Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

How to Prepare a Seminar Talk

This document contains rules and guidelines for students that plan to participate in a seminar offered by members of CADMO. The goal of these is to make the seminar a pleasing experience for all participants.

Please read this document carefully before starting to prepare your talk. There are a few formal requirements at the beginning; please make sure that you understand them, in order to avoid later surprises.


Admission (this paragraph is relevant for the Seminar of Theoretical Computer Science (Mittagsseminar) only). This is a joint research seminar of several theory groups. Speakers as well as the audience mostly consist of professors, postdocs, and doctoral students. We welcome master students who want to take this seminar for credit and satisfy the formal admission criteria as published in the course catalog; however, participation is only recommended to students with excellent performance. Please take this very seriously: this is a seminar in which the audience expects to learn from your talk. Some listeners may already know something about the topic and ask in-depth questions about aspects of it. Others who are not familiar with the topic will ask questions if explanations are not sufficiently clear. Excellent students may view this seminar as a challenge (it is intended as such from our side), but failure to answer the questions of the audience appropriately can also result in unfortunate outcomes, including a failing grade for the presentation. Additional rules apply as outlined on this page.

Language and duration of the talk. Your talk is expected to be in English by default (but German is an option also in the Mittagsseminar). The talk should be 45 minutes long, and this is a hard limit. A presentation of a Master / Bachelor thesis should only last 30 minutes.

Attendance. You must attend all talks of the seminar. If your are absent for some important reason, please provide according documents.

Preparation. There will typically be at most two meetings with your advisor. During the first one you can clarify any questions you may have on the content and discuss principle ideas of how to structure your talk; at the second meeting you can clarify additional questions that may have arisen during the preparation of the talk; alternatively you may want to hold your (polished) talk in front of your advisor to get feedback and ideas on how to improve the talk even more. The two meetings with your advisor should be separated by roughly a week, and the second one should take place roughly a week before the rehearsal talk (see next item). So please start early enough with preparing your talk!

Rehearsal talk. At least one week before your seminar talk, you need to give a rehearsal talk in front of your advisor. The benefit of this rehearsal talk is mutual. You convince your advisor that you will be able to give a reasonable seminar talk; in return, your advisor will give you feedback that helps you to further improve the presentation.

If the rehearsal talk fails to meet minimum quality requirements, a second rehearsal talk will be scheduled, attended by your advisor and a senior member of the advising group. The need for a second rehearsal talk will have a negative impact on your final grade. If also the second talk talk is not satisfatory, your actual seminar talk will be cancelled. This has the consequence that you will not be able to successfully participate in this seminar anymore, and you will obtain a failing grade.

In order to meet the minimum requirements, your rehearsal talk must be complete. It must contain all the material that you also plan to present in the seminar talk, and at the same level of detail. It is not an option to show up for the rehearsal talk with missing pictures, or with details not yet worked out. Also, the rehearsal talk must be understandable to your advisor. There may be some deficiencies that you can still take care of based on the feedback that you get, but the talk must have a clear potential of being brought into an acceptable state within the remaining time.

Choice of material, and goals of the seminar

In the beginning of the seminar, you will decide on one among a number of research papers that are being on offer for the seminar, and with this you will get an advisor to guide you through the preparation of the talk. It is important to understand that the paper is an entry point for your preparation. You will not necessarily have to present all material from this paper, and the talk may also use other sources: literature cited in the paper, websites, demos, etc. In this sense, the talk is not so much about the paper itself, but about the topic addressed in the paper.

It is important that you get yourself informed about the current state of research on the topic. Some more recent results may not be covered by the paper that you are reading. For hot topics, it may even happen that new results come out while you are preparing your talk. You are not expected to present such new developments in detail, but you are expected to know about them and be able to answer questions concerning the topic's state of research.

The seminar has two goals. On the one hand, you should learn to put together an interesting presentation. This means that you must do some research: get an overview about the topic at hand; what is it all about, and why is it interesting? What is the background, and what have other people already done? Then you should develop an idea of what to present. Your advisor will be of help, but your own initiative is important. For example, you might discover that another paper about the topic is a much better source for material that fits your idea.

The second goal is that the audience learns something worthwhile, and you should seriously think about what you want this to be. It can be very painful to endure talks that have not been prepared with this goal in mind, and a bad or even failing grade is a foreseeable consequence.

Preparation, and the talk itself

Usually you have a couple of weeks for preparation during which you are invited to contact your advisor. Here are the main guidelines.

Use electronic slides! It doesn't matter whether it is Powerpoint, Keynote, Slitex, Beamer, or still other systems. These days, the only serious alternative to electronic slides are pure blackboard talks, but giving good blackboard talks is something for the experts. Well-prepared slides guide you through your talk almost automatically. It is usually a good idea to change media and go to the blackboard once or twice during your talk to present a crucial proof or draw an important figure. This tells the audience that something special is going on now.
Hint: Please avoid using green colors on white background, as these are either invisible or hurting the eye on most beamers.

Show many pictures! Yes, drawing good pictures takes a lot of time, but it is an absolute must. It is very difficult for the audience to understand even simple definitions without an illustration. You have prepared this for weeks and (hopefully) know it by heart, but the other people hear it for the first time. Pictures add redundancy, so they allow the audience to cross-check whether their understanding of the previous formal definition was correct. Explaining pictures also slows down the presentation and gives people the time necessary to absorb the material.

Use large font, and show one thing at a time! Overfull slides in small font are a nightmare. A slide only helps if it corresponds to what the speaker is telling at the very moment. Slides that stay on for minutes while the speaker is simply droning on makes the audience lose attention. There may be technical slides (that explain an algorithm, say) which are necessarily somewhat denser, but these should be exceptions. Every slide should focus on just one issue.

Be clear and mathematically correct! If you present an algorithm that solves a certain problem, you should make sure that you properly define the problem in the first place. When you use some fact without proving it (which is perfectly ok), you should say whether this fact is (a) easy to see, (b) requires a simple proof, or (c) requires an involved proof. Mathematical definitions and theorems should be stated completely and correctly. If you do not follow this guideline, two things happen: some people just lose attention, since they didn't fully understand the problem, got confused by unclear things that you said, or still try to figure out whether that fact you just used is obvious or not. Other people (the ones that grade you, mainly) will ask you to clarify things. In general, questions during the talk can be very inspiring and lead to interesting discussions, but if it takes five minutes of discussion just to get an unclear definition right, this causes unnecessary delays.

The essential rule here is: keep it simple, but do the simple things well. There is only so much you can say in 45 minutes, so it makes sense to prefer simple over complicated material. Our offered selection of topics supports this approach.

Understand what you present! This may seem self-evident, but let us do a concrete example that makes the point. You mention (and/or write on the slide) that the existence of this and that object follows from a standard result in analysis. Now somebody asks whether you can say what this standard result is. If you don't understand what you present, you now say something like "I don't really know, this is just what they wrote in the paper". The resulting impression on the audience is very bad. If you do understand what you present, you know it/have looked it up/asked your advisor so that you can say "The standard result is that every continuous function attains a minimum over a compact set". As a general rule, you must be able to explain everything that appears on any of your slides. If you can't, don't write it. The fact that the paper does not explain it is no excuse; scientific papers often omit details, and it is part of your preparation to fill them in if necessary.

Understanding what you present is also the key to being more confident and less nervous. It is normal to be nervous, but this is hugely amplified if you don't have full understanding of your presentation.

Prepare for delays! Despite the best preparation, you may run out of time, and this is not a problem per se. After all, the audience is not fully predictable, and your presentation speed isn't, either. But you must prepare for such a case. It is not an option to stop in the middle of an important proof, or to simply go overtime and wait for somebody else to stop you. The best way is to have some material in your talk (preferably close to the end) that you could skip if necessary, without compromising the talk on the whole. For example, this could be an additional result that is not necessary for understanding the big picture that you present.

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