Caspar Ryan

Coupling Metrics for Predicting Maintainability in Service-Oriented Designs

Service-oriented computing (SOC) is emerging as a promising paradigm for developing distributed enterprise applications. Although some initial concepts of SOC have been investigated in the research literature, and related technologies are in the process of adoption by an increasing number of enterprises, the ability to measure the structural attributes of service-oriented designs thus predicting the quality of the final software product does not currently exist. Therefore, this paper proposes a set of metrics for quantifying the structural coupling of design artefacts in service-oriented systems. The metrics, which are validated against previously established properties of coupling, are intended to predict the quality characteristic of maintainability of service-oriented software. This is expected to benefit both research and industrial communities as existing object-oriented and procedural metrics are not readily applicable to the implementation of service-oriented systems.

Cohesion Metrics for Predicting Maintainability of Service-Oriented Software

Although service-oriented computing (SOC) is a promising paradigm for developing enterprise software systems, existing research mostly assumes the existence of black box services with little attention given to the structural characteristics of the implementing software, potentially resulting in poor system maintainability. Whilst there has been some preliminary work examining coupling in a service-oriented context, there has to date been no such work on the structural property of cohesion. Consequently, this paper extends existing notions of cohesion in OO and procedural design in order to account for the unique characteristics of SOC, allowing the derivation of assumptions linking cohesion to the maintainability of service-oriented software. From these assumptions, a set of metrics are derived to quantify the degree of cohesion of service oriented design constructs. Such design level metrics are valuable because they allow the prediction of maintainability early in the SDLC.

The Impact of Service Cohesion on the Analyzability of Service-Oriented Software

Service-Oriented Computing (SOC) is intended to improve software maintainability as businesses become more agile and underlying processes and rules change more frequently. However, to date, the impact of service cohesion on the analyzability subcharacteristic of maintainability has not been rigorously studied. Consequently, this paper extends existing notions of cohesion in the Procedural and OO paradigms in order to account for the unique characteristics of SOC, thereby supporting the derivation of design-level software metrics for objectively quantifying the degree of service cohesion. The metrics are theoretically validated, and an initial empirical evaluation using a small-scale controlled study suggests that the proposed metrics could help predict analyzability early in the Software Development Life Cycle. If future industrial studies confirm these findings, the practical applicability of such metrics is to support the development of service-oriented systems that can be analyzed, and thus maintained, more easily. In addition, such metrics could help identify design problems in existing systems.

A Controlled Experiment for Evaluating the Impact of Coupling on the Maintainability of Service-Oriented Software

One of the goals of Service-Oriented Computing (SOC) is to improve software maintainability as businesses become more agile, and thus underlying processes and rules change more frequently. This paper presents a controlled experiment examining the relationship between coupling in service-oriented designs, as measured using a recently proposed suite of SOC-specific coupling metrics and software maintainability in terms of the specific subcharacteristics of analyzability, changeability, and stability. The results indicate a statistically significant causal relationship between the investigated coupling metrics and the maintainability of service-oriented software. As such, the investigated metrics can facilitate coupling related design decisions with the aim of producing more maintainable service-oriented software products.

Comparing the impact of service-oriented and object-oriented paradigms on the structural properties of software

Service-Oriented Architecture (SOA) is a promising approach for developing enterprise applications. While the concept of SOA has been described in research and industry literature, the techniques for determining optimal granularity of services and encapsulating business logic in software are unclear. This paper explores this problem using a case study developed with two contrasting approaches to building enterprise applications that utilise services, where one of the approaches employs coarse-grained services developed based on the principles of Object-Orientation (OO), and another approach is based on embedding business rules and logic into executable BPEL scripts and constructing a system as a set of fine-grained services. The quantitative comparison based on a set of mature software engineering metrics showed that a system developed using the BPEL-based approach has a potentially higher structural complexity, but at the same time lower coupling between software modules compared to an OO approach. It was also shown that some of the existing software metrics are inapplicable to SOA, hence new metrics need to be developed.

Software, performance and resource utilisation metrics for context-aware mobile applications

As mobile applications become more pervasive, the need for assessing their quality, particularly in terms of efficiency (i.e., performance and resource utilisation), increases. Although there is a rich body of research and practice in developing metrics for traditional software, there has been little study on how these relate to mobile context-aware applications. Therefore, this paper defines and empirically evaluates metrics to capture software, resource utilisation and performance attributes, for the purpose of modelling their impact in context-aware mobile applications. To begin, a critical analysis of the problem domain identifies a number of specific software, resource utilisation and performance attributes. For each attribute, a concrete metric and technique of measurement is defined. A series of hypotheses are then proposed, and tested empirically using linear correlation analysis. The results support the hypotheses thus demonstrating the impact of software code attributes on the efficiency of mobile applications. As such, a more formal model in the form of mathematical equations is proposed in order to facilitate runtime decisions regarding the efficient placement of mobile objects in a context-aware mobile application framework. Finally, a preliminary empirical evaluation of the model is carried out using a typical application and an existing mobile application framework

Adaptive application offloading using distributed abstract class graphs in mobile environments

Self-adaptation of software has been used as a mechanism to address complexity and constraint in mobile and pervasive computing environments. Adaptive offloading is a software adaptation mechanism in which an application dynamically distributes portions of itself to remote devices to achieve context specific optimizations. The feasibility of using adaptive offloading in pervasive environments is determined by the computational efficiency of adaptation algorithms and the efficacy of their decisions. However, existing state-of-the-art approaches incur overheads from storing, updating and partitioning complete application graphs on each device, which limits their utility and scalability in resource constrained mobile environments. Hence, this paper presents a novel distributed approach to application representation in which each device maintains a graph consisting only of components in its memory space, while maintaining abstraction elements for components in remote devices. This approach removes the need to store and update complete application graphs on each device and reduces the cost of partitioning an application during adaptation. In addition, an extension to an existing application graph partitioning heuristic is proposed to utilize this representation approach. An evaluation involving computationally heavy open-source applications adapting in a heterogeneous collaboration showed that the new approach reduced graph update network cost by 100%, collaboration-wide memory cost by between 37% and 50%, power usage by between 63% and 93%, and adaptation time by between 19.47% and 98%, while improving efficacy of adaptation by 12% and 34% for two of the considered applications.

Application Adaptation Through Transparent and Portable Object Mobility in Java

This paper describes MobJeX, an adaptive Java based application framework that uses a combination of pre-processing and runtime support to provide transparent object mobility (including AWT and Swing user interface components) between workstations, PDAs and smartphones. Emphasis is placed on the mobility subsystem (MS), a mobile object transport mechanism providing a high level of transparency and portability from the perspective of the system and the developer. The MS is compared to its most similar predecessor FarGo, demonstrating the advantages of the MS in terms of transparency and portability. Furthermore, a series of laboratory tests are conducted in order to quantify the runtime performance of the MS and two other systems, FarGo and Voyager.

The impact of software development strategies on project and structural software attributes in SOA

Service-Oriented Architecture (SOA) is a promising approach for developing integrated enterprise applications. Although the architectural aspects of SOA have been investigated in research and industry literature, the actual process of designing and implementing services in SOA is not well understood. The goal of this paper is to identify tasks needed for successful design and implementation of services, and investigate their effect on the project and structural software attributes in the context of SOA. This facilitates the specification of guidelines for decreasing the required development effort and capital cost of the SOA projects, and improving the structural software attributes of service implementations. The tasks are identified in the context of top-down, bottom-up and meet-in-the-middle software development strategies.

A Formal Model of Service-Oriented Design Structure

Service-oriented computing (SOC) is a promising paradigm for developing enterprise software systems. The initial concepts of service-orientation have been described in the research and industry literature and software tools for assisting in the development of service-oriented (SO) applications are becoming more widely used. Nonetheless, a precise description of what constitutes a SO system is yet to be formally defined, and the design principles of SOC are not well understood. Therefore, this paper proposes a formal mathematical model covering design artefacts in service-oriented systems and their structural and behavioural properties. This model promotes a better understanding of SO concepts, and in particular, enables the definition of structural software metrics in an unambiguous, formal manner. Finally, although the proposed model is generic, it can be customised to support particular technologies as shown in this paper where the model was tailored for BPEL4WS implementation.