Karl R. P. H. Leung

Location Estimation via Support Vector Regression

Location estimation using the global system for mobile communication (GSM) is an emerging application that infers the location of the mobile receiver from multiple signals measurements. While geometrical and signal propagation models have been deployed to tackle this estimation problem, the terrain factors and power fluctuations have confined the accuracy of such estimation. Using support vector regression, we investigate the missing value location estimation problem by providing theoretical and empirical analysis on existing and novel kernels. A novel synthetic experiment is designed to compare the performances of different location estimation approaches. The proposed support vector regression approach shows promising performances, especially in terrains with local variations in environmental factors

A Metamorphic Testing Approach for Online Testing of Service-Oriented Software Applications

Testing the correctness of services assures the functional quality of service-oriented applications. A service-oriented application may bind dynamically to its supportive services. For the same service interface, the supportive services may behave differently. A service may also need to realize a business strategy, like best pricing, relative to the behavior of its counterparts and the dynamic market situations. Many existing works ignore these issues to address the problem of identifying failures from test results. This article proposes a metamorphic approach for online services testing. The off-line testing determines a set of successful test cases to construct their corresponding follow-up test cases for the online testing. These test cases will be executed by metamorphic services that encapsulate the services under test as well as the implementations of metamorphic relations. Thus, any failure revealed by the metamorphic testing approach will be due to the failures in the online testing mode. An experiment is included. Copyright

Modeling Web navigation by statechart

There is a trend of increasing size of Web sites and increasing complexity of Web pages by dynamic content in recent years. Currently available Web navigation modeling tools are unable to cope with the need of modeling these contemporary Web sites, especially those with dynamic content. This need is analyzed in this paper and a Web navigation model based on the statechart is proposed to meet the requirements. The model will serve as a tool for modeling and analyzing navigation of complex and dynamic Web sites.

On the efficiency of domain-based COTS product selection method

Use of commercial-off-the-shelf (COTS) products is becoming a popular software development method. Current methods of selecting COTS products involve using the intuition of software developers or use a direct assessment (DA) of the products. The former approach is subjective, whereas the latter approach is expensive. This high cost is because the efficiency of the DA approach is inversely proportional to the product of the number of modules in the system to be developed and the total number of modules in the candidate COTS products. With the increase in the number of available COTS components, the time spent on choosing the appropriate COTS products could easily offset the advantages of using them. Neither of the selection approaches mentioned leads to quality results. Furthermore, inappropriately chosen COTS components may cause much greater damage to a development project than faults in software units that are developed in-house. A domain model is a generic model of the domain of an application system. It captures all of the features and characteristics of the domain. We have developed a new indirect selection approach, called the domain-based COTS product selection method, which makes use of domain models. We have successfully applied our selection method to the development of an on-line margin trading application. In this paper, we first analyze the efficiency of the domain-based COTS product selection method qualitatively. Then, we study the efficiency of the method by means of a formal approach and also through the case study of the on-line margin trading application. All of these results show that the domain-based COTS product selection method is more efficient than the DA methods. q 2002 Published by Elsevier Science B.V.

Towards a metamorphic testing methodology for service-oriented software applications

Testing applications in service-oriented architecture (SOA) environments needs to deal with issues like the unknown communication partners until the service discovery, the imprecise black-box information of software components, and the potential existence of non-identical implementations of the same service. In this paper, we exploit the benefits of the SOA environments and metamorphic testing (MT) to alleviate the issues. We propose an MT-oriented testing methodology in this paper. It formulates metamorphic services to encapsulate services as well as the implementations of metamorphic relations. Test cases for the unit test phase is proposed to generate follow-up test cases for the integration test phase. The metamorphic services invoke relevant services to execute test cases and use their metamorphic relations to detect failures. It has potentials to shift the testing effort from the construction of the integration test sets to the development of metamorphic relations.

Locating mobile stations with statistical directional propagation model

Recently, mobile location estimation is drawing considerable attention in the field of wireless communications. Among different mobile location estimation methods, the one which estimates the location of mobile stations with reference to the wave propagation model is drawing much attention. This approach, in principle, makes use of the most primitive property of wave propagation - signal strength, to perform location estimation. Hence this approach should be able to apply to different kinds of cellular network. We found out that in estimating mobile location with reference to signal strength, the azimuth gain of directional antenna and environmental factors can help to improve the accuracy. In this paper, we report our study of a directional propagation model (DPM) which enhanced the traditional propagation model with these factors. We experimented our model with 3,703 sets of real life data collected from a major mobile phone operator of Hong Kong. Results show that the DPM models have significant improvement over other existing location methods in terms of accuracy and stability.

Software development as a workflow process

It is a general consensus that automated support for software development is essential to harness the ever increasing complexity of todays software. Many software development models, tools, and environments have been introduced to address such a need; however they are usually methodology-specific and impose a rather authoritarian policy on the way software is developed. This paper advocates the use of workflow systems to enact the process of software development. Besides being more general and flexible, the workflow paradigm supports useful features lacking in other approaches. Also, it helps to reduce development complexity by allowing both the software development process and the software themselves to be captured using the very same paradigm. This paper introduces a workflow system being developed to support the software development process by presenting a solution to the ISPW-6 Software Process Example expressed in its specification language. This paper therefore serves two purposes: (1) to introduce a new and more general approach to software process enactment and (2) to identify new requirements for the workflow paradigm, such as event dependency, that are applicable to many other advanced applications.

Improvements towards formalizing UML state diagrams in CSP

The Unified Modelling Language (UML) includes a variant of state charts, called state diagrams (SD), for modelling systems with complex interactive behaviour. The official definition of UML specifies the abstract syntax of state diagrams without any formal semantics and hence is unable to perform formal system behaviour analysis. Various attempts have been made to provide such a formal basis for UML state diagrams. Among different attempts, the work reported in [Muan Yong Ng et al. (2003)] is formalizing SD in terms of communicating sequential processes (CSP). In this paper, we present some improvements upon the formalization. The improvements help clarify the semantics of UML SD and make the formalization more complete. Furthermore, we illustrate the use of CSP in reasoning about the equivalence of state diagrams and discuss the benefits of the formalization.

Multiple signature handling in workflow systems

In paper based workflow systems, signatures by individual or groups of people have been used extensively for various purposes. Currently there are many studies on computerizing workflow systems. Also there are studies on implementing signatures in electronic media. But the diversified purposes of a signature in workflow makes a straightforward implementation of digital signature schemes inadequate to satisfy the needs of an electronic workflow system. There are few studies on the implication on the purposes of signatures in workflow systems after the change in the media of operation. Signatures in workflows can be classified into two categories: single and multiple signatures. The paper reports on the purposes of multiple signature and our design for the implementation of these purposes with illustration using the Liaison workflow engine.

A workflow vista of the software process

Software development is a complex process for which automated tools for the management and the execution of the process are highly desirable. Existing tools often provide a sequence of phases to be followed and some mechanism for refining a phase into more detailed phases. However, derivations from the pre defined phases and the top down refinement approach cannot be easily accommodated without losing a significant amount of control. Such a static view of the software development process does not reflect the practice of system developers and hence is inappropriate for both the management and the execution of the process. The paper advocates a workflow based view to the software development process which provides elaborate control and supports dynamic organisation of the development phases. Equally important, the paper highlights the fact that the software process poses many requirements that are shared by other application domains. Hence, overcoming the challenge of providing workflow support to the software process will shed light on the problems in other application domains that are possibly less well understood.