A temporal agent based approach for testing open distributed systems

The development of distributed testing frameworks is more complex, where the implementation process must consider the mechanisms and functions required to support interaction as long as the communication and the coordination between distributed testing components. The typical reactions of such systems are the generation of errors‘set: time outs, locks, observability, controllability and synchronization problems. In other side, the distributed testing process must not only check if the output events have been observed, but also the dates when these events have been occurred. In this paper, we show how to cope with these problems by using a distributed testing method including timing constraints. Afterwards, a multi-agent architecture is proposed in the design process to describe the behavior of testing a distributed chat group application on high level of abstraction.     

Using status messages in the distributed test architecture

If the system under test has multiple interfaces/ports and these are physically distributed then in testing we place a tester at each port. If these testers cannot directly communicate with one another and there is no global clock then we are testing in the distributed test architecture. If the distributed test architecture is used then there may be input sequences that cannot be applied in testing without introducing controllability problems. Additionally, observability problems can allow fault masking. In this paper we consider the situation in which the testers can apply a status message: an input that causes the system under test to identify its current state. We show how such a status message can be used in order to overcome controllability and observability problems.     

Distributed testing without encountering controllability and observability problems

The objective of testing is to determine whether a system under test conforms to its specification. In distributed test architectures that utilize remote testers, this objective can be complicated by the fact that testers may encounter problems relating to controllability and observability during the application of a test sequence. Existing solutions to these problems involve first constructing a test sequence from the specification of an implementation under test, and then inserting coordination messages or appending selected test subsequences that prevent the occurrences of controllability and observability problems during the application of the resulting test sequence. This paper proposes a method that utilizes a set of transformation rules to construct an auxiliary directed graph from a given specification, and constructs a rural Chinese postman tour in this graph to yield a minimum-length test sequence where there is no potential controllability or observability problems, and where the use of coordination messages is minimized.     

Constructing checking sequences for distributed testing

The objective of testing is to determine whether an implementation under test conforms to its specification. In distributed test architectures involving multiple remote testers, this objective can be complicated by the fact that testers may encounter coordination problems relating to controllability (synchronization) and observability during the application of tests. Based on a finite state machine (FSM) specification of the externally observable behaviour of a distributed system and a distinguishing sequence, this paper proposes a method for constructing a checking sequence where there is no potential controllability or observability problems, and where the use of external coordination message exchanges among testers is minimized. The proposed method does not assume a reliable reset feature in the implementations of the given FSM to be tested by the resulting checking sequence. phone: 613-562-5800(Extn)6684 Received May 2004 Revised March 2005 Accepted April 2005 by J. Derrick, M. Harman and R. M. Herons     

UIO sequence based checking sequences for distributed test architectures

This study addresses the construction of a preset checking sequence that will not pose controllability (synchronization) and observability (undetectable output shift) problems when applied in distributed test architectures that utilize remote testers. The controllability problem manifests itself when a tester is required to send the current input and because it did not send the previous input nor did it receive the previous output it cannot determine when to send the input. The observability problem manifests itself when a tester is expecting an output in response to either the previous input or the current input and because it is not the one to send the current input, it cannot determine when to start and stop waiting for the output. Based on UIO sequences, a checking sequence construction method is proposed to yield a sequence that is free from controllability and observability problems.     

Coordination Algorithm for Distributed Testing

With the emergence of new models, architectures and middleware such as ODP, TINA and CORBA, for developing open distributed systems, testing technology requires adaptation for use within conformance assessment in such systems. All these frameworks are object-based and aim at creating open distributed environments supporting interworking, interoperability, and portability, in spite of heterogeneity and autonomy of the related systems. In this context, an open distributed system may be viewed as a system providing standardized distributed interfaces for interacting with other systems. Conformance of such a system can be assessed by attaching a related tester at each provided interface. However, many problems of controllability and observability influencing fault detection during the testing process, arise if there is no coordination between the testers. In this paper, we show how to cope with these problems by using test coordination procedures in a distributed testing architecture.     

Checking sequences for distributed test architectures

Controllability and observability problems may manifest themselves during the application of a checking sequence in a test architecture where there are multiple remote testers. These problems often require the use of external coordination message exchanges among testers during testing. However, the use of coordination messages requires the existence of an external network that can increase the cost of testing and can be difficult to implement. In addition, the use of coordination messages introduces delays and this can cause problems where there are timing constraints. Thus, sometimes it is desired to construct a checking sequence from the specification of the system under test that will be free from controllability and observability problems without requiring the use of external coordination message exchanges. This paper gives conditions under which it is possible to produce such a checking sequence, using multiple distinguishing sequences, and an algorithm that achieves this.     

Controllability and observability of linear time-invariant compartmental models

The problems of complete controllability and complete observability of linear time-invariant compartmental models with general input-output structures are considered. The analysis of these problems is based largely on graph-theoretic methods and the properties of polynomial matrices. Specifically, statements on complete controllability and complete observability are proven by using graphical constructions which do not change the basic properties of controllability and observability. The major results of this paper are: 1) A unique decomposition of the digraph of a compartmental model into sources, sinks, and transits. 2) A theorem which states that a compartmental model with closed sinks is completely observable if and only if the matrix [C^{T}, A^{T}] is full rank, and a corollary which provides a sufficient condition for complete observability of all other linear time-invariant compartmental models. 3) A theorem which states that a single sink compartmental model is completely controllable if and only if a compartment from each source is controlled. 4) A controllability algorithm which provides sets of excitations which are sufficient for complete controllability of any linear time-invariant compartmental model.     

Distributed fuzzy discrete event system for robotic sensory information processing

Abstract: This paper presents a novel intelligent sensory information processing technique using a fuzzy discrete event system (FDES) for robotic control. The proposed method combines the predictive control approach of a discrete event system with the approximate reasoning aspect of fuzzy logic. It develops a supervisory control strategy for behavior-based robotic control using distributed FDES. The application of distributed FDES eliminates the formation of complex fuzzy predicates and a large fuzzy rule-base. The FDES-based approach also provides means for analyzing behavior-based decision-making using the observability and controllability of an FDES. The observability of an FDES describes uncertainties in sensory data, and the controllability of an FDES exploits uncertain state transitions in a dynamic environment. Comprehensive experiments on behavior-based mobile robot navigation are presented to authenticate the performance of the proposed methodology.     

基于np-FSM的分布式协议的虚拟多端口测试方法

在协议工程领域,协议测试是非常重要的工作;对于分布式协议的测试多采用多端口有限状态机模型进行描述;由于分布式协议测试存在控制观察问题,需要对测试序列进行同步和协调;通过对现有分布式测试模型的改进,引入虚拟多端口测试的方法,极大地简化了多个测试器之间的同步和协调问题,并且不会显著增加系统的构建成本,提高了测试效率.     

Geometrical tools to map systems of affine recurrence equations on regular arrays

We propose a method based on geometrical tools to map problems onto regular and synchronous processor arrays. The problems we consider are defined by systems of affine recurrence equations (SARE). From such a problem specification we extract the data dependencies in terms of two classes of vectors: the utilization vectors and the dependence vectors. We use these vectors to express constraints on the timing or the allocation functions. We differentiate two classes of constraints. The causal ones are intrinsic timing constraints induced by the system of equations defining the problem. A given choice of target architecture may impose new constraints on the timing or the allocation. We call them the architecture-related constraints. We use these constraints to determine first an affine timing function and next an allocation by projection. We finally illustrate the method with three examples: the matrix multiplication, the recursive convolution and the LL^t Cholesky factorization.     

Graph-based determination of structural controllability and observability for pressure and temperature dynamics during steam-assisted gravity drainage operation

Steam assisted gravity drainage (SAGD), which is used for the in-situ extraction and recovery of oil sands bitumen, is represented by a distributed parameter system (DPS). The problem of sensor placement and the control of steam chamber growth and oil production, respectively, require analysis of the observability and controllability of the system. In this type of system, parametric sensitivity is traditionally used in lieu of observability, and controllability has not been explored rigorously. In this work, we analyze the pressure and temperature fields of a SAGD model based on detailed reservoir simulations and present a data-driven technique to assess the structural controllability and observability of the system, with a view to determine optimal locations of actuators and sensors. An agglomerative hierarchical clustering technique is used to obtain a spanning tree of the clusters which is partitioned based on an objective function to arrive at a set of spatially contiguous clusters that display similar pressure/temperature dynamics. A Granger causality measure is used to create the linkage amongst the clusters to build a digraph model of the data. The driver nodes of the graph identify locations for actuation which provide full control over the graph, and the root strongly connected components indicate sensor locations which ensure structural observability over the entire graph. We demonstrate the method using data generated from SAGD simulations using the CMG-STARS simulator, identify the sensor and actuator locations required for complete structural observability and controllability of the system, and also provide a method of assessment of partial actuation and in-sensor ranges.     

Controllability and observability of 2D thermal flow in bulk storage facilities using sensitivity fields

To control and observe spatially distributed thermal flow systems, the controllable field and observable field around the actuator and sensor are of interest, respectively. For spatially distributed systems, the classical systems theoretical concepts of controllability and observability are, in general, difficult to apply. In this study, sensitivity fields were used to analyse the behaviour from input to state and from initial state to output. For the analysis of controllability and observability, a large-scale, bulk storage facility with coupled thermal flow of air and agro-products was used. Analysis of this system using the classical systems theory results in controllability and observability results that are dependent on the step size of the spatially discretised system. Due to matrix multiplications, inaccurate results are calculated if the step size is too small. Our findings indicate that input-state and initial-state output sensitivity fields provide sufficient information about the controllability and observability of large coupled spatially distributed systems, using finite-dimensional state space representation with small discretisation steps.     

Architecture-based testing of service-oriented applications in distributed systems

ContextTesting distributed service-oriented applications (SOAs) is more challenging than testing monolithic applications since these applications have complex interactions between participant services. Test engineers can observe test results only through a front service that handles request messages sent by test engineers. Message exchanges between participant services are hidden behind the front service and cannot be easily observed or controlled through the front service. For this reason, testing SOAs suffer from limited observability and controllability problem.ObjectiveThis paper proposes a new test method that is architecture-based and exploits interaction architecture of a SOA. The proposed test method alleviates the limited observability and controllability problem by employing test architecture, thereby facilitating test execution and analysis through monitoring and controlling message exchanges.MethodOur proposed method derives an interaction architecture from the specification of a SOA. Test architectures can be designed from the derived interaction architecture by extending it with additional test elements. At the same time, architecture-neutral test scenarios are automatically generated from the test model that is constructed from the specification. Our method combines test architecture information with the test scenarios to obtain architecture-enabled test scenarios under the selected test architectures. Finally, architecture-enabled test execution and analysis are conducted in the real network environment.ResultsThe efficacy of the proposed method is demonstrated with an industrial case study, which shows that it is practical and effective for testing SOAs. Even though our method increases an additional test generation effort owing to test architecture, it is counterbalanced by higher fault detection rate and faster fault locating time.ConclusionThe main benefit of our approach is that using test architecture it enhances testability of SOA by increasing observability and controllability through monitoring and controlling message exchanges. Our architecture-based test method enables test engineers to detect faults efficiently and also reduce fault locating time significantly.     

On the controllability and observability of discrete-time linear time-delay systems

This article studies the controllability and observability of discrete-time linear time-delay systems, so that the two properties can play a more fundamental role in system analysis before controller and observer design is engaged. Complete definitions of controllability and observability, which imply the stabilisability and detectability, respectively, and determine the feasibility of eigenvalue assignment, are proposed for systems with delays in both state variables and input/output signals. Necessary and sufficient criteria are developed to check the controllability and observability efficiently. The proofs are based on the equivalent expanded system, but the criteria only involve the delays and matrices of the same dimension as the original system. Finally, the duality between the suggested controllability and observability is presented.     

Controllability and observability of state‐dependent switched Boolean control networks with input constraints

This paper investigates the controllability and observability of state‐dependent switched Boolean control networks (SDSBCNs) with input constraints. First, the algebraic form of SDSBCNs is derived via the semi‐tensor product of matrices. Then constrained model‐input‐state (CMIS) matrices are introduced for SDSBCNs with input constraints. On the basis of CMIS matrices, two necessary and sufficient conditions are provided for the controllability and observability. Finally, two examples are given to show the effectiveness of the main results.     

基于通信多端口有限状态机的协议互操作性测试生成研究

协议测试是一种保证网络通信协议实现质量的重要技术，互操作性测试是一类常用的协议测试技术．文章提出了一种基于通信多端口有限状态机模型的协议互操作忡测试生成方法．首先采用已有的基于可达性分析的方法生成集中式测试序列；然后采用单一错误模型对其进行系统的错误覆盖分析，为达到更高的错误覆盖度，进一步提出一种增强的测试生成算法；最后讨论了互操作性测试巾的控制观察问题，选择适当的分布式测试架构，并进而生成分布式同步测试序列．实验结果表明：与原有方法相比，该方法可以有效地提高测试集的错误覆盖，并具备一定的可行性和有效性．     

Observability and controllability analysis for sandwich systems with dead-zone

In this paper, an approach to analyze the observability and controllability of sandwich systems with dead-zone is proposed. In this method, a non-smooth state-space function is proposed to describe the sandwich systems with dead-zone which are also non-smooth nonlinear systems. Then, a linearization method based on non-smooth optimization is proposed to derive a linearized state-space function to approximate the non-smooth sandwich systems within a bounded region around the equilibrium points that we are interested in. Afterwards, both observability and controllability matrices are constructed and the methods to analyze the observability as well as controllability of sandwich system with dead-zone are derived. Finally, a numerical example is presented.     

Structure simplification of dynamic process models

Lumped process models derived from first engineering principles are usually too detailed for control purposes where only the major dynamic characteristics of the system should be captured. Two common steps of simplifying dynamic process models, the steady-state variable removal and the variable lumping simplification steps are investigated in this paper, in order to show if they preserve the key properties: the structural controllability, observability and stability of the models. In order to enable the formal analysis, these simplification steps are represented as context sensitive graph transformations acting on the structure graphs of the dynamic process models. It is shown that the simplification transformations above preserve the structural controllability and observability of process models. But only the steady-state variable removal transformation has been found not to destroy their structural stability. The variable lumping structure simplification transformation is further specialized to the case of cascade process models. It is shown that the inverse of this transformation does exist in this case, and both transformations preserve structural controllability and observability.     

Two formal methods for the synthesis of discrete event systems

The design of discrete event systems (DES) is based mainly on either analysis or synthesis approaches. In the synthesis approach, the design process starts from high level requirements which are then automatically refined to obtain lower abstraction levels. In this paper, we begin by introducing the two design approaches and defining the synthesis problem in DESs, and in protocols in particular. Then, we survey and assess some existing protocol synthesis methods. Then, we present two novel formal and systematic methods we have developed for the synthesis of DESs. The first method is used for the design of distributed systems which must satisfy some temporal constraints. The second method takes into account concepts such as controllability and observability, which are used in the control theory of DESs. Finally, we conclude and propose some future works.