Context-aware Dynamic Personalised Service Re-Composition in a Pervasive Service Environment

A pervasive environment needs to take account of a user’s context and preferences in determining which services to provide to the user. Moreover, one of the important features of a pervasive service environment is its dynamic nature, with the ability to adapt services as the context of a user changes, e.g. as he/she moves around. This paper describes how these requirement changes can be sufficiently accounted for by using a personalisation component to ‘decide’ what a user needs, and a composition component to continuously monitor services and the changes associated with them. The paper presents how services can be recomposed dynamically if the changes in context require it. This approach has been incorporated into a platform to support pervasive services. The service composition process used is described, and the way in which personalisation is incorporated into this process is shown. Finally the paper provides a brief account of two prototypes built as a proof of concept for these ideas

An Investigation into Dynamic Web Service Composition Using a Simulation Framework

[Motivation] Web Services technology has emerged as a promising solution for creat- ing distributed systems with the potential to overcome the limitation of former distrib- uted system technologies. Web services provide a platform-independent framework that enables companies to run their business services over the internet. Therefore, many techniques and tools are being developed to create business to business/business to customer applications. In particular, researchers are exploring ways to build new services from existing services by dynamically composing services from a range of resources. [Aim] This thesis aims to identify the technologies and strategies cur- rently being explored for organising the dynamic composition of Web services, and to determine how extensively each of these has been demonstrated and assessed. In addition, the thesis will study the matchmaking and selection processes which are essential processes for Web service composition. [Research Method] We under- took a mapping study of empirical papers that had been published over the period 2000 to 2009. The aim of the mapping study was to identify the technologies and strategies currently being explored for organising the composition of Web services, and to determine how extensively each of these has been demonstrated and assessed. We then built a simulation framework to carry out some experiments on composition strategies. The rst experiment compared the results of a close replication of an ex- isting study with the original results in order to evaluate our close replication study. The simulation framework was then used to investigate the use of a QoS model for supporting the selection process, comparing this with the ranking technique in terms of their performance. [Results] The mapping study found 1172 papers that matched our search terms, from which 94 were classied as providing practical demonstration of ideas related to dynamic composition. We have analysed 68 of these in more detail. Only 29 provided a `formal' empirical evaluation. From these, we selected a `baseline' study to test our simulation model. Running the experiments using simulated data- sets have shown that in the rst experiment the results of the close replication study and the original study were similar in terms of their prole. In the second experiment, the results demonstrated that the QoS model was better than the ranking mechanism in terms of selecting a composite plan that has highest quality score. [Conclusions] No one approach to service composition seemed to meet all needs, but a number has been investigated more. The similarity between the results of the close replication and the original study showed the validity of our simulation framework and a proof that the results of the original study can be replicated. Using the simulation it was demonstrated that the performance of the QoS model was better than the ranking mechanism in terms of the overall quality for a selected plan. The overall objectives of this research are to develop a generic life-cycle model for Web service composition from a mapping study of the literature. This was then used to run simulations to replicate studies on matchmaking and compare selection methods

Model-driven and Compositional Service Creation in the Internet of Services

Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 2012In the Future Internet, billions of devices will be connected to the Internet. Devices at any levels of hierarchy provide software functionality that can be used by others. We can call the device’s functionality a service, which in turn, introduces the concept of the Internet of Services. From the software developer perspectives, a new service can be created by utilizing services in the Internet of Services. An important issue of the creation of such service-based application is regarding their deployment method on personalized and embedded devices. For each device with different capability and configuration, different tailored code is required. For this, a flexible method and tools that support an automatic code generation for a device with a specific capability and configuration are mandatory. This thesis proposes PMG-pro (Present, Model, Generate and provide), a language- independent, bottom-up and model-driven method for the service creation in the Internet of Services. With this method, a service is created by providing the new functionality of a service-based application as a service. By using existing service frameworks and APIs, from a service description, PMG-pro generates an abstract graphical service representation (service model) and source code implementing for service invocations. Depending on the target modeling languages, different graphical notations can be used to represent services. Similarly, different programming languages can also be used to implement the service invocations. We call these pairs (i.e., the service model and the source code) platform-specific models. With these platform models, service composers use the graphical service representation to model new service-based applications, while the machine (i.e., computer system) uses the source code to generate code from the service-based application model. This thesis contributes to the service engineering method that applies a modeldriven development approach. Three main contributions are a model-driven method for service creation, an automatic service presentation of pre-made services, and a new method of handling device capability and configuration. With these, service creation in the Internet of Services can be done in a rapid and automatic manner. Service designers can create a new service by defining a model of service-based applications using pre-made service models, while code for a specific device can be generated automatically from the model. The PMG-pro method has been partly prototyped and validated on various case studies in the domain of smart homes that have produced encouraging results. The method promotes a rapid, language-independent, and unified process of software service development