From Svg wiki

One of the more powerful features of SVG is the ability to communicate asynchronously with the server.

Some JavaScript methods to do this are:

• getURL: used to retrieve files or data using a HTTP_GET (see Adobe Extensions)
• postURL: used to save files or data using a HTTP_POST (see Adobe Extensions)
• XMLHttpRequest

Examples and Tutorials

• http://www.carto.net/papers/svg/postgis_geturl_xmlhttprequest/