基于构件的地理工作流框架:一个方法学的探讨

软件框架为特定领域的软件复用带来了便利.众所周知,软件框架开发的难度要大于开发一个普通可复用构件.采用支持黑盒复用的基于构件的软件框架概念,探讨了地理工作流框架的开发过程.一个地理工作流应用是地理信息领域的工作流管理系统,它可以通过复用地理工作流框架实现.从方法学的角度看,为了开发地理工作流框架,需要进行以下活动:领域分析、领域设计、框架设计和实现.其输出分别是识别了领域变化性的领域模型、领域特定的软件体系结构(DSSA)、软件框架产品.在地理工作流的上下文中,首先对领域变化性进行了识别和分类,包括空间数据类型、空间数据管理、空间操作、过程和空间数据表现5个方面的变化性,它们可以组织成树状视图.然后,为了处理上述变化性,设计了DSSA和框架的软件体系结构,其中前者是后者的模板,而框架体系结构采用HMB风格.最后,对地理工作流框架构件的开发以及框架复用进行了简单描述.与其他地理工作流系统相比,其优势在于由于框架扩展能力带来的灵活性.

A Component-Based Geo-Workflow Framework: A Discussion on Methodological Issues

Software framework (SF) brings forth lots of conveniences for software reuse in specific domains. It is well-known that a framework is much harder to be developed than a common reusable component. Based on the conception of component-based software framework (CBSF) that provides black-box reuse approach, a development process for geo-workflow domain is in discussion. A geo-workflow application is one sort of workflow management systems applied in the geographic information domain, and can be implemented through reusing component-based geo-workflow framework (CBGWF). From the methodological point of view, the following steps are necessary to develop a CBGWF: domain analysis, domain design, framework design and implementation. The outputs of them are domain models with identified variabilities, domain-specific software architecture (DSSA), and products of software framework, respectively. In the context of geo-workflow, domain variabilities, which are identified and classified first, involve variabilities of geospatial data types, variabilities of geospatial data management, variabilities of geospatial operations, variabilities of processes, and variabilities of geospatial data representation. These variabilities can be organized in a tree view. Then, using HMB style, DSSA and architecture of CBGWF are designed, where the former can be regarded as a template of the latter. Finally, the framework component development based on EJB component model and the reuse of CBGWF are described in brief. Compared with other geo-workflow systems, the main advantage consists in its flexibility caused by the extensibility of CBGWF.