PhD Thesis Structure and Content

A [perfect] PhD Thesis for London University / Computer Science UCL.

These notes of preparing the [perfect] PhD thesis structure and content stem from an ISRG lunch-time meeting at UCL CS. Chris Clack initiated the meeting, with contributions from the floor - staff OR students. Made available for information only, with no London University sanction.

A Thesis is:

A thesis is the acquisition and dissemination of new knowledge.

In order to demonstrate this the author must demonstrate that they understand what the relevant state of the art is and what the strengths and weaknesses of the SoA are. For someone's work to be knowledge there must be a demonstration that suitable and systematic methods were used to evaluate the chosen hypothesis.

It is important that "new" is not just new to the researcher, but also new to the community - PhDs were sometimes in the past failed because a paper was published by another researcher a few weeks previously dealing with the same work. I don't believe this is as common today, but novelty/originality/new understanding/marshalling existing ideas in ways that provide new insights is what it is all about.

A PhD Thesis Must Contain:

Knowledge, understanding, and appreciation of the field
This will show motivation, relevance to X, Y, & X, who is doing what, &c.
Critical analysis of related work.
Person X is doing Y, this is important because ..., this doesn't address these points ... Link the failings of related work to your own work.
Importance (relevance) of own work.
State contributions, is this an incremental improvement on the state of the art, an evolution on existing work, &c. Beware of appearing to be too original, don't appear to have missed or ignored existing work.

A PhD Thesis is Not:

Not "a diary of work done".
In order to be awarded a PhD you must be able to present your work so that it is accessible to others and so that it demonstrates your mastery of a given subject. Although PhD theses may differ widely, you certainly won't be awarded a PhD just for doing three year's work and you won't be awarded a PhD for "a diary of work done".

A common attitude is "well, I've done my PhD, now all I've got to do is write it up". Beware! The thesis IS the PhD - it doesn't really matter how great your research has been during the three years - all that really matters is the thesis.

Not "a collection of papers".
At UCL this is not an acceptable PhD thesis (some other universities allow this as a PhD route, e.g. for staff, but the required standard is very high). At UCL your thesis must have a THEME. It is similar to writing a book. You can however take a collection of papers and turn it into the core of a PhD.
Not "a big 3rd year project".
Though some 3rdyr projects are excellent, most do not contain sufficient critical analysis or scientific method.
Not "a lone journey".
It is important to have other people involved, if for nothing else then for proof-reading. You need to have an experienced supervisor who can tell you when to stop! (this is often the biggest problem faced by students). As the person doing the PhD, you are too involved and therefore you have the worst judgement on what is good or bad - you must get external advice. Also remember that a thesis should be designed for the benefit of the reader, not the writer! So get lots of people to read your thesis and tell you what parts they could not understand.

Typical PhD Thesis Layout

Note: Should have an odd number of chapters, between 5 and 9.
1. Introduction
Set the scene and problem statement. Introduce structure of thesis, state contributions (3-5).
2. Background
Demonstrate wider appreciation (context). Provide motivation. The problem statement and the motivation state how you want the PhD to be judged - as engineering, scientific method, theory, philosophy, &c.
3. Related Work
Survey and critical assessment. Relation to own work.

4-6. Analysis, design, implementation and interpretation of results
7. Critical assessment of own work
State hypothesis, and demonstrate precision, thoroughness, contribution, and comparison with closest rival.

8. Further Work
9. Summary Conclusions
Restate contribution



A PhD made up on only critical assessment may be possible (for UCL) but is extremely difficult.

Average, good, size for a thesis is 150 pages all in. Perhaps up to 50 extra pages for a big appendix and bibliography. Beware of the trend to write long and boring doctorates (papers, &c), improve your communications skills.

Another important datapoint: 2-3 conference, or 1-2 journal papers in respectable (ACM, IEEE, IOP like) places are good enough for chapters 4,5,6, and therefore the core of a PhD - testing by publication is a VERY good defense (or defence). Also note that the feedback from reviewers is extremely helpful, so all PhD students should be trying to publish their work (the feedback is even more useful when your submissions don't get published!).

Always think - Presentation. Be precise in all things, esp: the statement of the problem, the solution, methods and frameworks. Thoroughness == scientific method. You must show proof that your contributions are valid.

Chapter headings - use 7 or 9! An odd number of (total) chapters gives a balanced appearance to the work (CC has a reference to back this up).

8/1/1997, JF. Keywords: PhD, outline, structure

People's comments

(These will be summarised as soon as I have time)

Chris Clack

There is a book that I found useful in that it analyses different 
styles of rhetoric and presentation:

Designs In Prose
Walter Nash
Published by Longman, 1980
ISBN 0-582-29101-1

When he wrote this book, Walter Nash was a senior lecturer in English
at the University of Nottingham.  He explores both the patterns of
prose, from the large-scale design of completed text to the specific
structures of component phrases and sentences, and the psychological
and technical problems the writer encounters in prose composition.

I found it an entertaining book.

Jon Crowcroft

some stuff on 
i) progress
ii) content
would be neat....


year 1 should finish with 1, 2 and 3 (of your contents) pretty much
done and the headings for the rest filled in
year 2 consists of 4 and half of 5+6
year 2.5 is finishing this and year 2.5-end is 7,8,9

computer science is not a "Natural Science"
we construct systems, which we then examine by some means.....
so it is a "Virtual Science"

the number of possible worlds we can build in computing makes
this feasible. this also makes PhDs somewhat odd compared with Natural
Science or Engineering....where research tends to explore natural
systems' behviour (or even artificial systems, but relatively simple
ones made out of natural components)

we tend to use abstract tools, usually - analysis, simulation,
etc....although sometimes we "do classical research" through
measurements.....but first, we build our virtual system, and then have
to build a virtual  measurement toolkit, and then use it.....

we also use autmoatic systems to allow us to analyze the results
sometimes, so we can cope with exploring the large design space of a
virtual system in a phd lifetime - physcists, chemists and engineers 
(e.g. cosmologists, genetics, aerospace are learning the value of our approach)
there is a downside, in that often, a PhD takes a year to get to 
see what is worth building - this is why it is often wirth doing a PhD
in a larger research project context (just as physicists go and use
the accelerator at CERN.....:-)

 >It would be nice if we could turn these rough notes into
 >a good collection of advice, so if you've got any contributions
 >(questions students would like answered or advice from staff
 >who have examined PhDs) then please email me and I'll add them to
 >the Web page.
a PhD is "training" for research - i.e. you have to say to the
1/ here is some valid research
2/ here is the fact that i have learned how to do some research
to a large extent, chapters 1,2,3, and 7 do this....

Steve Wilbur

I have read the material you put on the Web - although its possible it has 
changed since I printed it out.  I agree with most of it, but I have a few 
suggestions which I think are important or might help.

(1. and 2. incorporated above)

3. A thesis must contain material on where the work needs to go from here.  
This is partly a critical assessment of how confident you are of the 
validity of the results, eg. typically a PhD does small-scale evaluation and 
a larger-scale one will be needed.  In some cases further ideas in related 
areas have come out of the work and should be flagged.  (For new PhD 
students browsing the further work sections of recent theses can be very 
useful in identifying interesting areas of study.)

4. In many cases experimental design is tricky and should be explicitly 
covered because it involves trade-offs and judgements by the researcher.

5. I do not think number of chapters is important.  I care much more about 
the content and structure (story).  However, I do feel strongly about the 
length.  Over about 100 pages of the body of the thesis I seem to note the 
strength of the work is inversely proportional to the length.  (Pascal: "I 
would have written a shorter letter but I didn't have the time".)  The 
important point is what you are saying, not putting a very large number of 
words on paper.  I find 120 pages at usual university layout standards about 
the limit for good to best theses.

6. I often find that the first 20-30 pages are a strong indicator of the 
strength of the candidate.  If they understand the context and they analyse 
the SoA well, the following work will usually be strongly focussed and well 
executed.  (However, a few people are very good analysts but not so good at 
developing their own ideas and evaluating them.)

Finally, Jorge says we should check out the following Web page for Advice on Reseach and Writing.