UNIVERSITY OF MANCHESTER
SCHOOL OF COMPUTER SCIENCE
Fundamentals of Distributed Systems
Date: Monday 6th June 2016
Time: 14:00 - 15:30
Please answer any TWO Questions from the THREE Questions provided.
Use a SEPARATE answerbook for each QUESTION.
This is a CLOSED book examination
The use of electronic calculators is permitted provided they
are not programmable and do not store text
[PTO]
, COMP18112
1. a) Imagine you are a software engineer in Goodlet, a web-based company whose main
business process relies on aggregating adverts of properties for sale. These adverts
come from a large number of estate agents. Goodlet makes money by charging each
estate agent a fee every time that a Goodlet website user converts into a prospective
customer (say, by requesting further details on a property, or by requesting to visit
a property, etc.).
i) Jack, a colleague of yours, has argued that, from the viewpoint of the estate
agents, the main reason for them to participate in the distributed system created
by Goodlet, is non-functional. State whether or not you agree with Jack and
briefly explain why.
(3 marks)
ii) Jill is another colleague of yours. She has argued that Goodlet should expand
its business processes by developing a RESTful API. This would allow Goodlet
to charge third-party applications (say, interior decoration companies, etc.) for
access to the estate agent data they hold. Goodlet would then pay the estate
agents a share of the revenue that had been generated in this way. Explain why
this new initiative would characterize, from the viewpoint of the estate agents,
a functional reason to participate in the distributed system created by Goodlet.
(3 marks)
iii) Assume that Goodlet adopted Jill’s proposal (in 1(a)ii above) for exposing a
RESTful API for third-party applications to access their data. Argue that, in
this extended Goodlet system, all the components have the features required in
the definition of distributed system discussed in this course unit. (5 marks)
b) In this course unit, we placed five computation models in a spectrum, from [1] the
basic centralized model to [5] those distributed systems that rely on middleware.
Choose two of the remaining models and explain what their distinctive features
are. (3 marks)
c) Multi-CPU systems are a kind of of modern chip multiprocessor (CMP) in which
processing units that are physically separate rely on a separate interconnect (in
other words, a bus) to communicate. For each one of the eight axioms of distributed
computing discussed in this course unit, briefly explain whether that axiom applies
or not to a multi-CPU CMP. (In your answer, you must take the bus that connects
the multiple CPUs to be what in the axioms is referred to as “the network”.)
(8 marks)
d) An operating system (OS) uses priority-based preemptive scheduling. This means
that an OS takes into account the priority of a job before it suspends the execution
of that job in order to allow another process its share of CPU time. Given the above,
briefly explain why graphical user interfaces (GUIs) are likely to be treated as high
priority by OS schedulers. (3 marks)
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