Research On Software Architecture-based Composition Of Internetware

As Internet technologies advance, software execution platforms are changing gradually from traditional static and closed hosts to the open, dynamic and ever-changing Internet. Internetware, that is software running on such execution platforms, should be autonomous, evolvable, co-operative, polymorphic and context-aware, compared to traditional software. The distribution of abundant software assets over the Internet makes it a natural way to develop Internetware by composition; however, the open, dynamic and ever-changing Internet challenges the composition as well. The distribution of Internetware components implies that the composition of Internetware be achieved by dynamic linking; Autonomous Internetware components are usually treated as black boxes when they are involved in the composition. Besides, to make Internetware context-aware, developers should take into account possible changes that the target Internetware may confront and model necessary strategies to handle these changes. Moreover, the composition of Internetware is not done in only one move; instead, the ever-changing and rapid growing environment makes it more realistic to compose an Internetware application iteratively. Therefore, an efficient and effective approach to Internetware composition as well as the tool support is required.In this dissertation, the approach of architecture-based component composition (ABC) is applied to the composition of Internetware. A software architecture (SA) description language dedicated to the composition of Internetware is proposed to record the platform independent SA model (PI-SAM) of Internetware. Transformation rules are designed to transform a PI-SAM to platform specific SA models (PS-SAM), which represent the composition of reusable components. A visualized SA-based component composition tool is developed to facilitate the transformation process. The architecture description language (ADL) for Internetware composition is called ABC/ADL, which provides an accurate description of Internetware composition based on reusable components. ABC/ADL is XML-based and conforms to the classification and comparison framework for ADLs. It models the computation units in Internetware by components and models the interactions between components by connectors. The topology of the resulting composition is depicted by architectural configurations. Furthermore, to cope with the ever-changing execution platform for Internetware, traditional composite component in ADLs is extended to support a natural way to model strategies as responses to changes that an Internetware application may confront. The SA model for Internetware forms the basis of Internetware composition, the quality of which is ensured by the SA-based analysis and validation.SA-based Internetware composition is targeted at a platform specific Internetware application. Different platforms may provide different component execution mechanisms. To ensure the portability of an Internetware application, that is to construct an identical Internetware application based on different types of components easily, SA-based Internetware composition distinguishes two types of SA models, one is PI-SAM and the other is PS-SAM. More specifically, PI-SAM is used to capture business level structures of an Internetware application, and PS-SAM is used to record how platform specific components are composed to fulfill the application induced by the according PI-SAM. PS-SAM knows how to leverage platform specific mechanisms for better implementation of an Internetware application; it is actually an abstract description for a complete platform specific implementation and serves as the input for Internetware deployment. The Internetware composition is manifested as model transformation from PI-SAM to PS-SAM. This transformation involve three main activities. First, the concept mapping is setup between PI-SAM and PS-SAM. This mapping forms the basis of SA-based component reuse. Then topology conversion is required, when a PS-SAM does not present a hierarchical structure as the PI-SAM does. A quality attribute driven approach is proposed to flatten the hierarchical PI-SAM. Finally, the strategies in the PI-SAM for change handling would be implemented by platform specific supporting mechanisms. The model transformation rules embodied in these activities are elicited and used to transform a PI-SAM to a PS-SAM by linking reusable components and adding platform specific information to the PI-SAM. Such model driven composition ensures not only the portability of an Internetware application, but also the quality and efficiency of the Internetware composition.To facilitate the model transformation process for Internetware composition, a visualized SA-based Internetware composition tool, ABCTool, is developed. ABCTool is based on the open and popular Eclipse framework and uses ABC/ADL as its core data. It is capable of visual modeling of SA models for Internetware applications and transforming a PI-SAM to a PS-SAM. Specifically, ABCTool supports multiple views for the design and communication of an SA model; it allows hierarchical refinements for composite components as well as convenient mappings between the outer and inner interfaces of a composite component. Based on component repositories, ABCTool helps developers to compose effectively and efficiently reusable components to form an Internetware application, guided by its SA model.In a word, SA-based Internetware composition is a combination of the idea of SA design and the technologies of component-based software development. It supports effective and efficient Internetware composition under the open, dynamic and ever-changing execution platform in a model driven way. The feasibility and effectiveness of this approach, as well as the usage of ABCTool, is demonstrated by the composition of a comparison shopping mall based on existing applications.