I really dont know in what context the above statements are defined.
Please refer opencl spec for any technical stuff.
Imagine you have a kernel declared like: testkernel(global float *array)
And you have an OpenCL buffer allocated for that float array.
Then you can't call the kernel like testkernel(&buffer).
On OpenCL you have to send a reference to the whole buffer (that's the only way right now), and specify the '15' offset manually with a constant parameter in the kernel's parameter list.
I guess OpenCL 2.0 will have an answer for this in the future.