Fragmentation is a problem. No solutions mentioned. A process consists of a segmented virtual address space and one or more threads. A process can only run on a machine whose kernel matches its host descriptor. To create a process, an execute-process request is sent to a kernel along with a descriptor for the process.
Processes control their address space explicitly.
An address space consists of segments. To add a new segment, a process can perform a map operation on a file-like object. The parameters needed by a map operation are the object's capability, the segment's virtual address and length. To remove a segment, a process can unmap the segment. The unmap operation returns the unmapped segment's capability which can then be reused by the same or another process.