9907384
Integrating Joint Intention Theory, Belief Reasoning, and Communicative Action for Generating Team-Oriented Dialogue
The goal of this research is to develop an architecture that can guide an agent during collaborative teamwork. The architecture should generate communication and dialogue during the performance of collaborative multi-agent tasks as a byproduct of the agent's rationally pursuing its intentions. This paper describes how a joint intention interpreter that is integrated with a reasoner over beliefs and communicative acts can form the core of a dialogue engine. As an interpreter of joint actions, the architecture enables agent programmers to describe a domain declaratively, specifying an agent's individual and joint intentions, plans and actions at a high level. The interpreter attempts to fulfill the agent's individual and joint intentions, subject to its beliefs and mutual beliefs. As a consequence, the system engages in dialogue through the planning and execution of communicative acts necessary to attain the collaborative task at hand. The dialogue engine is general enough to be applicable to both agent-agent and agent-human teams. The system has been implemented in a combination of Java and Prolog, and can be shown to obey the predictions of joint intention.
3185097
Towards a fault-tolerant multi-agent system architecture
Multi-agent systems are prone to failures typical of any distributed system. Agents and resources may become unavailable due to machine crashes, communication breakdowns, process failures, and numerous other hardware and software failures. Most of the work done in fault handling in multi-agent systems deals with detection and recovery from faults such as state-inconsistencies, relying on the traditional techniques for recovering from other distributed systems failure. However, the traditional fault-tolerance techniques are designed for specific situations and they require special infrastructural support. We argue for fault-tolerance techniques that can be readily implemented using a generic agent shell with minimal or no modification to the agent infrastructure. We propose that theories from multi-agent systems literature can be effectively combined with basic fault-tolerance principles to design robust multi-agent systems. In particular, we argue that (1) teamwork may be used to create a robust brokered architecture that can recover a multi-agent system from broker failures without incurring undue overheads, (2) teamwork may also be used to guarantee a specified number of brokers in a large multi-agent system, and (3) agent autonomy can be used to prevent thrashing and guarantee acceptable levels of quality of service by an agent. We also describe the Adaptive Agent Architecture (AAA), a fault-tolerant brokered multi-agent system architecture, and present experimental evidence using the AAA to validate our approach.
15419677
STAPLE: An agent programming language based on the joint intention theory
Joint intention theory has been used for rule based creation of teams and to provide a formal semantics for communicative acts but there were no agent programming languages linked to this theory. We proposed a declarative agent programming language called STAPLE whose logical semantics is given by the joint intention theory. This paper illustrates the STAPLE support for communication and teamwork in a unified framework.
17321819
Toward A Formalism for Conversation Protocols Using Joint Intention Theory
Conversation protocols are meant to achieve certain tasks or to bring about certain state of affairs in the world. Therefore, one may identify the landmarks or the state of affairs that must be brought about during the execution of a protocol in order to achieve its goal. Accordingly, the most important aspect of protocols is these landmarks rather than the communicative actions needed to achieve the landmarks. We show that families of conversation protocols can be expressed formally as partially ordered landmarks where each landmark is characterized by propositions that are true in the state represented by that landmark. Dialogue in natural languages is regarded as joint activity. Conversation protocols in multi-agent systems are treated as dialogue templates and are composed using speech acts from natural language dialogues. As such, we treat conversation protocols as joint action expressions and gainfully apply existing formal theories of dialogue, specifically the Joint Intention Theory, to protocols and their compositions. Conversation protocols may require agents to communicate with groups as well as individuals. However, most contemporary agent communication languages, notably FIPA and KQML, have either no provision or no well-defined semantics for group communication. Furthermore, the research on protocols so far does not correctlymore » incorporate groups into the protocols. We give a formal semantics to group communicative acts and use it to handle group communication in a formal treatment of protocols.« less
14123026
Distributive and Collective Readings in Group Protocols
Collaborative applications require protocols that specify how distributed entities interact with one another in order to achieve a specified behavior. Many different kinds of relationships can be established between these entities as a result of such interactions. Distributive and Collective readings are two important ways to characterize group interaction. Starting from an attempt-based semantics of group communicative acts, we distinguish between these two concepts and evaluate group protocols with respect to formation of different types of teams during the interaction.
13307472
Direct execution of team specifications in STAPLE
Formal theories of teamwork are typically treated as software design specifications of team behavior. We take a different approach to programming teamwork by directly executing logical specifications of joint commitment and joint intention. This approach leads to a domain-independent framework for programming teamwork where one can modify (or add new) behavior for a team of agents just by modifying (or adding) logical sentences. One may also be able to predict the behavior of an agent team offline using its team intention specification and verify it by running the actual system.
8714791
Hybrid transactional memory
High performance parallel programs are currently difficult to write and debug. One major source of difficulty is protecting concurrent accesses to shared data with an appropriate synchronization mechanism. Locks are the most common mechanism but they have a number of disadvantages, including possibly unnecessary serialization, and possible deadlock. Transactional memory is an alternative mechanism that makes parallel programming easier. With transactional memory, a transaction provides atomic and serializable operations on an arbitrary set of memory locations. When a transaction commits, all operations within the transaction become visible to other threads. When it aborts, all operations in the transaction are rolled back.Transactional memory can be implemented in either hardware or software. A straightforward hardware approach can have high performance, but imposes strict limits on the amount of data updated in each transaction. A software approach removes these limits, but incurs high overhead. We propose a novel hybrid hardware-software transactional memory scheme that approaches the performance of a hardware scheme when resources are not exhausted and gracefully falls back to a software scheme otherwise.
2832297
Design of randomized multichannel packet storage for high performance routers
High performance routers require substantial amounts of memory to store packets awaiting transmission, requiring the use of dedicated memory devices with the density and capacity to provide the required storage economically. The memory bandwidth required for packet storage subsystems often exceeds the bandwidth of individual memory devices, making it necessary to implement packet storage using multiple memory channels. This raises the question of how to design multichannel storage systems that make effective use of the available memory and memory bandwidth, while forwarding packets at link rate in the presence of arbitrary packet retrieval patterns. A recent series of papers has demonstrated an architecture that uses on-chip SRAM to buffer packets going to/from a multichannel storage system, while maintaining high performance in the presence worst-case traffic patterns. Unfortunately, the amount of on-chip storage required grows as the product of the number of channels and the number of separate queues served by the packet storage system. This makes it too expensive to use in systems with large numbers of queues. We show how to design a practical randomized packet storage system that can sustain high performance using an amount of on-chip storage that is independent of the number of queues.
7470034
Recognition of human actions using moment based features and artificial neural networks
This paper presents performance of view-based approach in automated recognition of predefined hand and gross body actions using artificial neural network. This approach represents motion by a static grey scale image template computed by collapsing the temporal components into the cumulative image-difference of frames. The seven invariant Hu moments are used as the feature vectors. The performance of the system is tested in real time using feed forward multilayer perceptron (MLP) based on back propagation.
6728312
Evaluating synchronization on shared address space multiprocessors: methodology and performance
Synchronization is an area that exhibits rich hardware-software interactions in multiprocessors. It was studied extensively using microbenchmarks a decade ago. However, its performance implications are not well understood on modern systems or on real applications. We study the impact of synchronization primitives and algorithms on a modern, 64processor, hardware-coherent shared address space multiprocessor: the SGI Origin 2000. In addition to the actual results on a modern system, we examine the key methodological issues in studying synchronization, for both microbenchmarks and applications. We find that although the efficient hardware support (Fetch&Op) for synchronization provided on our machine usually helps lock and barrier microbenchmarks, it does not help in improving application performance when compared to good software algorithms that use the processor-provided LL-SC instructions. This is true even in applications that spend a significant amount of time in synchronization operations. More elaborate hardware support is unlikely to have a significant benefit either. From the applications’ perspective, it is usually the waiting time due to load imbalance or serialization that dominates synchronization time, not the overhead of the synchronization operations themselves, even in apparently balanced cases where the overhead may be expected to be substantial.
16861729
Normalization of non-standard words
In addition to ordinary words and names, real text contains non-standard “words" (NSWs), including numbers, abbreviations, dates, currency amounts and acronyms. Typically, one cannot find NSWs in a dictionary, nor can one find their pronunciation by an application of ordinary “letter-to-sound" rules. Non-standard words also have a greater propensity than ordinary words to be ambiguous with respect to their interpretation or pronunciation. In many applications, it is desirable to “normalize" text by replacing the NSWs with the contextually appropriate ordinary word or sequence of words. Typical technology for text normalization involves sets of ad hoc rules tuned to handle one or two genres of text (often newspaper-style text) with the expected result that the techniques do not usually generalize well to new domains. The purpose of the work reported here is to take some initial steps towards addressing deficiencies in previous approaches to text normalization. We developed a taxonomy of NSWs on the basis of four rather distinct text types?news text, a recipes newsgroup, a hardware-product-specific newsgroup, and real-estate classified ads. We then investigated the application of several general techniques including n-gram language models, decision trees and weighted finite-state transducers to the range of NSW types, and demonstrated that a systematic treatment can lead to better results than have been obtained by the ad hoc treatments that have typically been used in the past. For abbreviation expansion in particular, we investigated both supervised and unsupervised approaches. We report results in terms of word-error rate, which is standard in speech recognition evaluations, but which has only occasionally been used as an overall measure in evaluating text normalization systems.