04/02/2021 1


DEPARTMENT OF COMPUTER SCIENCE AND TECHNOLOGY
COURSEWORK ASSESSMENT DESCRIPTION 2020/21

MODULE DETAILS:
Module Number:

600094
Trimester:
2
Module Title:

Advanced Software Engineering
Lecturer:

Professor Yiannis Papadopoulos
COURSEWORK DETAILS:
Assessment Number: 1 Of 1
Title of Assessment:

Reliability and Safety of Systems
Format:

Report 2nd format 3rd format
Method of Working:

Individual
Workload Guidance:
Typically, you should
expect to spend between
16 And

24

hours on this
assessment
Length of
Submission:
This assessment should be no
more than:
(over length submissions will be
penalised as per University policy)
1000 words
(excluding diagrams, appendices,
references, code)
PUBLICATION:
Date of issue:

15/02/2020
SUBMISSION:
ONE copy of this
assessment should
be handed in via:
Canvas
If Other
(state method)

Time and date for
submission:
Time 2pm Date 16/04/2020
If multiple hand–ins
please provide
details:



Will submission be
scanned via
TurnitinUK?
No
If submission is to be scanned byTurnitin, these should
be one of the allowed types e.g. Word, RT, PDF, PPT,
XLS etc.
Specify any particular requirements in the subumission
details
Students MUST NOT submit ZIP or other archive
formats unless specified.
Students are reminded they can ONLY submit ONE file
and must ensure they upload the correct file.
Normally only the LAST submission will be considered
(and if late incur a late penalty).

The assessment must be submitted no later than the time and date shown above, unless an
extension has been authorised on a Coursework Extension Form: see the Canvas site:
Help&Support > Student Forms


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MARKING:
Marking will be by:

Student Number

ASSESSMENT:
The assessment is
marked out of:

100
and is
worth
50
% of the
module
marks
N.B If multiple hand-ins please indicate the marks and % apportioned to each stage above (i.e.
Stage 1 – 50, Stage 2 – 50). It is these marks that will be presented to the exam board.

ASSESSMENT STRATEGY AND LEARNING OUTCOMES:
The overall assessment strategy is designed to evaluate the student’s achievement of the module
learning outcomes, and is subdivided as follows:

LO Learning Outcome Method of Assessment
{e.g. report, demo}
1





2





Intellectual Skills: Explain, with comprehension, a
range of issues which are pertinent to the
reliability of computer systems and their
relevance to the causes and mechanisms of
failure.

Intellectual Skills: Explain, with comprehension,
a range of issues which are pertinent to the
application of techniques in the off-line analysis
and on-line detection and containment of
hazardous failures.


Problem solving exercises
Q1,Q2 in report






Problem solving exercises
Q1,Q2 in report


Assessment Criteria Contributes to
Learning Outcome
Mark

Q1
Q2

1,2
1,2
50
50

FEEDBACK
Feedback will be
given via:
Annotation
Feedback will
be given via:
N/A
Exemption
(staff to explain
why)

Feedback will be provided no later than 4 ‘teaching weeks’ after the submission date.


This assessment is set in the context of the learning outcomes for the module and does not by
itself constitute a definitive specification of the assessment. If you are in any doubt as to the
relationship between what you have been asked to do and the module content you should take this
matter up with the member of staff who set the assessment as soon as possible.

You are advised to read the NOTES regarding late penalties, over-length assignments, unfair
means and quality assurance in your student handbook, which is available on Canvas.

In particular, please be aware that:
• Up to and including 24 hours after the deadline, a penalty of 10%
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• More than 24 hours and up to and including 7 days after the deadline; either a penalty of
10% or the mark awarded is reduced to the pass mark, whichever results in the lower
mark
• More than 7 days after the deadline, a mark of zero is awarded.

• The overlength penalty applies to your written report (which includes bullet points, and lists
of text. It does not include contents page, graphs, data tables and appendices). 10-20%
over the word count incurs a penalty of 10%. Your mark will be awarded zero if you exceed
the word count by more than 20%.

Please be reminded that you are responsible for reading the University Code of Practice on
Academic Misconduct through the Assessment section of the Quality Handbook (via the
SharePoint site). This govern all forms of illegitimate academic conduct which may be described
as cheating, including plagiarism. The term ‘academic misconduct’ is used in the regulations to
indicate that a very wide range of behaviour is punishable.

In case of any subsequent dispute, query, or appeal regarding your coursework, you are reminded
that it is your responsibility to produce the assignment in question.



Description of assessment task.


04/02/2021 4
Reliability and Safety of Systems

ACW on Advanced Software Engineering
(Submit your report via Canvas by 2:00 pm on Friday 27/03/2019)

Yiannis Papadopoulos


Answer questions Q1 and Q2:
Q1. In the following fragment of code, k and y are integer variables as declared.

int k,y;
...
y=y-4*k-18;
while (k>3) {
k--;
y=y+4;
}
i) If k1 and y1 are the values of k and y just before the execution of the while statement, what
conditions must k1 and y1 satisfy to cause the unsafe condition “y<0” after the while statement?
Both cases of (k>3) being true and false must be examined.
Explain how you have derived these conditions. [20 marks]

ii) If ko and yo are the initial values of k and y just before the execution of the first assignment (i.e.
y=y-4*k-18), what conditions must k0 and y0 satisfy to cause the unsafe condition “y<0” after
the while statement? Both cases of (k>3) being true and false must be examined.
Explain how you have derived these conditions. [10 marks]

iii) Using the results of the analyses and calculations that you have performed in i) and ii) above,
draw a software fault tree to show how the unsafe condition “y<0” can arise from the execution of
this fragment of code.
For simplicity, assume that operand evaluation is always reliable and that no exceptions can
occur during the execution of the above code.
[20 marks]



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Q2. The system illustrated below transfers fuel to the Engine when at least one valve is open and one
pump operates.


Assuming that in this system the possible basic faults are:

VA: Valve A stuck closed
VB: Valve B stuck closed
PA: Pump A broken
PB: Pump B broken
CP: Controller inadvertently stops both Pumps A and B
CV: Controller inadvertently closes both Valves A and B
NI: No input flow

(i) Draw a fault tree to show how the event of “No flow to the Engine (NFE)” arises from
combinations of those basic faults. Use standard rules of fault tree construction. Use the
short names in capital letters to refer to basic faults in the fault tree.
[20 marks]

(ii) Calculate the minimal combinations of basic faults (i.e. minimal cut sets of fault tree) that
cause NFE.
[15 marks]

(iii) Identify single points of failure in this system.
[5 marks]

(iv) Assume that there are no failure detection and control measures in this system. Give
examples of two measures that could be incorporated in the monitoring and control software
of the Controller to improve the design of this system.
[10 marks]





V alve A
Pump A
E ngine
C ontroller
Valve B
Input
Flow


Pump B













































































































































































































































































































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