The workspace in diagram below flows to a stream.

I’ve added a build definition which builds from this workspace.
If I deliver change sets from a different workspace to the stream in diagram should these change sets be built when I perform a build ? Do the change sets need to be first accepted into the workspace from the stream before they are built ?
Currently when I perform a build the change sets(which have been delivered to the stream from a different workspace)
are not being delivered to the workspace in diagram and so are not being built.
It depends how your build definition is configured:
As this thread mentions:
But with a BuildForge-based Build Definition, as mentioned in “Rational Team Concert 3.0 and Build Forge: An integration scenario“: