Using SVG to Publish Graphics in Electric Power Information Management System

[Abstract]

In Power Information Management System, the needs of representing graphic information and providing integrated, spatially-refrenced data for all user throughout the Power company force the development of AM(Automated mappig) /FM(facility management) functions . During the developing , vector graphics of maps and associated information are always stored in database according to a private format defined based on application requirements .

Along with the developing of Internet/Intranet, the system should be implemented on WEB. With the demanding of displaying graphics on Internet Browser, variant solutions are brought out, such as Imagemap, ActiveX technology, Java applet technology and so on. After analysing the advantages and disadvantages of above methods, we decided to use SVG technology to publishing graphics on the Internet. SVG enables us to create dynamically generated, high-quality graphics from real-time data with precise structural and visual control, and it's open DOM interface enables us to perform our special professional functions on it.

Basically, we have performed following functions on Internet/Intranet:

The solution details will be described in this article.

1. SVG file generator Server

A SVG file generator Server is deployed between Web Server and database server. It's main task is converting graphic data in the database to a standard SVG file which can be published on the Internet by web server.

The most important requirments for the server are followings :

2. transforming to SVG format

It is so easy to transform the basic shapes such as line, rectangle,etc to SVG format because we have defined graphic data as vector graphics in our system.

In electric power graphic system, a marker is used to denote a symbol of a special type of power facility. In SVG format, the "symbol" element can be used to replace the marker in our graphics format. But the different state of a marker cannot help but to be presented using different symbol element in SVG format.

The coordinate in our map is different from the initial viewport coordinate system in SVG . The "transform" attribute should be used accordingly to "g" element and "text" element and "symbol" element in coordinate system transformations to achieve a correct map.

3. Interactive graphics on the client side

The client (Internet Browser) will receive a HTML file in which a SVG file embed. As the HTML file's contents are viewed using native browser capability, the SVG file is viewed using a SVG View plug-in (such as Adobe SVG Viewer) that must be installed on the client. Browse,pan and zoom functions have be done by SVG viewer.

Scripts being executed on the client side in browser provide users professional functions on the map in Browser. SVG DOM interface enable scripts to control the graphic elements to change with the data received from server and dynamic information is presented in dynamic graphics.

By combining SVG with existing Web technologies like HTML, JavaScript, DOM (Document Object Model), interactive graphics are created and special web applications can be implemented such as controlling the layers's visibility, answering the interactive operations events on the SVG map, requesting facility information to the Web Application Server and present the dynamic changes on graphics, requesting quasi-real-time data and presenting it on the SVG map and so on.