Research On Dynamic Services Evolution Based On Services Collaboration Supported PaaS Platform

With the software and network technology develops to mature, the model of software delivery, application, product form and business model has made dramatic changes, the software has become a service (Software as a service, SaaS). Users no longer need to install any of the local software, they custom the software on-demand, update it online, need no maintenance, and use it with the rental business model which is for free or for subscription. SaaS as a delivery, deployment, operation and use patterns are astracting more and more attention and recognition. At the same time, the conception of Cloud Computing with the features of distribution and virtualization has promoted the rapid development of new type of software pattern architecture and related technology, it also provide a wider prospects for SaaS application, which makes the users customize the personalized SaaS services as possible. However, the promotion of SaaS services application process in Cloud Computing environment is facing a great challenge, namely the lack of unified support platform.For example, some existing SaaS applications can not well support the dynamic expansion and scale of tenants. But the design and implementation of the technology to support the multi-tenant properties is very comples, which seriously hindered the large-scale application and popularization of SaaS services.Therefore, a number of PaaS platform has realized to support SaaS application delivery and deployment. PaaS platform provides such a development, deployment, integration, design, storage, operating in one of the platform and environment. However, the current study for PaaS platforms are mostly concentrated in supporting the custom, delivery, use and deployment of a single application, they alll lack the support for collaborative applications, which do not meet the large-scale network applications' development trend of networking, collaboration and the cross-domain. Similarly, the technology of development, management and support such a large-scale collaborative applications are very complex, Therefore, in our paper, we promote a PaaS platform which support the services collaboration. This platform provide a new type of software pattern to support the development, delivery, deployment, customization and use of the collaboration of SaaS services. The services provider do not need to pay attention to the complex underlying implementation technology, they just need to focus their own services. With the variety of tools and technical support provided by the platform, we can build the collaborative applications in a quick and correct way.Based on the application mode above, the platform will bring together many professional software services resources which are the basis for building the collaborative applications.Industry service providers and integrators can arranged and combined these services to form form multiple cross-domain collaboration service, and the ultimately industry users can customize the services to meet their individual needs. However, the services deployed on the platform may come from different software providers, once a provider need to change the business process of one service, it would make some impacts on the collaboration and running of the collaborative application. We call this situation as the services dynamic evolution problem on PaaS platform which support the services collaboration.The services evolution problem needs to focus on such respects: 1. Impact of service evolution. The changes on one service not only impacts the application but also impact some other applications. How to compute this impact and how to assure the impact under the control become the key issue.2. Change propagation. When we change the process structure, we need to consider whether other collaborative applications may suffer the change impact. We also need to provide a automatic propagation technology.3. Running instances immigration. The services evolution occur in the execution of collaborative applications. Once the process schema migrates from the old pattern to the new one, the running instances under the old schema need to migrate to the new one, how to assure the correctness of immigration is the key issue.Therefore, we provide a PaaS architecture and description of the models of the platform. Then we solve the problem brought by the evolution of the applications in PaaS delivery platform such as the change impact analysis and automatically resolve application process change propagation depends on the impact of other issues, and the migration of running process instances. The main work of this paper are:1. The quantitative analysis of the distributed processes evolution of collaborative applications in PaaS platform. The processes evolution can be divided into many category such as the evolution of the process structure, protocol-driven business evolution, policy-driven and behaviour-driven evolution and the evolution of operational, the major concern of our paper is the structure evolution which is the most complex and most critical question. Under the collaborative environment, an change in one process structure of an application will impact other applications who depend on the application, how to describe the impact into a quantitatively number become the key issue, we provide an evolutionary effects analysis method which make the impact expressed in quantitatively and can limit and control the evolution in lower-cost range.2. We provide the change propagation method for the evolution of inter-process of distributed collaborative applications in PaaS platform. When the process of an application in distributed collaborative model need to change, it will affect other applications, how will other affected applications make the relative adjustment to realize the adaption as much automatically as possible become the key problem. We provide a range of operations of finite automata to complete the change propagation in an automatic way.3. We provide a on-line migration method for running instance of processes. When a process is changed from the old schema to the new one, running instances under the old model will face the problem that they may not continue to run correctly in the new schema, how to make a smooth migration of the old instance to the new model become the major problem. we use state of the path to find a way to determine the instance of the point and the migration path of the migration, so that dynamic migration of running instances.This research focus on the key techniques in the evolution of distributed collaborative processes of applications in PaaS delivery platform which provide the guide for the entire life cycle of service processes and has a wide application prospects.