3D C-string: a new spatio-temporal knowledge representation for video database systems

In video database systems, one of the most important methods for discriminating the videos is by using the objects and the perception of spatial and temporal relations that exist between objects in the desired videos. In this paper, we propose a new spatio-temporal knowledge representation called 3D C-string. The knowledge structure of 3D C-string, extended from the 2D C⁺-string, uses the projections of objects to represent spatial and temporal relations between the objects in a video. Moreover, it can keep track of the motions and size changes of the objects in a video. The string generation and video reconstruction algorithms for the 3D C-string representation of video objects are also developed. By introducing the concept of the template objects and nearest former objects, the string generated by the string generation algorithm is unique for a given video and the video reconstructed from a given 3D C-string is unique too. This approach can provide us an easy and efficient way to retrieve, visualize and manipulate video objects in video database systems. Finally, some experiments are performed to show the performance of the proposed algorithms.     

On computing the worst-case peak gain of linear systems

Based on the bounds due to Doyle and Boyd, we present simple upper and lower bounds for the l¹-norm of the ‘tail’ of the impulse response of finite-dimensional discrete-time linear time-invariant systems. Using these bounds, we may in turn compute the l^∞-gain of these systems to any desired accuracy. By combining these bounds with results due to Khammash and Pearson, we derive upper and lower bounds for the worst-case l^∞-gain of discrete-time systems with diagonal perturbations.     

A note on the structure of two subsets of the parameter space in adaptive control problems

We study the geometric structure of two subsets of the parameter space that are of interest in the context of adaptive LQ-control. The first set can be considered as the set of possible limit points of an adaptive control algorithm, whereas the second can be seen as the set of desirable limit points. Our main result is that these sets are C^ω-manifolds.     

Index set: A practical indexing scheme for object database systems

Efficient indexing in a class hierarchy is essential for the achievement of high performance in query evaluation for object database management systems. In this paper, we present a practical indexing scheme, index set, which provides good index configuration for any real database environment. The proposed scheme considers the distribution of key values, as well as query patterns such as query weight on each class. The index set can easily be applied to any database system, since it uses the well-known B⁺-tree structure. We develop a cost model and, through experiments, demonstrate the performance of the proposed scheme over various class hierarchies.     

Stabilization and H control of symmetric systems: an explicit solution

In this paper we address the H^∞ control analysis, the output feedback stabilization, and the output feedback H^∞ control synthesis problems for state-space symmetric systems. Using a particular solution of the Bounded Real Lemma for an open-loop symmetric system we obtain an explicit expression to compute the H^∞ norm of the system. For the output feedback stabilization problem we obtain an explicit parametrization of all asymptotically stabilizing control gains of state-space symmetric systems. For the H^∞ control synthesis problem we derive an explicit expression for the optimally achievable closed-loop H^∞ norm and the optimal control gains. Extension to robust and positive real control of such systems are also examined. These results are obtained from the linear matrix inequality formulations of the stabilization and the H^∞ control synthesis problems using simple matrix algebraic tools.     

An H-minimax approach to the design of robust control systems

A realistic feedback design problem is posed based on the minimization of a weighted combination of the sensitivity and complementary sensitivity matrices. A solution is obtained which makes use of the recently proposed methods for minimizing the sensitivity function alone.     

Modelling the impact of study behaviours on academic performance to inform the design of a persuasive system

Information technology is deeply ingrained in most aspects of everyday life and can be designed to influence users to behave in a certain way. Influencing students to improve their study behaviour would be a useful application of this technology. As a preamble to the design of a persuasive system for learning, we collected data to identify the study behaviours of students and recent alumni. We then developed two models to measure which behaviours have the most significant impact on learning performance. Current students reported more foundational behaviours whereas alumni demonstrated more higher-order thinking traits.     

Heuristic search for scheduling flexible manufacturing systems using lower bound reachability matrix

For scheduling flexible manufacturing systems efficiently, we propose new heuristic functions for A^* algorithm that is based on the T-timed Petri net. In minimizing makespan, the proposed heuristic functions are usually more efficient than the previous functions in the required number of states and computation time. We prove that these heuristic functions are all admissible and one of them is more informed than that using resource cost reachability matrix. We also propose improved versions of these heuristic functions that find a first near-optimal solution faster. In addition, we modify the heuristic function of Yu, Reyes, Cang, and Lloyd (2003b) and propose an admissible version in all states. The experimental results using a random problem generator show that the proposed heuristic functions perform better as we expected.     

Supporting management and maintenance of manufacturing knowledge in design automation systems

Many companies base their business strategy on customized products. To enable a high level of product adaptation in an engineer-to-order approach companies invest time and resources to develop design automation systems. Initially, when implementing a design automation system, the focus is on successfully developing a system that generates design variants based on different customer specifications (i.e. the execution of system embedded knowledge and system output). However, in the long run, two important aspects are the management and maintenance of the knowledge that governs the designs. Further, the increasing emphasis on deploying a holistic view of a product’s properties and functions implies an increasing number of life-cycle requirements. The knowledge to adapt the product to fulfil these requirements should also be used and consequently incorporated into the knowledge-base, allowing for correct decisions to be made. In a system for automated variant design, the implications on the product of these life-cycle requirements have to be expressed as algorithms, production rules and/or computational statements to be intertwined with the design calculations. The number of requirements can be significantly large, and the knowledge scattered over different application systems used for the realisation of the design automation system. This makes it difficult to manage and maintain the system as the product life-cycle environment changes and evolves.In this article, the focus is on the requirements related to manufacturing. For that, an approach for the modelling of manufacturing requirements, supporting both knowledge execution and information management, in systems for automated variant design is introduced. The approach has been applied and refined when developing a design automation system in cooperation with a company to demonstrate and verify the approach’s usability.     

Convergence analysis for reduced-order adaptive controller design of uncertain SISO linear systems with noisy output measurements

We consider in this article a class of uncertain SISO linear systems that are subject to system and measurement noises. Reduced-order adaptive controller designs have been proposed before for such systems by the authors and stability analysis of the closed-loop systems has been established. Here we analyse, further, the robustness properties for these reduced-order adaptive control systems by providing detailed convergence analysis results for the key closed-loop signals and parameter estimates. We rigorously prove that, whenever the exogenous disturbance input is of finite energy and bounded, and the reference trajectory and its derivatives up to rth order are bounded, r being the relative degree of the transfer function of the true system, a set of signals, including the tracking error, the estimation error between the system output and its estimate, the projection signal, are of finite energy and converge to zero; and the system states and their estimates exhibit asymptotic behaviours with certain formats. With an additional persistency of excitation condition, it is also proved that the estimate and the worst-case estimate of the state vector asymptotically track the actual state vector; and the estimate and the worst-case estimate of the unknown parameter vector converge to the true value. A numerical example is given to illustrate the theoretical findings.     

Controllability of linear systems in Banach spaces

The problem of controllability of linear systems in Banach spaces is considered. First, some properties of dual semigroups with respect to Lebesgue measure is presented. Then, based on the properties, the criteria for controllability in reflexive Banach spaces are extended to general Banach spaces and some new criteria for controllability are established. An example is presented to show that the scope of controllable systems can be enlarged if the non-traditional space of control functions is used.     

Specification, decomposition and agent synthesis for situation-aware service-based systems

Service-based systems are distributed computing systems with the major advantage of enabling rapid composition of distributed applications, such as collaborative research and development, e-business, health care, military applications and homeland security, regardless of the programming languages and platforms used in developing and running various components of the applications. In dynamic service-oriented computing environment, situation awareness (SAW) is needed for system monitoring, adaptive service coordination and flexible security policy enforcement. To greatly reduce the development effort of SAW capability in service-based systems and effectively support runtime system adaptation, it is necessary to automate the development of reusable and autonomous software components, called SAW agents, for situation-aware service-based systems. In this paper, a logic-based approach to declaratively specifying SAW requirements, decomposing SAW specifications for efficient distributed situation analysis, and automated synthesis of SAW agents is presented. This approach is based on AS³ calculus and logic, and our declarative model for SAW. Evaluation results of our approach are also presented.     

On the weighted sensitivity minimization problem for delay systems

We consider the H^∞-optimal sensitivity problem for delay systems. In particular, we consider computation of μ:= inf {|W-φq|_∞ : q ε H^∞(j )} where W(s) is any function in RH^∞(j ), and φ in H^∞(j ) is any inner function. We derive a new explicit solution in the pure delay case where φ = e^−sh, h > 0.     

Consistency in multi-viewpoint design of enterprise information systems

Different stakeholders in the design of an enterprise information system have their own view on that design. To help produce a coherent design this paper presents a framework that aids in specifying relations and consistency rules between such views. The contribution of our framework is that it provides a collection of basic concepts. These basic concepts aid in relating viewpoints by providing: (i) a common terminology that helps stakeholders to understand each others concepts; and (ii) re-usable consistency rules. We show that our framework can be applied, by performing a case study in which we specify the relations and consistency rules between three RM-ODP viewpoints.     

An interpolation problem associated with H-optimal design in systems with distributed input lags

A variety of H^∞ optimal design problems reduce to interpolation of compressed multiplication operators, f(s) → π_k(w(s)f(s)), where w(s) is a given rational function and the subspace K is of the form K=H² φ(s)H². Here we consider φ(s) = (1-e^α-5)/(s - α), which stands for a distributed delay in a system's input. The interpolation scheme we develop, adapts to a broader class of distributed lags, namely, those determined by transfer functions of the form B(e^−s)/b(s), where B(z) and b(s) are polynomials and b(s) = 0 implies B(e^−s) = 0.     

A formal approach for the development of reactive systems

Context

This paper deals with the development and verification of liveness properties on reactive systems using the Event-B method. By considering the limitation of the Event-B method to invariance properties, we propose to apply the language TLA⁺ to verify liveness properties on Event-B models.

Objective

This paper deals with the use of two verification approaches: theorem proving and model-checking, in the construction and verification of safe reactive systems. The theorem prover concerned is part of the Click_n_Prove tool associated to the Event-B method and the model checker is TLC for TLA⁺ models.

Method

To verify liveness properties on Event-B systems, we extend first the expressivity and the semantics of a B model (called temporal B model) to deal with the specification of fairness and eventuality properties. Second, we propose semantics of the extension over traces, in the same spirit as TLA⁺ does. Third, we give verification rules in the axiomatic way of the Event-B method. Finally, we give transformation rules from a temporal B model into a TLA⁺ module. We present in particular, our prototype system called B2TLA⁺, that we have developed to support this transformation; then we can verify liveness properties thanks to the model checker TLC on finite state systems. For the verification of infinite-state systems, we propose the use of the predicate diagrams and its associated tool DIXIT. As the B refinement preserves invariance properties through refinement steps, we propose some rules to get the preservation of liveness properties by the B refinement.

Results

The proposed approach is applied for the development of some reactive systems examples and our prototype system B2TLA⁺ is successfully used to transform a temporal B model into a TLA⁺ module.

Conclusion

The paper successfully defines an approach for the specification and verification of safety and liveness properties for the development of reactive systems using the Event-B method, the language TLA⁺ and the predicate diagrams with their associated tools. The approach is illustrated on a case study of a parcel sorting system.     

Assessing the contribution of knowledge to business performance: the KP methodology

Knowledge is inherently difficult to measure. However, without valid and reliable measurement, it is very difficult to develop a comprehensive theory of knowledge and provide a practical guide for knowledge management. In this paper, we do not measure knowledge directly, but assess how much knowledge contributes to business performance. The KP³ methodology developed in this paper assesses the contribution of knowledge to business performance by employing product and process as intermediaries between the two. The understanding of the contribution is essential because it makes it possible to assess the productivities of knowledge entities, evaluate and compensate knowledge workers, and to allocate and develop human capital.     

An H-minimax approach to the design of robust control systems, part II: All solutions, all-pass form solutions and the ‘best’ solution

We characterize all solutions to a robustness optimization problem as the solutions of a two-parameter interpolation problem. From this characterization it is easy to show that an all-pass form solution always exists as long as a solution exists. We also study the possibility of using non-all-pass form solutions and by introducing other optimization objectives (motivated by improvements in disturbance rejection and robust stability) we search for the 'best' solution.