What is the diff between "import" vs "include" ?

In a WSDL definition I saw an "import" af and *.xsd file and an "include" of an *.xsd schema.

what is the difference?

I assume that "include" just put the *.xsd text into the wrapping *.wsdl file.
No namespace overridings could take place.

Whereas in an "import" statement namespace overriding could take place.

Is this correct?

Are there any more diffs?

Ben