What's the significant improve from UML 2.0 to UML 1.4?

BTW,what's the latest version of UML,and how o开发者_运维知识库ften does it release a new version?

As far as I'm aware there's no regular release schedule. As for the differences between versions, you can find a summary for example here, probably a bit more readable here.

The latest version of UML is UML 2.2 which is built on the top of xmi 2.1. See more at: http://www.eclipse.org/modeling/mdt/?project=uml2

What's the significant improve from UML 2.0 to UML 1.4?

The site uml-diagrams.org present a comprehensive summary of changes from version to version. As it's a bit long for a quote, I won't quote the answer, and let people read it on the above link.

BTW,what's the latest version of UML

Depens on the point of view. At the time of writing, the latest ISO approved is UML 1.4.2 (2005), the latest OMG final is UML 2.4.1 (2011) and the latest OMG published is UML 2.5 (2012 - 2013).

and how often does it release a new version?

I know ISO as some timing requirement, but I don't know any for the OMG. UML is continuously evolving with so called “minor updates”.