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Báo cáo khoa học: DETERMINISTIC PARSING AND UNBOUNDED DEPENDENCIES
This paper assesses two new approaches to deterministic parsing with respect to the analysis of unbounded dependencies (UDs). UDs in English are highly locally (and often globally) ambiguous. Several researchers have argued that the difficulty of UDs undermines the programme of deterministic parsing. However, their conclusion is based on critiques of various versions of the Marcus parser which represents only one of many possible approaches to deterministic parsing. We examine the predictions made by a LR(1) deterministic parser and the Lexicat deterministic parser concerning the analysis of UDs. The LR(1) technique is powerful enough to resolve the local ambiguities we...
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Báo cáo khoa học: DECLARATIVE k VIEV NOOEL FOR DEPENDENCY PARSING INTO BLACKBOARD METHOOOLOGY
Recently, we have augmented the dependency parsing model t o c o v e r a l s o tong-distance dependencies. According to the augmented model we have implemented a blackboard-based dependency p a r s e r ADP (Augmented Dependency P a r s e r ) .
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Báo cáo khoa học: A Comparison of Rule-Invocation Strategies in Context-Free Chart Parsing
Currently several grammatical formalisms converge towards being declarative and towards utilizing context-free phrase-structure grammar as a backbone, e.g. L F G and PATR-II. Typically the processing of these formalisms is organized within a chart-parsing framework. The declarative character of the formalisms makes it important to decide upon an overall optimal control strategy on the part of the processor. In particular, this brings the ruleinvocation strategy into criticalfocus: to gain maximal processing efficiency, one has to determine the best way of putting the rules to use. The aim of this paper is to provide a survey and a practical comparison...
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Báo cáo khoa học: COPING WITH DYNAMIC SYNTACTIC STRATEGIES: AN EXPERIMENTAL ENVIRONMENT FOR AN EXPERIMENTAL PARSER
It includses a n u m b e r of specialized tools t h a t consent an easy, graphics-based interaction with the parser. It is shown in particular how a combination of the characteristics of the parser (based on the lexicon a n d on dynamic unification) and of the e n v i r o n m e n t allow a nonspecialized user to explore heuristics t h a t m a y alter the basica control of the system. In this way, for instance, a p s y c h o l i n g...
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Báo cáo khoa học: Acquisition of Conceptual Data Models from Natural Language Descriptions
Acquiring information systems specifications from natural language description is presented as a problem class that requires a different treatment of semantics when compared with other applied NL systems such as database and operating system interfaces. Within this problem class, the specific task of obtaining explicit conceptual data models from natural language text or dialogue is being investigated. The knowledge brought to bear on this task is classified into syntactic, semantic and systems analysis knowledge. Investigations with a simple syntactic parse and with a semantic analysis using McCorcl's Slot Grammar are reported, and the structure of the systems analysis knowledge...
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Báo cáo khoa học: A STRUCTURED REPRESENTATION OF WORD-SENSESIR OR SEMANTIC ANALYSIS
A framework for a structured representation of semantic knowledge (e.g. word-senses) has been defined at the IBM Scientific Center of Roma, as part of a project on Italian Text Understanding. This representation, based on the conceptual graphs formalism [SOW84], expresses deep knowledge (pragmatic) on word-senses. The knowledge base data structure is such as to provide easy access by the semantic verification algorithm. This paper discusses some important problem related to the definition of a semantic knowledge base, as depth versus generality, hierarchical ordering of concept types, etc., and describes the solutions adopted within the text understanding project. ...
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Báo cáo khoa học: SITUATIONS AND PREPOSITIONAL PHRASES
This paper presents a format for representing the linguistic form of utterances, called situation schemata, which is rooted in the situation semantics of Barwise and Perry. A treatment of locative prepositional phrases is given, thus illustrating the generation of the situation schemata and their interpretation in situation semantics.
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Báo cáo khoa học: TEMPORAL REASONING IN NATURAL LANGUAGE UNDERSTANDING: THE TEMPORAL STRUCTURE OF THE NARRATIVE
This p a p e r proposes a new framework for discourse analysis, in the spirit of Grosz and Sidner (1986), Webber (1987a,b) but differentiated with respect to the type or genre of discourse. It is argued t h a t different genres call for different representations and processing strategies; particularly i m p o r t a n t is the distinction between subjective, pefformative discourse and objective discourse, of which narrative is a primary example. This p a p e r concentrates on narratives and introduces the notions of temporal focus (proposed also in Webber (1987b)) and...
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Báo cáo khoa học: ITERATION, HABITUALITY AND VERB FORM SEMANTICS
It is argued t h a t different genres call for different representations and processing strategies; particularly i m p o r t a n t is the distinction between subjective, pefformative discourse and objective discourse, of which narrative is a primary example. This p a p e r concentrates on narratives and introduces the notions of temporal focus (proposed also in Webber (1987b)) and narrative move.
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Báo cáo khoa học: INTEGRATING SEMANTICS KNO FLEXIBLE SYNTAX BY EXPLOITING ISONORPHISM BETWEEN GRAIElATICAL AND SEMANTICAL RELATIONS
If we want to avoid the use of a full male grammar, the syntactic processes necessary to support the semantic module must be implemented by special dedicated procedures. This paper describe the .solutions used in a semantic analyser of French called SABA, developed at the Computer Sciences department of University of Liege, Belgium.
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Báo cáo khoa học: FRAGMENTATION AND PART OF SPEECH DISAMBIGUATION
That at least some syntax is necessary to support semantic processing is fairly obvious. To know exactly how much syntax is needed, however, and how and when to apply it, is still an open and crucial, albeit old, question. This paper discusses the solutions used in a semantic analyser of French called SABA, developed at the University of Liege, Belgium. Specifically, we shall argue in favor of the usefulness of two syntactic processes: fragmentation, which can he interleaved with semantic processing, and part-of-speech disambiguation, which can be performed as a preprocesslng step. ...
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Báo cáo khoa học: FINITE STATE PROCESSING OF TONE SYSTEMS
It is suggested in this paper that t w o - l e v e l morphology theory (Kay, Koskenniemi) can be extended to include morphological tone. This extension treats phonological features as I/O tapes for Finite State Transducers in a parallel sequential incrementation (PSI) architecture; phonological processes (e.g. assimilation) are seen as variants of an elementary unification operation over feature tapes (linear unification phonology, LUP). The phenomena analysed are tone terracing with tone-spreading (horizontal assimilation), downstep, upstep, downdrift, upsweep in two West African languages, Tem (Togo) and Baule (C6te d'Ivoire). ...
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Báo cáo khoa học: REPRESENTATION OF FEATURE SYSTEMS IN A NON-CONNECTIONIST MOLECULAR MACHINE
This paper is part of an enterprise whose aim is to represent linguistic knowledge in the form of a m o l e c u l a r machine (a dynamic network). That is, the molecules of the network not only store, but also send, receive, and process information. It is claimed that such a network can be conceived of as a model of the coalition structure of a connectionist network. The paper describes how the class of feature systems called unary feature h i e r a r c h i e s (whose importance is supported by...
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Báo cáo khoa học: SOME REASON ON CASE RELATIONS
The topic of the paper is the problem how to define case relations by semantic predicates. A general principle is outlined, which renders it possible to calculate case relations for a given representation of a (verb-)sememe by means of expressions. This principle is based on an assignment of case relations to primitive predicates and modification rules for nested expressions. Contrary to the traditional case grammar it turns out ~ha~ one needs mixed case relations, especially for two reasons: Arguments occur at too different places in an expression or arguments ~iave combined case relations. The consequence is that case relations...
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Báo cáo khoa học: PASSIVES
The English passive construction has played a central role in the to-ings and fro-ings of grammatical theory over the last 30 years, from the earliest days of transformational grammar, to more recent, surface oriented theories of syntax. The casual reader of the linguistic literature might therefore suppose that the computational linguist looking for an off the shelf analysis of passives would be able to choose from among several competing analyses, each of which accommodated the facts, but perhaps derived them from (or from them} different theoretical principles. Unfortunately, this is not the case. as we shall see. All of...
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Báo cáo khoa học: DEALING WITH THE NOTION OBLIGATORY IN SYNTACTIC ANALYSIS
It is easy to see that the tree property would be destroyed if these connections w e r e i n c l u d e d as edges in the tree. To save the t r e e property Kunze introduced the mechanism of paths of action for t h e p a r a d i g m a t i c and s e l e c t i v e connections.
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Báo cáo khoa học: Association for Computational Linguistics
This volume contains texts of the papers presented at the Fourth Conference of the European Chapter of the Association for Computational Linguistics, reserve papers, and tutorial abstracts. Over 130 papers were submitted for the conference, and the overall standard was high: it was with regret and difficulty that the Programme Committee were able to accept only 45, even including parallel sessions and reserve papers. We are grateful to all those who submitted papers, to the Programme Committee and referees for reading them, and to all who worked hard on local arrangements. ...
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Báo cáo khoa học: Parsing Idioms in Lexicalized TAGs
We show how idioms can be parsed in lexiealized TAGs. We rely on extensive studies of frozen phrases pursued at L.A.D.L) that show that idioms are pervasive in natural language and obey, generally speaking, the same morphological and syntactical patterns as 'free' structures. By idiom we mean a structure in which some items are lexically frozen and have a semantics that is not compositional. We thus consider idioms of different syntactic categories : NP, S, adverbials, compound prepositions.., in both English and French. In lexicalized TAGs, the same grammar is used for idioms as for 'free' sentences. We assign...
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Báo cáo khoa học: PARSING AND DERIVATIONAL EQUIVALENCE
It is a tacit assumption of m u c h linguistic inquiry that all distinct derivations of a string should assign distinct meanings. But despite the tidiness of such derivational uniqueness, there seems to be no a priori reason to assume that a g r a m m a r must have this property. If a grammar exhibits derivational equivalence, whereby distinct derivations of a string assign the same meanings, naive exhaustive search for all derivations will be redundant, and quite possibly intractable. In this paper we show how notions of derivation-reduction and normal form can be used to...
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Báo cáo khoa học: EFFICIENT PROCESSING OF FLEXIBLE CATEGORIAL GRAMMAR
From a processing point of view, however, flexible categorial systems are problematic, since they introduce spurious ambiguity. In this paper, we present a flexible categorial grammar which makes extensive use of the product-operator, first introduced by Lambek (1958). The grammar has the property that for every reading of a sentence, a strictly left-branching derivation can be given. This leads to the definition of a subset of the grammar, for which the spurious ambiguity problem does not arise and efficient processing is possible. ...
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Báo cáo khoa học: Dialog Control in a Natural Language System
A considerable amount of work in current AI research is concerned with inferring intentions from utterances (e.g., [Allen 83], [Carberry 83], [Grosz, Sidner 86]) or planning speech acts serving certain goals (e.g., [Appelt 85]), but only a few uniform approaches to both aspects have been presented. Most approaches to dialog control described in the literature offer either rigid action schemata that enable the simulation of the desired behavior on the surface (but lack the necessary degree of flexibility, e. g., [Metzing 79]), or descriptive methods which may also include possible alternatives for the continuation of the dialog, but...
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Báo cáo khoa học: A METAPLAN MODEL FOR PROBLEM-SOLVING
The structure of problem-solving discourse in the expert advising setting can be modeled by adding a layer of metaplans to a plan-based model of the task domain. Classes of metaplans are introduced to model both the agent's gradual refinement and instantiation of a domain plan for a task and the space of possible queries about preconditions or fillers for open variable slots that can be motivated by the exploration of particular classes of domain plans. This metaplan structure can be used to track an agent's problem-solving progress and to predict at each point likely follow-on queries based on related...
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Báo cáo khoa học: TENSES AS ANAPHORA
A proposal to deal with French tenses in the framework of Discourse Representation Theory is presented, as it has been implemented for a fragment at the IMS. It is based on the theory of tenses of H. Kamp and Ch. Rohrer. Instead of using operators to express the meaning of the tenses the Reichenbachian point of view is adopted and refined such that the impact of the tenses with respect to the meaning of the text is understood as contribution to the integration of the events of a sentence in the event structure of the preceeding text. ...
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Báo cáo khoa học: ON THE GENERATIVE POWER OF TWO LEVEL MORPHOLOGICAL RULES
Koskenniemi's model of two-level morphology has been very influential in recent years, but definitions of the formalism have generally been phrased in terms of a compilation (sometimes left unspecified) into a form of finite-state transducers, or else have consisted of an informal outline of the intended interpretation of the rule-formalism itself. Analyses of the properties of the formalism have generally focussed on the transducer mechanism. It is, however, possible to give a fully formal definition of the original rule notation directly, in a way which reflects Koskenniemi's original informal characterisation and which does not depend directly on the...
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Báo cáo khoa học: PARADIGMATIC MORPHOLOGY
We present a notation for the declarative statement of morphological relationships and lexieal rules, based on the traditional notion of Word and Paradigm (cf Hockett 1954). The phenomenon of blocking arises from a generalized version of Kiparsky's (1973) Elsewhere Condition, stated in terms of ordering by subsumption over paradigms. Orthographic constraints on morphemic alternation are described by means of string equations (Siekmann 1975). We indicate some criticisms to be made of our approach from both linguistic and computational perspectives and relate our approach to others such as Finite-State Morphology (Koskenniemi 1983), DATR (Gazdar and Evans 1989) and object-oriented morphophonemics...
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Báo cáo khoa học: Inference in DATR
DATR is a declarative language for representing a restricted class of inheritance networks, permitting both multiple and default inheritance. The principal intended area of application is the representation of lexical entries for natural language processing, and we use examples from this domain throughout. In this paper we present the syntax and inference mechanisms for the language. The goal of the DATR enterprise is the design of a simple language that (i) has the necessary expressive power to encode the lexical entries presupposed by contemporary work in the unification grammar tradition, (ii) can express all the evident generalizations about such...
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Báo cáo khoa học: Ambiguity Resolution in the DMTRANS PLUS
We present a cost-based (or energy-based) model of disambiguation. When a sentence is ambiguous, a parse with the least cost is chosen from among multiple hypotheses. Each hypothesis is assigned a cost which is added when: (1) a new instance is created to satisfy reference success, (2) links between instances are created or removed to satisfy constraints on concept sequences, and (3) a concept node with insufficient priming is used for further processing. This method of ambiguity resolution is implemented in DMT~NS PLUS, which is a second generation bi-direetional English/Japanese machine translation system based on a massively parallel spreading...
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Báo cáo khoa học: THE ORGANIZATION OF THE ROSETTA GRAMMARS
In this paper the organization of the grammars in the Rosetta machine translation system is described and it is shown how this organization makes it possible to translate between words of different syntactic categories in a systematic way. It is also shown how the organization chosen makes it possible to translate 'small clauses' into full clauses and vice versa. The central concept worked out here in some detail is the concept of 'partial isom o r p h y ' between subgrammars. The system as described here has been implemented and is currently being tested. and a control...
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Báo cáo khoa học: Programming in Logic with Constraints for Natural Language Processing
In this paper, we present a logic-based computational model for movement theory in Government and Binding Theory. For that purpose, we have designed a language called DISLOG. DISLOG stands for programming in logic with discontinuities and permits to express in a simple, concise and declarative way relations or constraints between non-contiguous elements in a structure. DISLOG is also weel adapted to model other types of linguistic phenomena like Quantifier Raising involving long-distance relations or constraints. ...
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Báo cáo khoa học: JPSG Parser on Constraint Logic Programming
Prolog is frequently used in implementing natural language parsers or generators based on unification based grammars. This is because Prolog is also based on unification, and therefore has a declarative feature. One important characteristic of unification cu-Prolog adopts constraint unification instead of based grammar is also a declarative grammar formalthe normal Prolog unification. In cu-Prolog, con- ization [11]. However, Prolog does not have sufficient power of straints in terms of user defined predicates can be expressing constraints because it executes every parts directly added to the program clauses. ...
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