Midterm Examination

CSci 555 / Neuman Fall 1992
Directions for completing exam

Answer the following three questions.

1. (35 points) You have been hired by Southern California Airlines to design their new distributed flight reservation system. Your first task is to decide how changes made at remote workstations will be communicated to other parts of the system. Describe the communication method you would use (e.g., messages passing, remote procedure call, shared memory, or work queue). Discuss the reasons for your choice, comparing it with the alternatives. Be sure to mention any negative implications of your choice.
2. (25 points) While the purpose of both transactions and virtual time (i.e. time-warp) are to maintain consistency in the face of concurrent execution, they solve two different problems and each is appropriate in different situations. Compare the specific function of each mechanism and describe a problem/situation for which each is appropriate.
3. (40 points) You have been hired by NASA to design a directory service to organize images and other data collected by their spacecraft. These images are stored at many different sites and it is expected that more sites will come online in the future (through cooperation between NASA and other agencies, and in the distant future perhaps even as data become available from other civilizations). Discuss possible approaches for cataloging this data. Note: this problem is underspecified, your discussion should discuss how different requirements affect your approach.

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