Welcome to the Wiki page of the course Search Engines, WS 2009 / 2010. Lecturer: Hannah Bast. Tutorials: Marjan Celikik. Course web page: click here.

Exercise Sheet 1

Questions or comments below this line, most recent on top please

Sorry to bother you. I added the Link to exercise sheet 2 with the linked pdf. Needed this to find the sheet as fast as possible. Marius 29Oct 10:04 p.m.

Is there a webpage for exercise sheet 2 somewhere? Johannes 29Oct 07:45 pm

I am not able to view my page even after logging in. It says i am not allowed to view this page. My page name is PareshParadkarExcercises. Paresh 28Oct 11:30 am

Is there any result by now concerning an additional tutorial time schedule? The problem is, I've got a colliding lecture during the time of the exercise course, that I'd better not miss. E.g. Tuesdays at 4 p.m. would be fine, too. I don't know if there's anything planned, yet. Marius 27Oct 7:15pm

New deadline for the exercises: Tuesday, 14:00 Marjan 27Oct 2:56pm

I could not able to Create my page like donaldduckExcercise instruction shown in page. getting some error. ConvertError ExpatError: mismatched tag: line 376, column 881 (see dump in /usr/local/var/moin/farm/teaching/data/expaterror.log). Waleed Butt

To Johann + all: I briefly commented on the rules for the exercises in the first lecture and will talk about it again in the next lecture. The exercises are graded (one or two points per exercise), you will get a mark for them in the end, and that mark will be 40% of your final mark for the course (the other 60% will be an exam at the end, we'll see whether that will be oral or written). Groups work is not allowed (the point of the exercises is missed otherwise), and if you copy or otherwise cheat, you are out. You don't have to come to the lectures if you think you don't need it. You don't have to come to the tutorials if you think you don't need it. But you absolutely must do the exercises, and you must do them yourself. Hannah 26Oct09 2:02pm

To Johann + all: I am sorry but solving the exercises is mandatory, however attending the tutorials is not, i.e. if you understand everything there is no need for you to come to the tutorials. Marjan 26Oct 1:45pm

Notice: Please note that I recommend using English when producing your handouts. Please use German if you are absolutely not confident with English. In fact, either language is fine - it's just that there is a chance that I don't understand everything (if it's written in German). Thanks! Marjan 26Oct 1:41pm

Hi there, i don't know if i missed something but i also asked a fellow student who did not know! Are the Exercises mandatory and do we get some kind of points for them (where we need a specific amount to be allowed to participate the exam). I am asking because i don't know if i can finish all of the assigned tasks till tonight. Johann 26Oct09 1:39pm

Hi Claudius + all: it's up to you how many you compute, the more you can find the better. The obvious algorithm is of course to try out all pairs of words. This will find all pairs with one hit, but it's obviously a quadratic algorithm and so will take a very long time even for a relatively small collection. See if you can find a smarter algorithm. Be assured, there is one. Hannah 26Oct09 1:26pm

Hi! In Exercise 4: Do we have to compute all possible pairs of query-words with one hit or only one pair of words? Claudius 26Oct09 12:50am

To Björn: No, it does not. You do not need to include positional information in your inverted index. But you're right: indexes are usually positional and the Zipf's law refers to the size of the inverted lists when positions are included. Marjan 25Oct 7:45pm

Thank you for the response. Does this also concern the inverted index? I'm wondering because the slides only contain examples where the list of documents does not contain duplicate entries. Personally, I could imagine a practical use for both variants. That's why i'm asking. Thanks again in advance. Björn 25Oct09 7:20pm

Hi Björn + all: occurrence always means individual occurrence, that is, if a collection has two documents and the word x occurs once in the first document and twice in the second document then there are three occurrences of this word overall. Ok? Hannah 25Oct09 2:12pm

To Zhongjie + all: you are right, you can't add the #acl line to the document yourself, so I just did it for you. I will change the instructions on the upload page accordingly. Sorry for this initial confusion, but hey, good that we have a Wiki. Hannah 25Oct09 2:06pm

Hey everyone! Whenever the exercise is talking about frequencies and occurences. Does it talk about occurences in different documents or should we considre multiple occurences in the same document. Thanks a lot. Björn 25Oct09 12:49pm

To Johannes: How did you solve the problem? I have logged in my account as my name, and my email links only this account. But I still get the error message 'You can't change ACLs on this page since you have no admin rights on it! ' when I try to enter '#acl ZhongjieCai:read,write -All:read ' to the first line of the page... Zhongjie 25Oct09 01:15am

Problem solved. To everybody: don't try to create multiple users with the same e-mail address. Johannes 25Oct09 00:21am

Oh, I see, well that *must* be your user name. Sorry for not making that clear earlier. Please create an account with that user name and try again. Hannah 25Oct09 00:02am

No that is not my user name. Johannes 24Oct09 11:58pm

Hi Johannes, if you are logged in as JohannesStork you should be able to see it, did you try that? Hannah 24Oct09 11:59pm

I don't know if this is the right place to ask, but I can't access my exercise page. It says "Sie dürfen diese Seite nicht ansehen." Johannes 24Oct09 11:50pm

Good question, Johannes. Please upload the source code separately, either as a .zip or .tgz archive. I have modified the instructions on the upload page accordingly. Sorry if that means additional work for you, we weren't expecting anybody to submit so early ... Hannah 24Oct09 11:43pm

Shall we put the whole source into the PDF? What about tar.gz? Johannes 24Oct09 5:18pm

Hi Johannes + all, the slides are now availabe as PDF, see the link above. Hannah 23Oct09 17:04

Note about Exercise 5: One can assume that a more general model of the word frequencies is given than that given in the lecture, i.e. eps * N * (1 / i^alpha). Now both parameters (eps and alpha) can be estimated simultaneously. Marjan 23Oct09 3:29pm

Can you provide the slides as PDF? Johannes 23Oct09 10:05am

Please note that the deadline for uploading your solutions of the exercises is always Monday, 23:59 (sharp). Marjan 22Oct09 6:15pm

When you add a question or comment here, please end it with your name and the date and time in bold face, just like I did now. Hannah 22Oct09 01:59am