic categories: situations, types and perspectives. In so doing
we replace Rosenschein's notion of information content by a conception
of information based on the idea of an information channel. This
provides a perspectival account of information flow which does not
depend on modal alternatives, like possible worlds. We hope to sharpen
intuitions about situations and information flow by focussing on
``physical'' situations and thereby illuminate the place of
information in the physical world.
(March 1991; 37 pages)
Ref. No: HCRC/RP-17 Price: UKL 1.40
Chris Brew:
Systemic Classification and its Efficiency
This paper examines the problem of classifying linguistic objects on the
basis of information encoded in the system network formalism developed
by Halliday. We show that this problem is NP-hard, and suggest a
restriction to the formalism which renders the classification problem
soluble in polynomial time. We then develop an algorithm for the
unrestricted classification problem, separating a potentially expensive
second stage from a cheaper first stage which is known to be tractable.
(March 1991; 38 pages)
Ref. No: HCRC/RP-18 Price: UKL 1.40
Keith Stenning and Jon Oberlander:
Reasoning with Words, Pictures and Calculi: computation versus
justification
Hyperproof is a system due to Barwise and Etchemendy for teaching
heterogeneous reasoning which allows both graphical and linguistically
defined steps of inference. In this paper we draw a distinction between
the performance as opposed to the justification of inference. The
processes relate to cognitive as opposed to foundational theories of
inference respectively. We argue graphical reasoning does not
necessarily require a novel foundational account but that a cognitive
theory of graphics is required to understand heterogeneous reasoning. We
sketch such an account centered on the property of graphical
representations that they force the specification of much information
which may go beyond the intended message.
(April 1991; 15 pages)
Ref. No: HCRC/RP-19 Price: UKL 1.00
Keith Stenning and Jon Oberlander:
A Cognitive Theory of Graphical and Linguistic Reasoning: Logic and
Implementation
Our main subject is the processing characteristics of external graphical
representations. Our main aim is to argue for the thesis that some of
these characteristics can be explained by the property of specificity.
We take the presence or absence of this property to be independent of
the modality in which information is encoded; it can be present in
linguistic systems, just as in graphical systems. To indicate the
practical ramifications of the thesis, we discuss in detail the use of a
version of Euler's Circles, an external graphical system, in syllogistic
reasoning tasks. In particular, we show that mental models, an
apparently non-graphical system, is equivalent---at one level---to our
graphical system. This vindicates our appraoch to cognitive
representation, which permits the characterisation of the equivalences
and differences between graphical and non-graphical representations.
The equivalences can be captured at a logical level; the differences are
a matter of implementation. The cognitive properties of graphical
representations are best understood in terms of this relationship
between logic and implementation.
(March 1992; 43 pages)
Ref. No: HCRC/RP-20 Price: UKL 1.60
Rosemary J. Stevenson, Rosalind A. Crawley, David Kleinman:
Semantic Constraints on the Comprehension of Definite References
Two experiments are described which investigate the effect of context on
the comprehension of definite references. A distinction is made between
contexts that require the use of bridging inferences and those that are
infelicitous. It is argued that infelicitous contexts affect the
interpretation of noun phrases and pronouns equally while contexts that
require bridging inferences impair the comprehension of pronouns but not
of names.
Ref. No: HCRC/RP-21 Price: UKL 1.00
Jerry Seligman:
A Cut-free Sequent Calculus for Elementary Situated Reasoning
A first-order language is interpreted in the following way: terms are
regarded as referring to situations and the truth of formulae is
relativized to a situation. The language is then extended to include
formulae of the form $t:\phi$ (where $t$ is a term and $\phi$ is a
formula) meaning that $\phi$ is true in the situation referred to by
$t$. Gentzen's sequent calculus for classical first-order logic is
extended with rules which capture this interpretation. Variants of the
calculus and extensions of the language are discussed and the Cut rule
is shown to be eliminable from some of the proposed calculi.
(September 1991; 23 pages)
Ref. No: HCRC/RP-22 Price: UKL 1.10
A J Sanford \& L M Moxey:
Notes on Plural Reference and the Scenario-Mapping Principle in
Comprehension
This paper concerns the way in which plural reference might be handled
within the framework of text comprehension offered by Sanford and Garrod
(1981), and other related accounts. It is motivated by the fact that
there has been relatively little work on the conditions which control
plural reference patterns, and we suggeset an approach to this problem,
based on considerations of focus and mapping of discourse to general
knowledge. We also address a number of critical comments recently made
in which a basic inability of the Sanford-Garrod framework to encompass
plurals is suggested. We suggest that the framework is quite capable of
handling at least some of the problems of plural reference. The basic
argument is that plural reference is licensed if and only if two or more
individuals map into the same role-slot of the memory-representation of
the situation depicted. Complications introduced by questions of
cohesion and focus are discussed. In particular, coherence problems
force a distinction between correct reference resolution in the face of
unsatisfactory discourse, and its acceptability from the standpoint of
felicity. It is concluded that this approach does not require arbitrary
rules for when plural anaphors can be used, and that it provides a
natural solution for mechanisms of grouping.
(October 1991; 19 pages)
Ref. No: HCRC/RP-23 Price: UKL 1.10
Robin Cooper:
A Working Person's Guide to Situation Theory
This is meant to provide an informal introduction to naive situation
theory which will be useful to a working linguist or a cognitive
scientist who wishes to apply the theory. It may also be of interest
to some situation theorists. We use Extended Kamp Notation ({\sc
ekn) as developed in Barwise and Cooper (forthcoming) as well as
introducing the basic elements of the standard linear notation which
is to be found in the literature on situation theory and situation
semantics. {\sc ekn is so called because it takes its inspiration
from the notation that is used by Kamp in developing Discourse
Representation Theory ({\sc drt).
(October 1991; 27 pages)
Ref. No: HCRC/RP-24 Price: UKL 1.20
Anne H. Anderson and Elizabeth H. Boyle:
Forms of Introduction in Dialogues: Their Discourse Contexts and
Communicative Goals
For effective communication to occur, speakers must share enough
knowledge to understand one another's contributions: they must achieve
`mutual knowledge'. A criticial point in a dialogue is therefore when
one speaker wishes to introduce a new item. We explore the forms of
introduction used by adult speakers in task-oriented dialogues. In
previous studies researchers have concentrated on how indefinite and
defintie articles are used to signal the speaker's assumptions about her
hearer's knowledge state, and hence ability to understand a reference to
a newly introduced topic. From studying a corpus of comparable
dialogues we identify a range of forms of introduction---questions and
statements containing definite or indefinite articles which are used by
speakers. By studying the discourse contexts in which these various
forms occur, and the success of the communication in which they are
embedded, we identify a number of different factors which predict which
forms of introduction will be chosen and the probably communicative
consequences of the selections made. The choice of question forms of
introduction was found to be a more salient aspect of the communicative
process than the choice of article.
(December 1991; 38 pages)
Ref. No: HCRC/RP-25 Price: UKL 1.40
Keith Stenning, Alexander W.R. Nelson, Mukesh J. Patel, Joe Levy, Martin Gemell:
Three Experiments Investigating Reference Change in Simple Descriptions
Stenning, Shepherd and Levy (1988) showed that when simple texts switch
reference predictably between individuals, changes of reference neither
cost reading time nor degrade memory performance. The present
experiments examine the effects of unpredictable referential change.
Experiment 1 demonstrates that unpredictable reference change does cost
processing time, as a function of the amount known about the referent to
which attention shifts. Analysis reveals a distinction between {\em
primary and secondary individuals related to referential change. It also
reveals word length effects, both decelerations and accelerations
proportional to description length, which are interpreted in terms of
use of the articulatory loop (Baddeley, 1986). Experiment 2 replicates
and extends Experiment 1. It extends observations of the involvement of
primary/secondary status in the process of switching reference, and
shows that the word length effects cannot be interpreted in terms of
frequency. Experiment 3 strengthens support for the primary/secondary
distinction and confirms the use of the articulatory loop. The present
results suggest a central role for distributed information about
sequence in representing complex semantic structures both in immediate
and in long term memory. Predictable switching costs no time because
the transparency of the relation between surface sequence and underlying
semantic structure is preserved. The distinction between primary and
secondary individuals emerges with unpredictable reference because it
restores this transparency.
(December 1991; 38 pages)
Ref. No: HCRC/RP-26 Price: UKL 1.40