1,446 research outputs found

    A common ground for virtual humans: using an ontology in a natural language oriented virtual human architecture

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    When dealing with large, distributed systems that use state-of-the-art components, individual components are usually developed in parallel. As development continues, the decoupling invariably leads to a mismatch between how these components internally represent concepts and how they communicate these representations to other components: representations can get out of synch, contain localized errors, or become manageable only by a small group of experts for each module. In this paper, we describe the use of an ontology as part of a complex distributed virtual human architecture in order to enable better communication between modules while improving the overall flexibility needed to change or extend the system. We focus on the natural language understanding capabilities of this architecture and the relationship between language and concepts within the entire system in general and the ontology in particular. 1

    Supporting Management lnteraction and Composition of Self-Managed Cells

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    Management in ubiquitous systems cannot rely on human intervention or centralised decision-making functions because systems are complex and devices are inherently mobile and cannot refer to centralised management applications for reconfiguration and adaptation directives. Management must be devolved, based on local decision-making and feedback control-loops embedded in autonomous components. Previous work has introduced a Self-Managed Cell (SMC) as an infrastructure for building ubiquitous applications. An SMC consists of a set of hardware and software components that implement a policy-driven feedback control-loop. This allows SMCs to adapt continually to changes in their environment or in their usage requirements. Typical applications include body-area networks for healthcare monitoring, and communities of unmanned autonomous vehicles (UAVs) for surveillance and reconnaissance operations. Ubiquitous applications are typically formed from multiple interacting autonomous components, which establish peer-to-peer collaborations, federate and compose into larger structures. Components must interact to distribute management tasks and to enforce communication strategies. This thesis presents an integrated framework which supports the design and the rapid establishment of policy-based SMC interactions by systematically composing simpler abstractions as building elements of a more complex collaboration. Policy-based interactions are realised – subject to an extensible set of security functions – through the exchanges of interfaces, policies and events, and our framework was designed to support the specification, instantiation and reuse of patterns of interaction that prescribe the manner in which these exchanges are achieved. We have defined a library of patterns that provide reusable abstractions for the structure, task-allocation and communication aspects of an interaction, which can be individually combined for building larger policy-based systems in a methodical manner. We have specified a formal model to ensure the rigorous verification of SMC interactions before policies are deployed in physical devices. A prototype has been implemented that demonstrates the practical feasibility of our framework in constrained resources

    The pragmatic proof: hypermedia API composition and execution

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    Machine clients are increasingly making use of the Web to perform tasks. While Web services traditionally mimic remote procedure calling interfaces, a new generation of so-called hypermedia APIs works through hyperlinks and forms, in a way similar to how people browse the Web. This means that existing composition techniques, which determine a procedural plan upfront, are not sufficient to consume hypermedia APIs, which need to be navigated at runtime. Clients instead need a more dynamic plan that allows them to follow hyperlinks and use forms with a preset goal. Therefore, in this paper, we show how compositions of hypermedia APIs can be created by generic Semantic Web reasoners. This is achieved through the generation of a proof based on semantic descriptions of the APIs' functionality. To pragmatically verify the applicability of compositions, we introduce the notion of pre-execution and post-execution proofs. The runtime interaction between a client and a server is guided by proofs but driven by hypermedia, allowing the client to react to the application's actual state indicated by the server's response. We describe how to generate compositions from descriptions, discuss a computer-assisted process to generate descriptions, and verify reasoner performance on various composition tasks using a benchmark suite. The experimental results lead to the conclusion that proof-based consumption of hypermedia APIs is a feasible strategy at Web scale.Peer ReviewedPostprint (author's final draft

    Compositional Reactive Synthesis for Multi-Agent Systems

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    With growing complexity of systems and guarantees they are required to provide, the need for automated and formal design approaches that can guarantee safety and correctness of the designed system is becoming more evident. To this end, an ambitious goal in system design and control is to automatically synthesize the system from a high-level specification given in a formal language such as linear temporal logic. The goal of this dissertation is to investigate and develop the necessary tools and methods for automated synthesis of controllers from high-level specifications for multi-agent systems. We consider systems where a set of controlled agents react to their environment that includes other uncontrolled, dynamic and potentially adversarial agents. We are particularly interested in studying how the existing structure in systems can be exploited to achieve more efficient synthesis algorithms through compositional reasoning. We explore three different frameworks for compositional synthesis of controllers for multi-agent systems. In the first framework, we decompose the global specification into local ones, we then refine the local specifications until they become realizable, and we show that under certain conditions, the strategies synthesized for the local specifications guarantee the satisfaction of the global specification. In the second framework, we show how parametric and reactive controllers can be specified and synthesized, and how they can be automatically composed to enforce a high-level objective. Finally, in the third framework, we focus on a special but practically useful class of multi-agent systems, and show how by taking advantage of the structure in the system and its objective we can achieve significantly better scalability and can solve problems where the centralized synthesis algorithm is infeasible

    A knowledge-level model for concurrent design.

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    The concurrent approach to engineering design, concurrent design, implies that expert knowledge regarding a number of different downstream life-cycle perspectives (such as assembly, manufacture, maintainability etc) should all be considered at the design stage of a product's life-cycle. Extensive and valuable work has been done in developing computer aids to both the design and concurrent design processes. However, a criticism of such tools is that their development has been driven by computational considerations and that the tools are not based on a generally accepted model of the design process. Different models of design have been developed that fall into a number of paradigms, including cognitive and knowledge-level models. However, while there is no generally accepted cognitive model describing the way designers and design teams think, the concept of the knowledge-level has enabled a more pragmatic approach to be taken to the development of models of problem-solving activity.Different researchers have developed knowledge-level models for the design process, particularly as part of the CommonKADS methodology (one of the principal knowledge-based system development methodologies currently in use). These design models have significantly extended design thinking in this area. However, the models do not explicitly support the concurrent design process. I have developed top-down knowledge-level models of the concurrent design process by analysis of published research and discussions with academics. However some researchers have criticised models for design that are not based on analysis of 'real-life' design. Hence I wished to validate my top-down models by analysing how concurrent design actually occurs in a real-life industrial setting.Analysing concurrent design activity is a complex process and there are no definitive methodological guidelines as to the 'right way' to do it. Therefore I have developed and utilised a novel method of knowledge elicitation and analysis to develop 'bottom-up' models for concurrent design. This is based on a number of different approaches and was done in collaboration with a number of different design teams and organisations who are engaged in the concurrent design of mechanically based products.My resulting knowledge-level models are an original contribution to knowledge. They suggest that the concurrent design process consists of a number of discrete sub-tasks of propose, critique and negotiate. These models have been instantiated as generic model templates, using the modelling formalisms specified by CommonYADS. These models have been implemented on a software tool, the CommonKADS workbench, in order to provide support for developers of computer-based systems for concurrent design

    Designing Trustworthy Autonomous Systems

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    The design of autonomous systems is challenging and ensuring their trustworthiness can have different meanings, such as i) ensuring consistency and completeness of the requirements by a correct elicitation and formalization process; ii) ensuring that requirements are correctly mapped to system implementations so that any system behaviors never violate its requirements; iii) maximizing the reuse of available components and subsystems in order to cope with the design complexity; and iv) ensuring correct coordination of the system with its environment.Several techniques have been proposed over the years to cope with specific problems. However, a holistic design framework that, leveraging on existing tools and methodologies, practically helps the analysis and design of autonomous systems is still missing. This thesis explores the problem of building trustworthy autonomous systems from different angles. We have analyzed how current approaches of formal verification can provide assurances: 1) to the requirement corpora itself by formalizing requirements with assume/guarantee contracts to detect incompleteness and conflicts; 2) to the reward function used to then train the system so that the requirements do not get misinterpreted; 3) to the execution of the system by run-time monitoring and enforcing certain invariants; 4) to the coordination of the system with other external entities in a system of system scenario and 5) to system behaviors by automatically synthesize a policy which is correct

    A unified approach to planning support in hierarchical coalitions

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    Early aspects: aspect-oriented requirements engineering and architecture design

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    This paper reports on the third Early Aspects: Aspect-Oriented Requirements Engineering and Architecture Design Workshop, which has been held in Lancaster, UK, on March 21, 2004. The workshop included a presentation session and working sessions in which the particular topics on early aspects were discussed. The primary goal of the workshop was to focus on challenges to defining methodical software development processes for aspects from early on in the software life cycle and explore the potential of proposed methods and techniques to scale up to industrial applications
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