Motivation and Goals of the Research

The world of text formatters can be divided into two parts. In one group are the pure formatters, which convert a document description, prepared by a separate editing system, into a formatted document suitable for display on an appropriate hardware device. In the other group are the Integrated Editor/Formatters, which merge the editing and the formatting functions into one unified, interactive system-documents are created, viewed, and revised without leaving the edit or/formatter.

Introduction

Advances in computer technology have brought many new methods of conducting research in typesetting and typography. One area which benefits a lot from the use of modern computers is related to type-font design and evluation. With the aid of a computerized optical scanner, characters in different font styles can be read and converted into digital images. Once these images have been binarized [Suen 1986], they can be stored in matrices and reproduced easily by computers and matrix and laser printers. Hence it is not surprising to see that digital fonts have become more and more widely used in the computer environment. While these binary matrices can be stored and used later for printing, they form a new tool to study several subjects in typography such as legibility of font styles, reading speed/comprehension and font style, spacing of words and texts on the page, line lengths and character sizes. These topics have been of great interest to many psychologists and others (see e.g. Burt 1959, Tinker 1963, Hartley et al 1983). Using modern equipment, these topics can be studied much more rigorously and efficiently than before due to the fact that many parameters such as font styles, character shapes, exposure time, presentation speed, format and spacing, etc.

Presentation

Existing document manipulation systems may be classified into various categories. There are batch formatters [Furuta] and interactive systems [Meyrowitz]. Some formatters such as Scribe [Reid] or Mint [Hibbard] consider the logical structure of the documents they manipulate. Some others, like TEX [Knuth] or Troff [Kernighan], are more concerned with layout, even if macros allow some structure to be introduced in the document.

Formatters have also evolved towards more friendly tools, that allow the user to see quickly on the screen the result of his work: TEX, for example, has several ‘preview’ systems. Janus [Chamberlin] is an original system that has been developed with the same approach. Although they allow the user to see the final form of the document on the screen, these systems cannot be considered as really interactive, as they do not allow the user to interact directly on the final form of the document. Other extensions to formatters have been proposed, by adding a truly interactive editor [André].

Introduction

This paper describes a project within ICL's Office Business Centre that is designing a new document filing and retrieval system. The system is designed to integrate with ICL's networked office product line and to make maximum use of international standards for Open Systems Interconnection. The project is known internally as Textmaster, and an initial subset of the total system is being delivered to selected customers during 1986 under the name ICLFILE.

The system is designed to allow end-users to find the documents they are interested in by means of simple enquiries. They may then view these documents either directly on the screen, or by requesting a printed copy, or by having the document mailed to them electronically. Throughout this process both the typographical layout and the editability of the document are fully preserved. Thus if the user requests a printed copy this can be produced in high quality on a laser printer if required, while if he wishes to edit the document all the necessary layout directives will be preserved. If the document is viewed on the screen it can be presented in a format as close to the printed layout as the screen characteristics will allow: the popular ‘what-you-see-is-what-you-get’ feature of modern word processors.

Introduction

The subject matter of this paper stems from ideas developed in the context of a research contribution made in Lausanne on a document preparation project. The initial goal to produce technical reports has been broadened to solve more general document preparation problems (flexibility, modularity).

As interactive editing systems that include sophisticated typographical features become more fashionable, one might expect traditional formatting techniques to give way. The fact that this is not really the case is due to the advantages and shortcomings inherent in either approach: fast viewing and nice man-machine interface on the WYSIWYG systems, highest typographical quality and greater portability of documents through a variety of textprocessing software on the markup based textfile formatters.

Attempting to combine the good sides of both above mentioned approaches entails several requirements. First, the formatting process needs a flexible parametrisation that provides descriptive formatting specification, clearly separated from the document's content. This approach should offer more flexibility and guarantee portability of a document to several systems with different printing devices. Second, a multi-tasking environment should permit to blend user-comfort with the high typographic quality realized by sophisticated formatting functions.

Introduction

This paper discusses some issues relevant to the design of a Page Description Language (PDL). A PDL is a type of language commonly used for communicating page information from a composition system to an intelligent page printer. These languages are usually specified by the printer manufacturer as an input language, but device-independent outputs from some composition packages, for example DI-TROFF, are also PDLs. I also present a particular PDL, the ACE language, which has been designed by us at Chelgraph and implemented on our Raster Image Processor, the features of ACE itself have been described elsewhere [Chel84, Harris84].

What Is a PDL?

There have always been languages for communicating page information to typesetters and printers. Until recently the capabilities of computer output printers have been very limited, so their input languages have been simple ASCII formats modified by escape codes. Typesetters such as the Autologic APS 5, on the other hand, have quite complex input languages with a syntax and tens of commands.

Introduction

The traditional method of storing information in a printed, linear form as it is done with conventional books has been demonstrated to be inadequate both to represent the complexity of information and to offer quick and flexible access to it [8].

The personal computer appears to be the ideal tool to satisfy these requirements, but a simple computer-based transcription of traditional books is not the best way of taking advantage of the new functionalities offered by computers.

The purpose of this article is to describe one experiment in the design of a documentation system that can take advantage of the flexible data structures and advanced user interface provided by a Smalltalk programming environment.

A semantic network was chosen as the best way of representing the complexity of information ([4],[6]) instead of a more traditional tree structure [5].

In order to understand the relationship between syntactic theory and how people parse sentences, it is first necessary to understand the more general relationship between the grammar and the general cognitive system (GCS). The Chomskyan view, adhered to by most linguists working within the modern generative framework, is that the grammar is a cognitive subsystem whose vocabulary and operations are defined independently of the GCS and account for the structure of language (Chomsky, 1980). Linguistics is thus the branch of theoretical cognitive psychology which explains language structure.

There is another possible relationship between the grammar and the GCS in which linguistics does not play a primary theoretical role in explaining language structure. On this view, the structure of language is explained by basic principles of the GCS – for example, the nature of concepts in interaction with basic properties of the human information processing system. If this view is correct, grammars become convenient organizational frameworks for describing the structure of language. Linguistics is then a descriptive rather than a theoretical branch of cognitive psychology. The linguistics-as-descriptive position was held by the American Structuralists and is presently being revived from a somewhat different perspective in the form of “cognitive grammar” (Lakoff, in press).

These two frameworks for understanding the relationship between grammars and the cognitive system – linguistics as explanation and linguistics as description – suggest different research strategies for answering the question posed by the theme of this book: namely, What is the relationship between syntactic theory and how listeners parse sentences?

There has been some interest in recent years in finding functional explanations for various properties of human languages. The general form of these explanations is

1. Languages have property P because if they did not

2. couldn't learn them; or

3. couldn't plan and produce sentences efficiently; or

4. couldn't understand sentences reliably and efficiently; or

5. wouldn't be able to express the sorts of messages we typically want to express.

Some linguists are dubious about the legitimacy of such investigations, and they are indeed a notoriously risky undertaking. It is all too easy to be seduced by what looks like a plausible explanation for some linguistic phenomenon, but there is really no way of proving that it is the correct explanation, or even that functional considerations are relevant at all. What, then, can be said in favor of this line of research?

Setting aside the sheer fascination of finding answers to why-questions, we can point to some more practical benefits that may result. First, we may find out something about the learning mechanism, or the sentence processing mechanism, or whichever component of the language faculty provides a likely functional explanation for the linguistic facts. In this paper we will concentrate on the sentence parsing mechanism. (See Fodor and Crain, in preparation, for discussion of language learning.) It is clear that one can derive at least some interesting hypotheses about how the parser is structured, by considering how it would have to be structured in order to explain why certain sentences are ungrammatical, why there are constraints excluding certain kinds of ambiguity, and so forth.

Since the late 1970s there has been vigorous activity in constructing highly constrained grammatical systems by eliminating the transformational component either totally or partially. There is increasing recognition of the fact that the entire range of dependencies that transformational grammars in their various incarnations have tried to account for can be captured satisfactorily by classes of rules that are nontransformational and at the same time highly constrained in terms of the classes of grammars and languages they define.

Two types of dependencies are especially important: subcategorization and filler-gap dependencies. Moreover, these dependencies can be unbounded. One of the motivations for transformations was to account for unbounded dependencies. The so-called nontransformational grammars account for the unbounded dependencies in different ways. In a tree adjoining grammar (TAG) unboundedness is achieved by factoring the dependencies and recursion in a novel and linguistically interesting manner. All dependencies are defined on a finite set of basic structures (trees), which are bounded. Unboundedness is then a corollary of a particular composition operation called adjoining. There are thus no unbounded dependencies in a sense.

This factoring of recursion and dependencies is in contrast to transformational grammars (TG), where recursion is defined in the base and the transformations essentially carry out the checking of the dependencies. The phrase linking grammars (PLGs) (Peters and Ritchie, 1982) and the lexical functional grammars (LFGs) (Kaplan and Bresnan, 1983) share this aspect of TGs; that is, recursion builds up a set a structures, some of which are then filtered out by transformations in a TG, by the constraints on linking in a PLG, and by the constraints introduced via the functional structures in an LFG.

In this paper I want to draw together a number of observations bearing on how people interpret constituent questions. The observations concern the interpretation possibilities for “moved” and “unmoved” wh-phrases, as well as wide scope interpretation of quantifiers in embedded sentences. I will argue that languages typically display a correlation between positions that do not allow extractions and positions where a constituent cannot be interpreted with wide scope. Given this correlation, it seems natural to investigate the processes of extraction and wide-scope interpretation from the perspective of sentence processing, in the hope of explaining correlations between the two. I have singled out constituent questions because they illustrate the parsing problem for sentences with nonlocal filler-gap dependencies; they are a particularly interesting case to consider because of interactions between scope determining factors and general interpretive strategies for filler-gap association.

Gap-filling

To what extent is the process of gap-filling sensitive to formal, as opposed to semantic, properties of the linguistic input? One type of evidence that is relevant here is the existence of a morphological dependency between the filler and the environment of the gap, as illustrated in (1).

1. (1) a. Which people did Mary say — were invited to dinner?

2. b. *Which people did Mary say — was invited to dinner?

In languages with productive case marking, a similar type of dependency will hold between the case of the filler and the local environment of the gap. This kind of morphological agreement is typically determined by properties having to do with the surface form of the items in question, or with inherent formal properties, such as which noun class a given noun belongs to.

The ostensive goal of this paper is to construct a general complexity metric for the processing of natural language sentences, focusing on syntactic determinants of complexity in sentence comprehension. The ultimate goal, however, is to determine how the grammars of natural languages respond to different types of syntactic processing complexity.

A complexity metric that accurately predicts the relative complexity of processing different syntactic structures is not, in itself, of much theoretical interest. There does not seem to be any compelling reason for linguistic theory or psycholinguistic theory to incorporate such a metric. Rather, ultimately the correct complexity metric should follow directly as a theorem or consequence of an adequate theory of sentence comprehension.

Different theories of sentence comprehension typically lead to distinct predictions concerning the relative perceptual difficulty of sentences. Hence, one reason for developing a complexity metric is simply to help pinpoint inadequacies of current theories of sentence comprehension and to aid in the evaluation and refinement of those theories. An explicit complexity metric should also help to reveal the relation between the human sentence processor and the grammars of natural languages. In particular, developing a well-motivated complexity metric is a crucial prerequisite for evaluating the hypothesis that the grammars of natural languages are shaped in some respect by the properties of the human sentence processor since the most common form of this hypothesis claims that grammars tend to avoid generating sentences that are extremely difficult to process.

In this paper we describe an experiment in sentence processing which was intended to relate two properties of syntactic structures that have received much discussion in linguistics and psychology (see references cited in the next section). First, some syntactic structures, such as the passive construction, require more processing effort than corresponding structures which express the same grammatical relations. Passive sentences in particular have been the subject of much experimental work. Second, it is clear, as was observed by Jespersen (1924), that the difference between active and passive sentences has something to do with focus of attention on a particular constituent, the grammatical subject. And the consequences of the difference of focus of attention is in some way related to the context formed by the discourse in which the sentence occurs. In this experiment we wanted to study syntactic structures which might have similar properties to the passive/active construction, so as to define exactly what features of passive sentences are responsible for their observed greater processing demands and definition of focus of attention, or sentence topic. One of the bases of the experiment, underlying the hypotheses we wanted to test, is that processing load and definition of sentence topic are related in some way.

We combined sentences exemplifying five different syntactic constructions with context sentences having different relations to the target sentences, and measured reaction time for reading and understanding the second or target sentence. The results show that there is a fairly consistent relationship of processing load for the other constructions as well as passive, and that overall processing time is sensitive to both syntactic structure and contextual information.