Yukyong Kim

The service modeling process based on use case refactoring

Service-Oriented Architecture (SOA) is an architecture for a system or application that is built using services that implement business functionality with proper granularity. If the granularity of a service is finer, the flexibility and reusability of the service is lower. Therefore, it is critically important to identify what pieces of functionality will become services and to define the interfaces of those services. In this paper, we define a process to identify services by use case refactoring. Task trees are defined to restructure use cases, and five refactoring rules are introduced along with a running example. Because this modeling process can choose the correct levels of abstraction and granularity, it can be helpful in identifying coarse-grained services.

Adaptable Web Services Modeling Using Variability Analysis

Web services have recently come into focus as they are able to make software systems flexible, reusable, and cost-effective. In distributed Web services environments, Web services should be very adaptable because the potential number of services can be extremely large and target consumers and service providers have to face various circumstances. To promote the adaptability of services, the variability on Web services should prudently be considered and modeled. In this paper, we present a method for modeling highly adaptable Web services by analyzing the variability with respect to architectural and behavioral features. We define modeling aspects of Web services to extract the variability and variation points. We focus on the modeling of variability of Web services from variation points of structural features and behavioral features. In this work, we try to describe how adaptable Web services are developed with a suitable description of the variability as a technique for customizing systems based on Web services.

A Trust Type Based Model for Managing QoS in Web Services Composition

Given the distributed, heterogeneous nature of Web services, the availability and reliability of Web services is uncertain. Moreover, service providers may have varying levels of quality. A way to understand and manage the quality attributes is needed. In this paper, we present an approach for the dynamic composition of Web services with quality of services (QoS) attributes. We adopt a concept of mediator to select credible services for service requestors. In our model, mediators evaluate services and assign trust ratings. A mediator includes a multi-dimensional quality model based on a set of non-functional properties that are transversal to all Web services, for example, their cost and reliability. In particular, we use the trust type inference rule to rate the trustworthy for selecting services optimally. Based on the QoS model, we present dynamic service selection approach to select and aggregate services to satisfy users QoS requirements. This approach can be used to prune services that would be composed and thus avoid service composition execution plans that would be unacceptable to service requestors.

Formal Identification of Right-Grained Services for Service-Oriented Modeling

Identifying the right-grained services is important to lead the successful service orientation because it has a direct impact on two major goals: the composability of loosely-coupled services, and the reusability of individual services in different contexts. Although the concept of service orientation has been intensively debated in recent years, a unified methodic approach for identifying services has not yet been reached. In this paper, we suggest a formal approach to identify services at the right level of granularity from the business process model. Our approach uses the concept of graph clustering and provides a systematical approach by defining the cost metric as a measure of the interaction costs. To effectively extract service information from the business model, we take activities as the smallest units in service identification and cluster activities with high interaction cost into a task through hierarchical clustering algorithm, so as to reduce the coupling of remote tasks and to increase local task cohesion.

Trust Type Based Semantic Web Services Assessment and Selection

As multiple service providers make themselves available on-line, the trustworthiness of services becomes significant. In Web services environments, services from different providers might have to be combined to establish a complete service. Although the individual service can be trusted, the composed service is not guaranteed against trust. Thus there must be a way to determine the composed service is trusted. This paper presents a trust type model to deduce the trust level of composed services. Then, we present a conceptual framework which enables trust based service discovery and selection. Using the inferred trust type of the composed service as the weight, we can evaluate service candidates and select the best match of them. Finally we describe the experiment results to validate our QoS based service selection.

Pragmatic granularity decision for right-grained services in service-oriented modelling

The identification of right-grained services is important in leading a successful service orientation because it has a direct impact on two major goals: the composability of loosely-coupled services and the reusability of individual services in different contexts. Although the concept of service orientation has been intensely debated in recent years, a unified methodic approach for identifying services has not yet been identified. In this paper, we suggest a formal approach to identify services at the right level of granularity from the business process model abstraction. Our approach adopts the concept of activity allocation based on the locality principle for defining loosely-coupled services. The method utilising the concept of graph partitioning can minimise the network roundtrip costs incurred during the service execution. If we can define activities into a service as cohesively as possible, we can identify the reusable and self-contained services so as to reduce the coupling of remote tasks and increase the local task cohesion.

A Trust Management Model for QoS-Based Service Selection

As the number of available services increases on the Web, it becomes greatly vital in service-oriented computing to discover a trustworthy service that best fits users’ requirements. Once a set of services fulfilling user’s functional requirements are founded, one of these services invoked by the users depends mostly on the Quality of Services (QoS), particularly security, trust, and reputation. This paper proposes a trust management model to support service discovery and selection based on trust and QoS. We propose a novel trustworthy service discovery and selection mechanism to make service consumers get trustworthy services possible. The mechanism uses consumers’ feedback to describe service’s and service provider’s trustworthy level. The service selection using the quantitative measurement rather than consumers’ intuitive selection allows selecting a high reliable service accomplishing their quality requirements well. Finally, we give experimental results by implementing the prototype for verifying the trust evaluation method.

Use-case driven service modelling with XML-based tailoring for SOA

A key problem in service-oriented computing is how to extract business requirements and build solutions with available services. The manual process of eliciting business requirements from use cases and scenarios is time consuming. This paper proposes a semi-automatic way of deriving service models from business use cases using XML-based use-case tailoring. By matching the required capability of each use case to the available capabilities provided by services, the optimal set of use cases is realised by the appropriate set of services. We rewrite use cases in XML to achieve the clear separation of any semantic parts of use-case descriptions from visual representations. The resulting use cases are subsequently tailored into well-defined business functionalities, which are built as services according to service orientation principles. Finally, we analyse and discuss validation results of a case study to illustrate how the proposed approach works.

An approach to modeling context-adaptable services

Since users want to have proper services in their own position and surrounding circumstance in ubiquitous computing, it is critically important to provide appropriate services by adapting changes of the user requirements and their environments. Most approaches lack considerations for position or preference of users. In this paper, we present an adaptation process model to dynamically select services based on users preferences according to their contextual changes. We define a conceptual context model and use the adaptation process model to select proper services. The adaptation process consists of the service selection and the service negotiation. Service candidates are selected based on users and service providers preferences in the service selection process. The service negotiation process determines the best service among service candidates.