XML IDE on Linux

I am looking for a good XML IDE on Linux, which can support editing XML
Schema and some other existing XML standards, like WML, VoiceXML, and so
on. I am pretty familiar with XML Spy, which is based on MS Windows. I'd
like to find any tools like it, which can provide multi-views for XML
documents, especially for XML Schema. The free software is highly
prefered.

Any recommendations?

Thanks.

Shen