16208693
Some results in tree automata
In this paper, we will essentially present three results in tree automata. Two of these are concerned with certain open problems posed by Rounds [1] and Martin and Vere [3], and the third one is related to the result of Peters and Ritchie [4].
 First we will briefly state the results and then describe them in some detail in Sections 2, 3, and 4.
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.
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.
14038978
Intelligent Agents Meet the Semantic Web in Smart Spaces
A new smart meeting room system called EasyMeeting explores the use of multi-agent systems, Semantic Web ontologies, reasoning, and declarative policies for security and privacy. Building on an earlier pervasive computing system, EasyMeeting provides relevant services and information to meeting participants based on their situational needs. The system also exploits the context-aware support provided by the Context Broker Architecture (Cobra). Cobra's intelligent broker agent maintains a shared context model for all computing entities in the space and enforces user-defined privacy policies.
2898024
Using OWL in a Pervasive Computing Broker
Computing is moving toward a pervasive context-aware environment in which agents with limited resources will require external support to help them become context-aware. In this paper, we describe an agent based architecture called Context Broker Architecture (CoBrA) to help these agents to acquire, reason about and share context knowledge. A key component in our architecture is an explicit context ontology defined using the Web Ontology Language (OWL). This ontology models the basic concepts of people, agents, places, and presentation events. We also describe a use case scenario and prototype design of CoBrA in an intelligent meeting room environment.
7627284
Information Retrieval and the Semantic Web
Information retrieval technology has been central to the success of the Web. For semantic web documents or annotations to have an impact, they will have to be compatible with Web based indexing and retrieval technology. We discuss some of the underlying problems and issues central to extending information retrieval systems to handle annotations in semantic web languages. We also describe three prototype systems that we have implemented to explore these ideas.
2902172
On correspondence, line tokens and missing tokens
In this article, the authors expand on some of their previous work on correspondence and propose a system that can correspond in the presence of both point and line tokens, or a mix of them. It can also work if some tokens present in one frame are not present in the other. The proposed algorithm is an amalgamation of reductionist and holist paradigms. We establish that properties which remain invariant for whole image sequences and sequences consisting of corresponding parts from each image frame can be used to establish correspondence. Extensive computer simulation results on synthesised data as well as real image sequences are presented to validate our claims.
40577335
Service Composition for Mobile Environments
Service Composition, that is, the development of customized services by discovering, integrating and executing existing services has received a lot of attention in the last couple of years with respect to wired-infrastructure or Internet web services. With the advancement in the wireless technology and rapid deployment of mobile devices, we envision that in the near future wirelessly connected mobile devices in a given vicinity will also provide services that can be leveraged in the composition process. This is particularly true of what have been described as “pervasive computing” environments. However, wired-infrastructure based service composition architectures are not designed to consider the various factors like mobility, device heterogeneity, resource variability and reliability in a mobile environment. In this paper, we describe the issues related to service composition in mobile environments and evaluate criteria for judging protocols that enable such composition. We present a distributed architecture and associated protocols for service composition in mobile environments that take into consideration mobility, dynamic changing service topology and device resources. The composition protocols are based on distributed brokerage mechanisms and utilize a distributed service discovery process over ad-hoc network connectivity. We present simulation results of our protocols, and compare them with a centralized service composition protocol traditionally used for wired-infrastructure environments. The results show that our approach clearly outperforms the existing centralized approaches, and that our protocols are able to adapt and better utilize the changing service topology and resources in a mobile environment.