Institute for Informatics
Georg-August-Universität Göttingen

Databases and Information Systems

Uni Göttingen
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Institute for Informatics
Göttingen University
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Databases and Information Systems: Virtual Teaching

General Statement

  • In the Summer Term 2020 and Winter Term 2020/21, teaching will be mostly virtual. This is no problem for DBIS. All courses will at least virtually take place. The recent semesters showed that a relatively large number of students who successfully passed the exam at the end did not usually attend the lectures. The materials (slides, exercises) are online, there are Web services to experiment with SQL, XML, and RDF/OWL, and all required software is publicly available.
  • Lecture Recordings: The teaching persons are also in home office. We don't have something like a SmartBoard (even no SmartScreens). A "live lecture" is a dynamic thing, including all kinds of flaws during live teaching.
    In contrast, the production of true tutorial-style "perfect" learning material requires a lot of time and resources (good cameras, excellent preparation, cutting the results etc.). We (especially the small groups who do most of the teaching) do not have these resources. On the other hand, there are some high-quality tutorials on databases and other areas available on the Web. We should not produce additional, mediocre ones.
    For the "Introduction to Databases" lecture there is an old recording that has been done when the lecture was transmitted to Clausthal. Since the material on relational databases does not change much, it can still be used.

BigBlueButton/GreenLight and RocketChat

  • Materials: as before, all information and materials is provided on the DBIS Teaching Web pages for each of the lectures.
    StudIP will be used to send mails to all registered participants of a lecture. Usually, we do NOT follow the forums in StudIP - for questions use mail or the RocketChat "dbis" channel instead.
    UniVZ will not be maintained except the general course data.
  • Main tool: We try use BigBlueButton provided by GWDG. There are (at least) two ways to login:
    • via StudIP (usually for teaching): Go to the StudIP lecture page, click on "Meetings", then click on the meeting's name.
      We usually create a new "Meeting" instance for each day of the lecture (otherwise StudIP would just show a sequence of camera symbols for the recordings of different days)
      Note that it takes some time until the recordings are available in BBB/StudIP. Note that in case there are several recordings made at/for a meeting (there might be a pre-prepared recording, a meeting-recording, and a post-prepared recording), they are shown in reverse order in StudIP, the leftmost one is the newest. There can also be meetings without any recording.
    • via Greenlight ("BBB directly"): In these cases, you need an explicit invitation (e.g. to our "DBISOffice" room for discussion of BSc/MSc theses).
      Students can also create own rooms, e.g. for group work and share them with others.
    • Note: these two "parallel worlds" do not see each other. In one's "Greenlight Home Room", one cannot see the lecture rooms.
    Browser issues:
    • For non-presenting participants: do not use the Safari browser. It has several problems with receiving shared screens. According to GWDG doc, also recordings cannot be viewed with it.
    • For presenting participants (incl. participants in lab courses etc. who do sub-presentations): Do not use the Safari browser. Firefox is problematic as the others will not see your mouse (but it will be recorded, but slightly misplaced).
      Chrome seems to be best for presenters.
    • If you have children/babyphone/dogs at home: users can mute their microphone with the symbol in the lower middle. Usually, passive participants best mute their microphone completely.
    Issues with large numbers of participants:
    • Video/cameras [as of summer term 2020]:
      • All video streams are generated at the sender, and not duplicated at the server. If 20 participants are active, each computer with active camera has to generate 20 streams. And each user's computer has to decode 20 streams. Up to 20 active cameras are possible.
    • Audio/microphones [state of the art discussed in RC 3.11.2020]:
      • Audio streams are duplicated and mixed on the server.
      • For every user that is shown in the participants list with a (green=active or red=muted) microphone, an separate audio stream is mixed without his microphone.
      • All other users (shown in the participants list with headphones = "listen only"), get the same stream (the union of all microphones)
      • Up to 80 active+muted microphones cameras are possible.
      • For lectures with more than 80 participants:
        • Allow/disallow "Share Microphone for non-moderators" can be set from outside (StudIP: creating the room or use the cogwheel symbol) and from inside (BBB: Users->cogwheel->lock viewers): In case of conflicts the inner setting dominates (or the last changed? - not important, see below)
        • Configure room initially to disallow microphones.
          Then, all user enter as "listen only", are shown with headphone symbol.
          This can be left as it is if they should never speak/ask.
        • Allow individual users later to speak and to ask is possible:
          Change from inside (BBB: Users->cogwheel->lock viewers->allow share microphones):
          All users stay with "listen only", are shown with headphone symbol.
          A single user who wants to speak can get an individual microphone as follows:
          1. click on the blue "phone symbol"->leave audio.
          2. then click on the white "phone symbol"->start audio->with microphone.
          Then, this user can speak, and all others still have "listen only" headphone symbol, and the new speaker is correctly added to all audio streams.
          Note: when muting his/her microphone again, it is still a -muted- microphone, so this can be done by about 80 users until problems arise.
          Note: resetting (BBB: Users->cogwheel->lock viewers->disallow share microphones) does not remove these (or at least the muted) microphones back to "listen only" with a common audio stream, but only prevents further users from also changing to microphone.
    Questions by participants during the session:
    • do not use "user->set status->raise", because the presenter will probably not see it (hardly visible; not visible at all if the presenter uses pdf or screen-share fullscreen).
      Note that during the lectures, we prefer to use the RocketChat channel (see below for details) for questions during the lectures (it is not recorded, and it rings on messages).
      The "public chat" of BBB can also be used (especially at the end of the lecture, when recording ist turned off), and might be seen if the presenter has set ": -> Settings->Audio+Popup Alerts for Chat"; he/she will probably hear/see it, and react in a suitable moment. But, this will be recorded.
  • As a secondary communication and fallback (in case BBB breaks down), there is a public channel at GWDGs RocketChat where offline questions can be answered, and where we will then be able at least to communicate how to go on and say goodbye.
    • avoid to use the direct message functionality - its answering functionality is buggy (answers are sent 9-11 times the same post/mail). Use mail instead.
  • Recordings: Usually, the lecture is recorded (if I don't forget to turn on and off).
    The general plan is to turn recording off when questions by users are stated, and then to turn recording on again when answering them if this makes sense, or afterwards (not only because of Datenschutz/Privacy, but also to keep the recordings short). So, in general only the lecturer will be recorded. The safest way if you want to be sure not to be recorded, is simply to be quiet (I guess that users cannot see whether recording is on (maybe forgotten to turn off)).
    As stated above, questions can be submitted via BBBs public chat (but usually, I have the presentation in full screen, so I may not see this; furthermore, the recording will in this case also record the name of the asking person).
    If you do not want this, we also use the separate public RocketChat "dbis" chat.
    • In the "Intro to Databases" BSc lecture, team members can answer questions during the lecture there (they can then also notify me about problems).
    • In the smaller lectures, posting there "rings" on my laptop, so I can react.
  • A really dirty spreadsheet about using BBB&RC.
  • NOTE: the lecturers are also doing home office. Sometimes, the teaching person may "disappear", e.g. when falling out of the home WLAN (can be back in some seconds). In one test session, when sharing the screen, my computer froze and had to be restarted completely (this took some time). In all cases, the teaching person will try to get back as soon as possible ...
    At least in the first weeks, there will be a DBIS member (passively) in the RocketChat "dbis" channel during the lectures, send a message there to "wake him up".

Communication Channels: DBIS Web pages, StudIP, RocketChat:dbis

Official information for the courses will ALWAYS be published on the DBIS lectures' Web pages ("blue pages"), SOMETIMES via StudIP (for quick "push" communication of announcements); usually, we do NOT follow the forums or "Blubber" chats in StudIP - for questions use mail or RocketChat "dbis" instead.
The RocketChat channel serves mainly as fallback and questions during the lectures, and might also be used for questions and help at any time. Note that UniVZ is not kept up-to-date for individual meetings etc. It serves for the general information about the course before the semester starts.


ShareLaTeX is also hosted by the GWDG.

  • Everybody can create documents and share with others. The basic screen presents the source code on the left, and the pdf on the right. Clicking on the vertical bar/border left of the line numbers, one can enlarge the source+result, by making the document list on the left smaller.
  • For exams, we will create the document and share it with the candidate before.
  • If several authors are active, in the upper right middle, symbols (e.g., a white-on-orange "W" if I am active) for them occurs.
  • One sees the own cursor (in black) and the cursor(s) of the other authors in the colors of their above.mentiones symbols. Clicking on the symbol brings you to the line where the other person's cursor is located.
  • sharelatex is pdflatex-based. So, it does not support pstricks.
  • With the green "Recompile" button, the small arrow on the right is a pull-down menu where you can set "auto-recompile on". It is quite error-tolerant (during editing there will be errors, and the result shown then might result from erroneous error-correcting strategies of the LaTeX compiler, e.g. when a math environment is opened, but not yet closed)
  • With ctrl-s (or strg-s on german keyboards) or clicking the green "Recompile" button, you can save and recompile manually.
  • copying and pasting in the source code (e.g. the helpful math symbols provided in the pattern) is done by ctrl-c and ctrl-v as in Windows.
    By this, you can also copy from the LaTeX source e.g. to copy SQL source code fragments from the sheet into a window where one of our Web services is open.
    copt to (X)emacs: mouse-middle will not paste. Click Edit->Paste.


  • Nobody knows how to do exams in the current situation. The main problem with online exams is the authentification of the candidate, and to guarantee that he/she does not get input from another person or via teleprompter (like some politicians when giving "free" TV speeches).
  • For oral exams of personally known persons (which I consider to be a sufficient authentification) in the advanced lectures (i.e., remaining Semantic Web exams from Winter Term 19/20) we will try to use BigBlueButton together with ShareLaTeX. A LaTeX source file like sharelatexexam.tex serves as a sheet where both the candidate and the examiner can write on, including formulas. We will prepare the sheet and share with the candidate before the exam (You should have some experience with LaTeX). Sharelatex then runs in the browser, but outside BBB, so BBB can be used in parallel with screen sharing:
  • Our SQL/XQuery+XSLT/RDF+SPARQL+OWL Web services can be used in screen sharing (the examined person should then use a browser that makes the mouse visible, like google chrome [not firefox, others not yet tested]).
  • So you should have the Web service corresponding to the exam topic in another tab or separate window. (then, use screen sharing with the whole screen or with the browser window or tab).
    Recall that the sharelatex is not to be shared via BBB because it is already shared with sharelatex. The examiner has also sharelatex in one tab, and BBB in another (or during screen sharing, in full-screen view).
  • We consider also to ask candidates to pre-prepare materials as a base for the discussion in the exam (similar to the SSD/XML exams in the previous semesters where candidates got their "project description" and worked about 20 minutes to prepare alone).
  • We should always have a test session some time before the exam.
  • We will (if we don't forget it) do recordings of the exam sessions.

Personal Offices

  • Create room with "Require Moderator Approval Before Joining" and publish the link address does not work as intended.
  • Make appointment by mail, then a room is created, and only the required persons get the link.

Recordings from Previous Lectures

  • We try to keep the recordings available as long as possible (they might be deleted automatically by GWDG)
  • register for a lecture from a previous semester in StudIP (we extend the registration for previous semesters and make the participants list invisible (if we don't forget it).
    Then you find the meetings and the recordings (StudIP updates may close it due to misfunctions).
  • An introductory technical meeting about BBB in general and DBIS' use of BBB and RocketChat has been recorded in April 2020. It is available as follows: register for the lecture "Semistructured Data and XML" im SS2020. There is a meeting "dbis-testmeeting-xml+dd+sqlp-20-04-2020" with the recording.

IFI CIP Pool Computers

  • Access the IFI CIP Pool computers as usual via The pool computers may be physically turned off.
  • The eight shell virtual machines that cannot be turned off (CS I participants should already know them).