在WebGIS的快速发展过程中,其架构方法和实现技术的研究一直是人们关注的热点。本文针对传统WebGIS开发复杂度高、交互体验性贫乏、运行效率低等不足,在对RIA/SilverLight和REST技术的研究基础上,以整体结构模块化,开发行为统一化,代码可复用及经验可复用的指导思路下,提出由空间数据服务器(数据访问层DAL)、GIS服务和Web服务服务器(业务逻辑层BLL)及部署有SilverLight插件的浏览器(表现层UI)组成的3层架构式富网络地理信息系统,并阐述了数据层中空间属性数据库的设计和建立步骤以及优化经验,分析了业务逻辑层的构成和运行机制,为提高系统开发效率使用MVVM(Model-View-View Model,模型－视图－视图模型)设计模式,将表现层分为前端用户界面和后台逻辑两部分,并描述了用户熟悉的Office Ribbon设计样式的开发方法,说明了后台逻辑架构组件各自功能及通讯路径。最后,为验证此框架能够有效提高系统开发效率、丰富用户体验和改善系统运行性能表现等优势,利用SilverLight(C#)实现了应用实例——LightGIS。系统开发和运行实验表明,该框架能够很好地达成以下目的:(1)实现优美的用户操作界面和丰富的互操作性体验;(2)提供平滑、流畅的地图服务和高响应性空间分析;(3)具备优秀的系统可扩展潜力和可配置性。
The architecture and implementation technique of WebGIS are always the focus of scholars in its rapid developing process. Aiming at disadvantages of high complexity,poor interactive experience,and low response efficiency in "traditional" WebGIS application,this paper proposes a rich WebGIS application framework based on RIA/SilverLight and REST technologies which was divided into data access layer(DAL),business logic layer(BLL) and user interface layer(UI). Silverlight is an application framework for creating and delivering rich internet applications (RIA) and media experiences on the Web,which combining with the representational state transfer (REST) software architecture style can significantly remedy these shortages of "traditional" WebGIS application mentioned above. Firstly,in this paper the detailed description on designing and building steps of spatial databases were given,and the optimization experiences on spatial database were shared. Then the composition of business logic layer and its operating mechanism had been analyzed. To improve the efficiency of the user interface layer,the Model-View-ViewModel (MVVM) architectural pattern had been adopted. And to follow the user's habit,the office ribbon style had been used visually. The code-behind was programmed with.NET C#,and according to different function types,it was designed into event center component,configuration management component,UI interactive component,map container component,control management component,auxiliary function component,and the event center component is the communication hub. Finally,based on this framework,a rich WebGIS application which named LightGIS had been developed. It showed that the applied framework can effectively improve the efficiency,enrich user’s experience and enhance the system capability.
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