umr 5205 "methodology" of research in computer science lionel brunie national institute of...
TRANSCRIPT
UMR 5205
"Methodology"of
research in computer science
Lionel Brunie
National Institute of Applied Sciences (INSA)LIRIS Laboratory/DRIM Team – UMR CNRS 5205
Lyon, France
http://liris.cnrs.fr/lionel.brunie
Master Course, Lyon, January 2015 - Methodology of Research in CS
Agenda
(Disclaimer)
Discovery vs. invention
What is a research result in computer science?
What is a research paper in computer science?
General structure(s) of a research paper in CS
Searching for black boxes, traps and black holes
How is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS 3
Agenda
Disclaimer
Discovery vs. invention
What is a research result in computer science?
What is a research paper in computer science?
General structure(s) of a research paper in CS
Searching for black boxes, traps and black holes
How is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
Disclaimer
This is NOT a lecture !
I apologize not to be an epistemologist
I am just a practitioner of computer science that have co-
authored some research papers and read/evaluated several
hundreds ones
This open discussion is absolutely NOT objective
Goal : open the windows and discuss how we ACTUALLY
work (and not how we should work…)
All questions, remarks, contradictions are welcome!!!
Master Course, Lyon, January 2015 - Methodology of Research in CS
Agenda
Disclaimer
Discovery vs. inventionWhat is a research result in computer science?
What is a research paper in computer science ? General structure(s) of a research paper in CS
Searching for black boxes, traps and black holes
How is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
Discovery vs. Invention
My feeling is that there are two main ways of practicing science : discovery vs. invention
Biologists, physicists, chemists, researchers in psychology… are discoverers
(at least, software) Computer scientists, researchers in nanotech, researchers in process engineering or in industrial engineering… are inventors
However inventing often needs a priori discoveries (e.g., of your target/domain of interest); discovering often needs inventing (e.g., measuring instruments)
Mathematicians… are mathematicians :-)
Master Course, Lyon, January 2015 - Methodology of Research in CS
Discovering (just two words)
Understanding the world : what are atoms constituted of, why a disease in inherited, why do people have dreams, etc.
Understanding means first asking questions, then observing, inquiring, modeling, evaluating
At the end of the research process, one has an answer to the initial question (question of research)
An answer is the most often not definitive. It is an explanation of a small piece of the natural world under some hypotheses
Famous recent example: the “proof of the existence” of Higgs’ boson at CERN/LHC
Master Course, Lyon, January 2015 - Methodology of Research in CS
Inventing (1/2)
Software computer science produces inventions
Computers do not exist by themselves. They have been created by human beings => there is nothing to discover in a computer or in a software
The objective of research in CS is “just” to make computers/computer networks and computer applications more efficient, more easy to use, more reliable, more powerful… i.e. more useable/useful
Master Course, Lyon, January 2015 - Methodology of Research in CS
Inventing (2/2)
As a consequence, a research result in (software) CS has no (real) intrinsic value. It has only the value that the research community and/or the society gives to it. A useless invention has no value!
This has to be moderated when one considers research in fundamental and theoretical CS where people study formal problems => context actually close to research in maths
This has also to be moderated when one considers social- or bio- or something-inspired CS where researchers attempt to understand and model an “external” (social or biological or…) phenomenon
Master Course, Lyon, January 2015 - Methodology of Research in CS
Agenda
Disclaimer
Discovery vs. invention
What is a research result in computer
science?
What is a research paper in computer science? General
structure(s) of a research paper in CS
Searching for black boxes, traps and black holes
How is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
A difficult answer…
The endless debate about fundamental research, basic research, applied research, finalized research…
A first and definitive answer: a result has some scientific value as soon as it has been accepted by a scientific publication (a scientific committee), i.e., research is a social activity (hence, fashions, trends…)
A second answer: a result has some scientific value if it interests people and if it is novel (original) (and if it has some genericity) i.e., refer to the scientific method
The most difficult (and so the most interesting) problems have often been raised by applications, e.g. medical applications. Investigating these problems have allowed going through theoretical scientific developments
Master Course, Lyon, January 2015 - Methodology of Research in CS
Agenda
Disclaimer
Discovery vs. invention
What is a research result in computer science?
What is a research paper in computer science? General structure(s) of a research paper in CSSearching for black boxes, traps and black holes
How is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
Introduction-Motivations
State of the art
Proposal
Experiments
Discussion
Conclusion and future work
=> Computing the oror!
Structure of a research paper in CS
Master Course, Lyon, January 2015 - Methodology of Research in CS
3 (+1) key sections (1/4)
Having 1 very good idea in a scientist’s life is… very good; having two is exceptionalOne paper => one problem and at most one (two) contribution(s) to defend
A first key section: the statement of the problemWhy is the problem important? Remark: notion of fashion (e.g., Big
Data)Why is the problem difficult (→ link to the state of the art)?What are the hypotheses? What is/are the context/conditions?What are the objectives i.e., what are the performance/quality
criterions with respect to which the contribution should be evaluated?
Then, add the outline of the contribution
Master Course, Lyon, January 2015 - Methodology of Research in CS
3 (+1) key sections (2/4)A second key section: the state of the art
A state of the art must not be “flat” or general purpose
It must be focused on your scientific and applicative targets and “critical and compared/taxonomic”
Critical: the contribution/limitations of each cited paper should be analyzed wrt your problem
Compared: papers should be organized in taxonomies
The state of the art establishes/describes the scientific basis wrt which your work should be compared, i.e., your // will be evaluated
Ideally, all pertinent papers should be analyzed. Practically, it is often untracktable
“Making the bibliography” is a key component of the scientific method
Master Course, Lyon, January 2015 - Methodology of Research in CS
3 (+1) key sections (3/4)
A third key section: the discussionGoal of the discussion: analyzing your
contribution/proposalWrt to your initial objective/motivationWrt to the state of the artWrt the experiments you have run… and have not runWrt the implementation choices you have madeWrt genericity
A discussion is not a conclusion
The discussion is often distributed over the paper ( :-( ?)
Do not believe authors: make your personal discussion!
Master Course, Lyon, January 2015 - Methodology of Research in CS
3 (+1) key sections (4/4)
A fourth obvious section : your contributionMust be “sound”
Must be comprehensive and complete
Should allow people to reproduce the experiments you use
Must be self-contained
Master Course, Lyon, January 2015 - Methodology of Research in CS
A short focus on the“Introduction – Motivation” section
Inventing some “thing” that interests nobody has no real senseInventing some “thing” that addresses a problem that has an existing satisfactory solution has a limited interestTo be interesting, a work/paper should address a problem :
With a high (scientific or economic or social or…) valueAnd no solution
(already noted) A paper should list the criteria wrt which authors consider that their proposal is to be evaluated
Master Course, Lyon, January 2015 - Methodology of Research in CS
Experiments (1/3)
The often dark side of research in CS
A first reason : cultural/educational : computer scientists have an unsatisfactory education in statistics/experiment planning/performance evaluation
However, things become better :-)
Master Course, Lyon, January 2015 - Methodology of Research in CS
Experiments (2/3)
A second reason : real life experiments are often intractable because comparing two inventions is often intractable
Concurrent software are often not availableConcurrent complex systems/softwares cannot be re-
develop from scratch at a reasonable priceEvaluation criteria are differentUsers of your software are reluctant to spend/waste their
time on alpha versionsIt often exists no benchmarksResearch works often address very small range/specific
issues that are part of a complex systems but integration is often not realized
Research teams have neither the manpower nor the competence to develop “products” and limit their development to demonstrator or prototypes that cannot be tested by real end users
Master Course, Lyon, January 2015 - Methodology of Research in CS
Experiments (3/3)
However experiments are mandatory to evaluate the pertinence of your work
Experiments should allowTo evaluate the performance/pertinence/efficiency of your
proposal wrt your initial objective and wrt all the possible contexts (not only in the best case)
To evaluate the influence of the various parameters on the performance
To compare your proposal wrt the state of the art
Experimental conditions must be made completely explicit
Master Course, Lyon, January 2015 - Methodology of Research in CS
Agenda
Disclaimer
Discovery vs. invention
What is a research result in computer science?
What is a research paper in computer science? General structure(s) of a research paper in CS
Searching for black boxes, traps and black holesHow is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
Reading a paper as an investigation
A key behavior: criticism (cf. methodical doubt by Descartes)
A first obvious step : analyze what is written is the proposal scientifically sound?are the performances good?is the problem really important?is the state of the art exhaustive?etc.
A second step : analyze what is not written
Master Course, Lyon, January 2015 - Methodology of Research in CS
Black boxes and assumptions
Computer systems/applications/software are too complex/too large so that a single team/paper can address the entire problem
=> Focus on a small part or specific issue
=> Assumptions on the other parts
+ inputs: it exists/will exist (soon) some “system” can can provide your prototype with the data/information it needs
+ outputs: the data produced by your prototype could be/will (soon) be used by the end-user side of the global system
Assumptions are not always explicit
Always ask yourself if these assumptions are valid/realistic, what do they imply
Master Course, Lyon, January 2015 - Methodology of Research in CS
Analyzing experiments (1/3)
The border line“Science” definitely condemns treachery and falsification:
modifying the result of an experiment is beyond the “red line”Experimental measurements that are presented in a paper are
(supposed to be) true (I personally have always supposed it)The question is about omitted/”forgotten” resultsThe question is about uncertainty and statistical errors on the
measurementsThe question is about some generalization of
results/experimentsFrom a scientific point of view, a negative result is often as
interesting as a positive resultHowever, as CS has to deal with invention, a negative result is
usually considered as a depreciated fact
Master Course, Lyon, January 2015 - Methodology of Research in CS
Analyzing experiments (2/3)
So the temptation to “avoid” including negative measurements often exists:
“This measurement is not really important but as I do not have enough space to explain it, it is more important, from a scientific point of view (of course), to discuss in deep other more important experiments”
“The situation that leads to this bad result never happens in the real life”
“With a slight modification of the prototype, it is obvious that one would never get such a result, so let us focus on the results concerning the core of the prototype”
etc.
are reasons that a scientist may use to self-persuade him that presenting this experiment is not pertinent
Master Course, Lyon, January 2015 - Methodology of Research in CS
Analyzing experiments (3/3)
Where is the yellow line? Where is the red line?
Always analyze if experiments are exhaustive
If not, always analyze if the missing experiments are
important to evaluate the performance of the prototype
and try to infer what could be the behavior of the
prototype wrt these experiments
Master Course, Lyon, January 2015 - Methodology of Research in CS
Agenda
Disclaimer
Discovery vs. invention
What is a research result in computer science?
What is a research paper in computer science? General structure(s) of a research paper in CS
Searching for black boxes, traps and black holes
How is a research paper evaluated?And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
Evaluation of a research paper
Is the topic of the paper in the domain of interest of the conference/journal?
(Is the bibliography complete, critical and taxonomic?)
Is the contribution original?
Is the paper technically sound/correct?
Is the paper easy to read?
Is the contribution significant?
What is the level of expertise of the evaluator / what is the confidence of the evaluator in his judgement
Discussion within the program or scientific committee
Master Course, Lyon, January 2015 - Methodology of Research in CS
Menu
Disclaimer
Discovery vs. invention
What is a research result in computer science?
What is a research paper in computer science? General structure(s) of a research paper in CS
Searching for black boxes, traps and black holes
How is research evaluated?
And now?
Master Course, Lyon, January 2015 - Methodology of Research in CS
Conclusion?
Read, read, read, read!
Be positively critical
Never admit supposed evidences. Always doubt (Descartes)
All questions are good
Be modest