3203844
Some Novel Applications of Explanation-Based Learning for Parsing Lexicalized Tree-Adjoining Grammars
In this paper we present some novel applications of Explanation-Based Learning (EBL) technique to parsing Lexicalized Tree-Adjoining grammars. The novel aspects are (a) immediate generalization of parses in the training set, (b) generalization over recursive structures and (c) representation of generalized parses as Finite State Transducers. A highly impoverished parser called a "stapler" has also been introduced. We present experimental results using EBL for different corpora and architectures to show the effectiveness of our approach.
5138605
String Adjunct Grammars
In this paper, we have introduced a new style of formal grammars called String Adjunct Grammars (AG). The rules in an AG have a considerably different formal character as compared to the 'rewrite rule' in a Phrase Structure Grammar (PSG). Such a study of formal grammars of different styles (i.e., formal character of rules) is of great interest because each style is well suited for characterizing certain aspects of natural language structure and is awkward for characterizing certain other aspects. Several subclasses of AG's motivated by strong linguistic considerations have been studied, comparing them with PSG's. Linguistic relevance of these grammars (and other gram mars suggested by this study) has been discussed at the end.
26732443
Preventing False Inferences
I I n t r o d u c t i o n In cooperative man-machine interaction, it is taken as necessary that a system truthfully and informatively respond to a user's question. It is not, however, sufficient. In particular, if the system has reason to believe that its planned response nfight lead the user to draw an inference that it knows to be false, then it must block it by nmdifying or adding to its response. The problem is that a system neither can nor should explore all eonchtsions a user might possibly draw: its reasoning must be constrained in some systematic and well-motivated way. Such cooperative behavior was investigated in [5], in which a modification of Griee's Maxim of Quality is proposed: Grice's Maxim of QualityDo not say what you believe to be false or for which you lack adequate evidence. Joshi's Revised Maxim of Quality If you, the speaker, plan to say anything which may imply for the hearer something that you believe to be false, then provide further information to block it. This behavior was studied in the context of interpreting certain definite noun phrases. In this paper, we investigate this revised principle as applied to question answering. In particular the goals of the research described here are to: I. characterize tractable cases in which the system as respondent (R) can anticipate the possibility of the user/questioner (Q) drawing false conclusions from its response and can hence alter or expand its response so as to prevent it happening; 2. develop a formal method for computing the projected inferences that Q may draw from a particular response, identifying those 1This work is partially supported by NSF Grants MCS 81-07290, MCS 8.3-05221, and [ST 83-11,100. 2At present visiting the Department of Computer and Information Science, University of Pennsylvania, Philadelphia, PA 19104. factors whose presence or absence catalyzes the inferences; 3. enable the system to generate modifications of its response that can defuse possible false inferences and that [nay provide additional useful information as well. Before we begin, it is important to see how this work differs from our related work on responding when the system notices a discrepancy between its beliefs and those of its user [7, 8, 9, 18]. For example, if a user asks • How many French students failed CSEI21 last t e rm? ' , he shows that he .believes inter alia that the set of French students is non-empty, that there is a course CSEI21, and that it, was given last term. If the system simply answers " N o n e ' , he will assume the system concurs w'ith these b~diefs since the answer is consistent with them. Furthermore, he may conclude that French students do r;'d.her well in a difficult course. But this may be a false conclusion if the system doesn' t hold to all of those beliefs (e.g., it doesn' t know of any French students). Thus while the system's assertion "No French students failed CSEI21 last term" is true, it has misled the user (1) inlo believing it concurs with the user's beliefs and (2) into drawing additional false conclusions from its response. 3 The differences between this related work and the current enterprise are that: 1. It is no_~t assumed in the current enterprise that there is any overt indication that the domain beliefs of the user are in any way at odds with those of the system. 2. In our related work, the user draws a false conclusion from what is said because the presuppositions of the response are not in accord with the system's beliefs {following a nice analysis in [lO]). In the current enterpri.~e, the us~,r draws a false conclusion from what is said because the system's response behavior is not in accord with the user's expectations. It. may or may not also 31t is a feature of Kaplan's CO-OP system [7] that it point~ out the discrepancy by saying "| don't know of any French students °
9264341
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.
38151734
Role of Constrained Computational Systems in Natural Language Processing
Abstract The use of constrained formal/computational systems just adequate for modeling various aspects of language—syntax, semantics, pragmatics and discourse, among others, has proved to be an effective research strategy leading to deep understanding of these aspects, with implications to both machine processing and human processing. This approach enables one to distinguish between the universal and stipulative constraints. This is in contrast to an approach where we start with the most powerful formal/computational system and then model the phenomena by making all constraints stipulative in a sense. The use of constrained systems for modeling leads to some novel ways of describing locality of structures and brings out the relationship between the complexity of description of primitives and local computations over them. These ideas serve to unify theoretical, computational and statistical aspects of natural languages processing in AI. It is expected that this approach will be productive in other domains of AI.
41591052
A Tree Generating System
8713624
Intelligent agents meet semantic web in a smart meeting room
We describe a new smart meeting room system called EasyMeeting that explores the use of FIPA agent technologies, Semantic Web ontologies, logic reasoning, and security and privacy policies. Building on a pervasive computing system that we have developed previously, EasyMeeting can provide relevant services and information to meeting participants based on their situational needs. Our system exploits the context-aware support provided by the Context Broker Architecture (CoBrA). Central to CoBrA is an intelligent broker agent that maintains a shared model of context for all computing entities in the space and enforces the privacy policies defined by the users. We also describe the use of CoBrA ontologies, logic reasoning, and privacy protection mechanisms, and evaluate our initial user experience studies.
448895
Search on the Semantic Web
To help human users and software agents find relevant knowledge on the Semantic Web, the Swoogle search engine discovers, indexes, and analyzes the ontologies and facts that are encoded in Semantic Web documents.
6404739
How the Semantic Web is Being Used: An Analysis of FOAF Documents
Semantic Web researchers have initially focused on the representation, development and use of ontologies but paid less attention to the social and structural relationships involved. The past year has seen a dramatic increase in the amount of published RDF documents using the Friend of a Friend (FOAF) vocabulary, providing a valuable resource for investigating how early Semantic Web adopters use this technology as well as build social networks. We describe an approach to identify, discover, and analyze FOAF documents. Over 1.5 million of FOAF documents are collected to show the variety and scalability of the web of FOAF documents. We analyzed the empirical usage of namespace and properties in the FOAF community, which helps the FOAF project in standardizing vocabularies. We also analyzed the social networks induced by those FOAF documents and revealed interesting patterns which can become powerful resource for outsourcing and justification of scientific knowledge.
6376128
Toward Distributed service discovery in pervasive computing environments
The paper proposes a novel distributed service discovery protocol for pervasive environments. The protocol is based on the concepts of peer-to-peer caching of service advertisements and group-based intelligent forwarding of service requests. It does not require a service to be registered with a registry or lookup server. Services are described using the Web Ontology Language (OWL). We exploit the semantic class/subClass hierarchy of OWL to describe service groups and use this semantic information to selectively forward service requests. OWL-based service description also enables increased flexibility in service matching. We present simulation results that show that our protocol achieves increased efficiency in discovering services (compared to traditional broadcast-based mechanisms) by efficiently utilizing bandwidth via controlled forwarding of service requests.
5320074
Using Lexicalized Tags for Machine Translation
Lexicalized Tree Adjoining Grammar (LTAG) is an attractive formalism for linguistic description mainly because of its extended domain of locality and its factoring recursion out from the domain of local dependencies (Joshi, 1985, Kroch and Joshi, 1985, Abeille, 1988). LTAG's extended domain of locality enables one to localize syntactic dependencies (such as filler-gap), as well as semantic dependencies (such as predicate-arguments). The aim of this paper is to show that these properties combined with the lexicalized property of LTAG are especially attractive for machine translation.The transfer between two languages, such as French and English, can be done by putting directly into correspondence large elementary units without going through some interlingual representation and without major changes to the source and target grammars. The underlying formalism for the transfer is "synchronous Tree Adjoining Grammars" (Shieber and Schabes [1990]). Transfer rules are stated as correspondences between nodes of trees of large domain of locality which are associated with words. We can thus define lexical transfer rules that avoid the defects of a mere word-to-word approach but still benefit from the simplicity and elegance of a lexical approach.We rely on the French and English LTAG grammars (Abeille [1988], Abeille [1990 (b)], Abeille et al. [1990], Abeille and Schabes [1989, 1990]) that have been designed over the past two years jointly at University of Pennsylvania and University of Paris 7-Jussieu.