When I accept to supervise a thesis (be it a Bachelor, Master, or Doctoral Thesis), I will ask the candidate to produce, as the first milestone in the project, an exposé of his or her thesis. Its size and the time available for producing it differ for the three types of theses: For a Bachelor thesis, it should be available about 2-3 weeks after the formal thesis start; for a Master thesis after 1 month; for a Doctoral thesis after 3 months. However, the idea and structure are equal in all three cases.
A thesis is a one-person research project, and think of the exposé as a project plan. It needs to answer the questions: What is the goal of the project? Where does it start from? Why bother? What is the plan to run it in time? In terms of a research project and a thesis exposé, this leads, more sternly, to the sections:
Have you ever seen in a supermarket a bottle with the label saying “Bottle”? A can called “Can”? Yet, many students decide to call their theses exposé “Exposé”. That makes no sense – “Exposé” could be or appear in the subtitle, but the title should be the working(!) title of your planned thesis. Working title means it may well change in wording and/or detail while you are working on the subject for your thesis later until thesis submission, but it should reflect clearly the main goal and/or contribution of the planned thesis. Please don’t forget to put your name on the exposé as the author!
Describe the goal of your work. This may concern an analytical result (e.g., proving that P $\neq$ NP), or an empirical one (e.g., examine the performance of the HAYAI algorithm on gravel paths), or a constructive one (e.g., a new algorithm for stereo matching of images taken in complete darkness), or – most frequently for an Informatics thesis – a combination of the three (e.g., a new 3D scan matching algorithm running in O(log log n) and its evaluation in a botanical garden). Normally, the title of the thesis would reflect the goal.
Give a sketch of the state of the art that your thesis sets out to improve. In an exposé, the sketch has to be very short and to the point, mentioning exactly the top most relevant papers. For a university thesis, the background includes stating which local equipment and results you will use, if any (e.g., a robot running the HAYAI algorithm).
If you have absolutely no idea where to start in order to reach your goal, you will probably not make it in time for thesis submission. State here where you will start working. In many cases (typically in Bachelor theses, often in Master theses), a particular approach is enforced as part of the thesis topic that you get.
State briefly in what respect you expect your result to be significant. It should somehow improve on the state of the art, or provide new empirical data, or lead to a result that was never there before.
Break down your thesis project into smaller steps and make a schedule what you plan to do in which order and in what time. Plan in the order of weeks and months rather than days. If possible and useful, formulate milestones, i.e., important intermediate results. Plan the immediate future in more detail than the distant one. Don’t plan for doing all the technical work first, and writing everything down from scratch in the last three weeks: That will almost never work out! Plan to interleave the reading/thinking/programming/experimenting and the writing.
The author of the exposé is the candidate, i.e., you! Why?: Your thesis supervisors have normally an idea of the thesis topic that they give to you. Your formulation in the exposé shall make sure that you have the same understanding of what you are supposed to work on. Moreover, much of the exposé text may in fact go into your final thesis: a typical introduction shares much of the material with your exposé, and you should have written that yourself.
Be prepared, however, to adjust your topic while working on it! In fact, this is the norm rather than the exception, which leads to the final remark about the exposé: This is a plan for your thesis work, and, like all plans in life, is subject to revision in detail! Don’t hesitate to change details of what your exposé says, if it turns out to be necessary. However, do hesitate to change significantly the topic and approach of your thesis that you have described in your exposé – before you do that, consult your instructors!