採用Web技術整合GIS與通用性資料庫應用系統之研究–以海事地理資訊系統為例

Abstract

在交通監控中心裡為使管制員充分掌控交通狀況，其管理工作站一般配置兩台螢幕，一台螢幕專供顯示地理資訊圖像外，另搭配一台螢幕顯示其相關的資訊信息。為降低開發與維護成本，資訊服務業者都期望能發展出一套通用性資訊系統，可適用於不同硬體平台、作業系統甚至國家語言等。現今Web技術如Java、瀏覽器的發展宗旨即在實現跨平台的理想，然而因其受限於HTTP架構（Request →Process → Reply），與交通監控管理的作業模式並不相符。在監控模式下，是由伺服器端主動通知客戶端事件的發生或改變；這與Web模式下由客戶端提出交易請求再獲得結果的方式相異。因此想在目前的HTTP架構下，採用Web技術來發展通用性的監控管理資訊系統極為困難。

在這篇論文裡，我們提出了五項規範來衡量資訊系統是否已符合通用性要求，這五項規範分別為：硬體獨立性、作業系統獨立性、使用語言獨立性、資料庫工具獨立性及應用系統獨立性。為符合這五項通用性規範，本系統仍採用Java技術作為開發平台，並結合Web主動推播技術來解決監控管理系統下需能獲取即時資訊的問題；使得工作站上，Web化監控管理資訊終端能與地理資訊終端相互傳遞訊息。此外，我們探討如何以RIA (Rich Internet Application) 技術來開發網頁程式，以改善系統反應效率及讀取記錄時網頁需重刷新的缺點，使得操作畫面感覺與傳統桌面程式相同。最後，為了驗證通用性資訊系統，除發展三種不同語文套件外，我們將完成的實作系統在不修改程式碼的情況下，觀察其於不同的硬體、作業系統、資料庫工具及使用者語言間的執行情形，以確定通用性資訊系統的開發可行性與效益，達到降低軟體開發與維護成本的目的。

In a Traffic Service Center, for the purpose of easily monitoring traffic status, operator can supervise the condition through a traffic monitoring station. In general, there are two monitors in a traffic monitoring station. One monitor dedicates to be a GIS client that can display a electronic chart overlapped with moving targets. Another is a DB client to display corresponding text information. To save the cost of development and maintenance, usually the software developers wish to build a generic information system that can run on a variety of environment over different hardwares, OS and user languages. Web technology nowadays such as Java and browser-based application can achieve this goal, but do not fully satisfy the characteristics of a monitoring system. In HTTP protocol, the scenario is request, process and reply. This is different from the model of a monitoring system. For a monitoring system, server will notify clients whenever an event occurs or changes. On the other hand, a HTTP client can have a reply only after its previous request. For this reason, it seems difficult to build a generic information system by adopting Web technology.

In this thesis we propose five criteria that can evaluate whether an information system is generic or not. These criteria are: hardware independence, OS independence, user language independence, database tool independence and application independence. To meet the above criteria, we adopt the Java technology as the development and run-time platform for the implemented system in this thesis. In addition to this, we utilize web push technology to achieve the real-time data acquisition in a monitoring system. Based on this push technology, web DB client can send data to GIS client and receive from it. Meanwhile, we study how to develop the browser-based program by using RIA (Rich Internet Application) technology. With RIA technology, the system response time is improved and there is no need to refresh a whole web page while a user asks for a new data record. As a result, the look and feel inside a browser-based client with RIA is almost the same as a traditional C/S database client. At last, to validate the development possibility of a generic information system, we have tried to run our developed system under a variety of hardwares, OS, database tools and logon with different user language. From the experimental result, we believe this development model is workable to a generic information system and it can dramatically save the cost and improve the software development and maintenance of GIS system.