Answer the following questions. For questions asking for short answers, there may not necessarily be a "right" answer, although some answers may be easier to justify. Finally, write your answers using complete sentences and paragraphs — don't be sloppy in expressing your answers.
Support your answers with material from the papers (e.g., a quote of a phrase or sentence), or with your own critical arguments, as appropriate (the Lampson protection paper is fair game). I am interested in your justifications as much as the answer itself — and the more often you can quote from a paper, the less you have to justify. For instance, two possible answers to part (a) for Hydra are:
A protection domain in Hydra is the "local name space" (LNS). An LNS represents the current set of objects and rights to which a process has access, and those objects and rights change when a process moves from one LNS to another.
A protection domain in Hydra is the "local name space" (LNS): "At any instant, the execution environment (domain) of a program is defined by an LNS object associated with it...the rights lists in each capability define the permissible access rights of this program at this instant." (Hydra p. 341).