Research On Some Key Issues In Model And Model Transformation Approach In Model-Driven Architecture

In the realm of software engineering, we are witnessing an increasing momentum towards the use of models for developing software systems. This trend commonly referred to as Model-driven Software Development (MDSD), emphasizes on models as the primary artifacts in all phases of software. Model transformation is the core of MDSD, object code or Platform Specific Model (PSM) can be converted through a series of abstract Platform Independent Model (PIM).Years of theory and practice shows that the combination of model-driven ideas and software development is successful. This method can accelerate the process of software development, solve the problem with frequent change of business requirement, and meanwhile narrow communication risk of users. The developers may more focus more on the business analysis and models ignoring the implementation.The key problem of MDSD is how to describe models and transform models to target codes. Our works take software development of B/S patterned Web Management Information System (MIS) as the background, to overcome the drawbacks of current model and model transformation techniques. First, a platform independent business model (PIM-BM) with the simplification and extension of UML metamodels and a platform specific business component model (PSM-BC) are proposed. The version control methods of these models are also presented. And then a hybrid model transformation approach that supports model synchronization based on the revision number of models is presented, which can transform the PIM-BM to PSM-BC, and finally to usable system. At last, a model-driven rapid development platform is designed to verify all the above methods and technologies. Our contributions are listed as follows:(1) In order to improve the usability and precise semantics of UML, platform independent business model (PIM-BM) is proposed based on extension of UML metamodels. Compared with UML, this business entity-centered model has rich semantics. Its metamodel is extended based on the UML metamodels, removing some metamodels that are not related to MIS. PIM-BM is made up of business entities, the associations of entity and the actions of entities. In addition, the association of model elements in PIM-BM is also presented. That can guarantee that the relation is not lost during the process of model transformation. (2) After the extraction and analysis of some features from target platform applications, a novel platform specific business component model (PSM-BC) is proposed, synthesizing multiple application frameworks. The description, presentation and storage of this model are oriented to the features of target platform. PSM-BC defines business process object, business object and business presentation object. Once the requirements have been gathered, the web application is modeled from three points of view in order to reduce the complexity of models:business process layer, business object layer and business presentation layer. Theses models capture a comprehensive description of the web application. Models in different tiers are relatively independent with specific responsibilities and loosely coupled structure. A separation of design concerns into distinct model layers has several advantages such as ease of maintenance and standardization, the ability to select specialized tools and techniques for specific concerns. Each model in different layers is generated into a fine-grained component of the final system.(3) A general version control approach for the management of PIM-BMs and PSM-BCs is proposed. The content repository concept is first introduced in the storage of models. The model element and model association is taken as the node of the content repository. It will provide a new way of ideas for the researchers on the version control of models and the new application of the content repository.(4) A hybrid model transformation approach is presented based on PIM-BM and PSM-BC. The descriptive mapping rules are using QVT Relations language. This rule is relatively succinct and effective, supporting complex pattern matching of model elements. The whole process of model transformation can is simplified as the execution of rules in sequential order. In addition, the PSM-BCs to the target language is converted using the textual template evolution. In order to improve the reusability of template, the templates are designed as different plugins, which is the mapping rule from PSM-BC to the target language. This hybrid model transformation approach has certain promoting and enhancing effect and enriching the formalizing model driven development approaches.On the other hand, mixed usage of PIM-BMs and PSM-BCs often cause the inconsistency of models. a model synchronization approach based on the version of models for this problem is proposed. A subsequent model transformation only creates the target models if they are missing on the first execution. When any of the source models are modified and the transformation is executed again, the necessary changes to the target are determined and applied. At the same time, the target elements that can be preserved are preserved. This model synchronization approach reduces the amount of models that need subsequent model transformation.(5) And this paper implements a model-driven rapid development platform (MDARapid) for MIS, which verifies the above models and model transformation approach. This platform is used to generate the corporation’s business applications, including the maintenance of business data and other complicated business. It is especially fast, normative and efficient in the development of large application. This model transformation approach supported model synchronization has generated some real enterprise applications. For example, it has generated Natural Science Foundation Management System of Shandong Province of China (http://www.sdnsf.gov.cn/sdnsfms). This system has been successfully distributed with about ten thousand projects and project progress reports. There are hundreds of people online handling official business with this application. The distribution and uninterrupted running of the generated applications proves that our approach is feasible in practice.