## Error in Moed B grading | |

anyone who used the "exists" operator in the XQuery question and lost points for that is requested to send their exam to Omer during the next week. |

29/10/2013, 18:21:33 |

## Moed B appeals | |

If you wish to appeal you may do so by sending Omer (either by email to omerkatzcs.technion.ac.il or you can put it in his mail box on the 5th floor) a written appeal. Your appeal should include a copy of your (scanned) exam and an elaborate explanation of your appeal (why you think you should have gotten more points). All appeals should be submitted by the end of the month (31st of October, 23:55). Keep in mind that when you appeal your entire exam may be rechecked and not just the questions you mentioned in your appeal. |

14/10/2013, 18:25:46 |

## Moed B grades are published | |

You can find the exam and it's solution in the "previous exams" folder under "additional files" in the "course material" section. |

14/10/2013, 18:24:15 |

## Moed A appeals | |

The exams have been scanned. If you wish to appeal you may do so by sending Omer (either by email to uomerkatzatcs.technion.ac.il or you can put it in his mail box on the 5th floor) a written appeal. Your appeal should include a copy of your (scanned) exam and an elaborate explanation of your appeal (why you think you should have gotten more points). All appeals should be submitted by the 30th of July (next Tuesday) by 23:55. Keep in mind that when you appeal your entire exam may be rechecked and not just the questions you mentioned in your appeal. |

22/7/2013, 21:04:25 |

## Moed A grades are published | |

You can find the exam and it's solution in the "previous exams" folder under "additional files" in the "course material" section. The exams will be returned to the secretaries next week. |

18/7/2013, 19:20:15 |

## pre-exam office hours | |

Omer's office hours will be on Wednesday at 10:30 |

9/7/2013, 00:23:33 |

## pre-exam office hours | |

Daniel will be available on Monday at 15:00. Omer will be available Wednesday afternoon (specific hour will be published later). |

7/7/2013, 00:17:47 |

## HW4 grades are published | |

Also, the solutions to HW3 and HW4 are online |

5/7/2013, 16:03:06 |

## HW2 resubmission grades are published |

5/7/2013, 14:38:21 |

## HW3 grades are published |

1/7/2013, 10:35:18 |

## Daniel's office hour this week | |

Daniel's office hour this week will be on Sunday at 12:30 |

29/6/2013, 13:55:02 |

## Assignment 2 resubmissions | |

We have decided to allow you to fix and resubmit your solutions under the following guidelines: 1) The deadline for resubmissions is the 2.7 23:55. 2) All resubmissions should be sent by email to Omer 3) Your new grade will be at most 85% of the grade obtained by automatic testing. 4) Your new solution can differ from your old solution by at most 5 lines. 5) All late submission penalties from the original submissions still apply. Any resubmissions that do not follow any of the above guidelines will be checked. |

24/6/2013, 18:56:25 |

## Last lecture of the semester | |

On the 30.6 we will have the final lecture of the semestrer. Instead of a regular lecture we will a special guest lecture. The lecture will be Professor Yaron Kanza. Below is an abstract for his lecture: אינטגרציה של מידע: על הכוח ועל הסכנות שבחיבור מידע ממסדי נתונים שונים ליכולת לחבר מידע ממקורות שונים חשיבות הולכת וגדלה בעולם שבו למידע חשיבות הולכת וגדלה ושבו מקורות המידע הולכים ונעשים מפוזרים ומגוונים יותר ויותר. למשל, מערכת להשוואת מחירי מוצרים צריכה להביא את מחירי המוצרים ממספר מקורות שונים ולצרף את המידע בהתבסס על זהות המוצרים. לצירוף המידע, במקרים כאלו, חשיבות רבה כי ניתן לדעת לא רק את מחיר המוצר בכל מקום בנפרד אלא גם לערוך השוואה של מחירי המוצרים. אולם כיצד לצרף מידע ממקורות שונים בצורה נכונה זוהי בעיה קשה. לצורך המחשה, מוצרים עשויים להופיע בשמות שונים במקורות השונים, מחירי המוצרים עשויים להיות נקובים במטבעות שונים, ומאידך, מוצרים בעלי שם זהה במקורות השונים עשויים להיות שונים זה מזה במקורות השונים. יתר על כן, צירוף מידע גם עלול להוביל לבעיות פרטיות. פרשת המעקבים שנחשפה לאחרונה ושבה סוכנויות ביון של ארה"ב אספו מידע על אזרחי ארה"ב זו דוגמה עדכנית לכך. בהרצאה נסקור את הנושא של אינטגרציה של מידע. נבחן את הרקע ההיסטורי של הבעיה ונדון בחשיבות האינטגרציה לצרכים שונים. נבחן ביתר פירוט את הבעיות שעולות באינטגרציה של מידע וכיוונים שונים לפתרון. כמו כן, נדון בשאלת הפרטיות שעולה מאינטגרציה של מידע ובמספר דרכים להתמודד עם בעיית הפרטיות. לא נדרש ידע מעבר לידע שנלמד בקורס מסדי נתונים. |

19/6/2013, 12:38:37 |

## HW2 grades are published | |

The tests are available in the assignment section. Tests 1-10 are worth 4 points. Tests 11-18 are worth 7 points. The example test that you were given with the assignment is also worth 4 points. (Some tests have 2 solutions, corresponding to the possible choices in InterestingTags) We overlooked most minor coding and SQL mistakes and bad practices. Some students did not follow the restrictions in the assignment. If you created new tables, reset the tables at the beginning of your code or didn't drop your views, you lost 10 points. Also, I would like to remind everyone that (as stated in the FAQ) unapproved late submissions are forbidden in this course. We decided to go easy on you and if you submitted late without prior approval you lost 5 points for every 12 hours that passed. This will probably also be the way late submissions are dealt with in the 3rd assignment but not in the 4th. Unapproved late submission in the 4th assignment will not be checked. |

16/6/2013, 23:43:49 |

## Omer's office hour this week | |

Omer's office hour this week will be at 17:30 instead of 16:30 |

15/6/2013, 18:10:31 |

## HW4 FAQ is online |

13/6/2013, 13:09:10 |

## Correction to HW4 | |

There was a question missing from the homework (Q2f). Corrected version was uploaded. Make sure you don't miss it. |

11/6/2013, 17:05:22 |

## HW4 is published |

10/6/2013, 11:42:42 |

## experimenting with XPath | |

you can use the following website to experiment with XPath queries: http://www.whitebeam.org/library/guide/TechNotes/xpathtestbed.rhtm upload your xml file to the site and you will be able to see which elements are returned by each query |

4/6/2013, 18:12:22 |

## XML tools | |

for those of you who are using notepad++: notepad++'s xml tools plugin offers useful and easy to use tools to check, verify and validate your xml and dtd files. you may use it in your work. |

4/6/2013, 18:12:10 |

## Abstract Lecture 9 (June 2) | |

Decomposition of relation schemes (R[U], F) with U a set of attributes and F a set of FD's. We discuss possible decomposition of R[CSZ] a) with no FD's b) with F = { Z->C, CS->Z }. We introduce the notion of information preserving decomposition. We prove: Theorem: Given R[U], with FD's F, and a decomposition R[U_1], R[_2]. 1) For the decomposition to be information preserving we need U_1 and U_2 have a non-empty intersection V. 2) The decomposition is information preserving iff eithera F |= V->U_1 or F |= V->U_2. We introduce the projection of FD's P_U(F). We illustrate the following Theorem (not previously taught): Theorem: Given R[U], with F, and a decomposition into several relation schemes R_1[U_1], R_2[U_2], ..., R_m[U_m]. Assume further that a) The union U_{i=1}^{m} P_U_i(F) |= F, and b) some U_i is a superkey, i.e. F|= U_i -> U. Then the decomposition is information preserving. In Lecture 10 we prove Armstrong's Theorem: F|- X-> Y iff F|= X-> Y and algorithms for computing F+ and X+, and, possibly, start with Normal forms of relation schemes with respect to a set F of FD's (BCNF and 3NF) |

4/6/2013, 11:46:53 |

## Abstract Lecture 8 (May 19) | |

Functional dependecies. Syntax of FD's. Semantics of FD's. Consequence relation F|= X -> Y between a set F of FD's and an FD X->Y. Armstrong axioms and rules. F |- X -> Y stands for X->Y is Armstrong provable from F. Examples and additional rules. Statement of Armstrong's Theorem: F |- X -> Y iff F |= X -> Y. Proof delayed. Slides from previous semesters, but in different order. |

4/6/2013, 11:46:27 |

## Abstract Lecture 7 (May 12) | |

Datalog; Basically the slides from previous semesters. |

4/6/2013, 11:46:05 |

## Abstract Lecture 6 (May 5) | |

Safety: The slides from http://webcourse.cs.technion.ac.il/236363/Spring2013/ho/WCFiles/safety-12-13.pdf |

4/6/2013, 11:45:43 |

## Correction to previous announcement | |

Omer's office hour tomorrow (4.6.13) will be at 18:00 |

3/6/2013, 16:27:08 |

## Omer's office hour this week | |

Omer's office hours this week (4/6/13) will at 17:30 instead of 16:30 |

2/6/2013, 22:21:43 |

## HW3 FAQ is online |

27/5/2013, 12:28:58 |

## Dates in HW2 | |

You can relax. We will not use dates starting with 0 (such as 10-01-2013) in our tests. |

26/5/2013, 17:53:19 |

## HW3 is published |

26/5/2013, 17:49:31 |

## A note about InterestingTags in HW2 | |

To make things a bit easier for you we've decided to give you a choice. When encountering a question with no answers you may choose one of the following options: 1) count the question when calculating the tag's score and print the tag with number of answers 0. 2) don't count the question and don't print the question. Choose which option you prefer. |

21/5/2013, 14:44:06 |

## HW2 postponed | |

Due to connectivity problems in the server (dropped connections, etc.), submission of HW2 is postponed to Sunday. The server problems cannot be fixed without a restart (which will take a lot of time, possibly 24 hours). To allow you all to properly check your solutions, we will not fix it now. Instead we postpone the deadline. Don't wait until the last moment to check your solution. Further delays and postponements due to server connectivity issues will not be approved! If you got permission to submit late, you may add the number of days approved to the new deadline. Also, be sure to check that you have read all posts on the FAQ. |

21/5/2013, 13:07:33 |

## HW1 solution is published |

20/5/2013, 16:19:29 |

## HW1 grades are published | |

Some students submitted alone without approval. This time we did not deduct points for that. Next time you will lose points (if you a valid a reason for submitting alone you need to contact the TA in charge and get his approval). Also, there were a couple of students who did not enroll to the course site and therefore we cannot enter their grades. If you submitted the homework but did not get a grade, make sure that you are enrolled to the course site and contact the TA in charge. |

19/5/2013, 18:41:21 |

## Error in HW2 Example.sol | |

there was an error in the example solution we gave you. the corrected version has been uploaded to the site. also, any time we find frequently asked questions or we need to exp[lain or clarify something we do that in the FAQ section so make sure you read frequently. |

2/5/2013, 19:06:48 |

## Omer's office hour today | |

Due to unexpected circumstances Omer's office hours today will be postponed to tomorrow (Wednesday) at 17:30 |

30/4/2013, 14:44:40 |

## New DRC/RA slides available online | |

We've uploaded new slides regarding the differences and similarities between queries in DRC and queries in RA. These slides are also an example for translating queries from one language to another. The slides are available in the supporting slides section |

29/4/2013, 10:39:37 |

## HW2 FAQ is online |

23/4/2013, 17:42:45 |

## Abstract Lecture 5 | |

We discussed extensively the queries of slides http://webcourse.cs.technion.ac.il/236363/Spring2013/ho/WCFiles/Logic%20%28DRC%29%20vs%20RA.pdf We discussed the relationship between RA and SQL Slides at http://webcourse.cs.technion.ac.il/236363/Spring2013/ho/WCFiles/2b_DBMStut-RA_BasicSQL.ppt http://webcourse.cs.technion.ac.il/236363/Spring2013/ho/WCFiles/2b_DBMStut-RA_BasicSQL.pdf We gave a formal definition of DRC and introduced the notion of Domain independence. We show by induction that queries in RA are domain independent, and showed that complementation (Negation) in DRC leads to queries which are domain dependent. Lecture 6 will deal with safe range formulas http://webcourse.cs.technion.ac.il/236363/Spring2013/ho/WCFiles/safety-12-13.pdf |

29/4/2013, 17:07:52 |

## Abstract Lecture 4 | |

We discussed the use of division in Relational Algebra. We introduced DERC (informally) and translated division into DRC Slides at http://webcourse.cs.technion.ac.il/236363/Spring2013/ho/WCFiles/Division.pdf |

22/4/2013, 16:43:10 |

## HW2 is published |

21/4/2013, 19:18:20 |

## Daniel tutorial next week | |

As previously announced, the tutorial will on Wednesday at 13:30 instead of its usual time. The tutorial will be in classroom Taub 6. |

10/4/2013, 20:26:50 |

## Abstract Lecture 3 | |

We introduced relational algebra (RA) following essentially the slides of previous lectures on relational algebra (slides 1-14). Basic operations: Projection, Cartesian product, selection, union, intersection, set difference, and renaming. In selection only boolean combinations of equalities and comparisons are allowed. We discussed additional examples: 1. Different realizations of of ER-diagrams, rather than our standard interpretation. 2. A database with a "direct ancestor relation (DA)" only. We discussed queries defining various family relations such as "brother", "granadfather", "cousin", "n-th cousin k-removed", etc. The examples from slides 19-24 should be studied as homework. We also discussed proving independence of the basic operations: cartesian products (projection) cannot be expressed with the remaining basic operations. Intersection can be expressed with the remaining basic operations. We left as an exercise: Show that set difference cannot be expressed with the remaing basic operations. Next lecture: More on RA, comparing RA and basic SQL. |

9/4/2013, 11:17:38 |

## Thursday tutorial on the 18th of April | |

Daniel will not be able to make it to the tutorial on Thursday 18/4. Instead Daniel will have a tutorial on Wednesday 17/4 at 13:30 (classroom will be announced later). This is a one time change! |

8/4/2013, 17:22:16 |

## HW1 FAQ is online | |

Corrections to the homework and answer to repeated questions will be posted in the FAQ. You should check it regularly and make sure you check it before submitting the homework. |

4/4/2013, 22:31:47 |

## HW1 is published |

1/4/2013, 22:57:54 |

## Abstract Lecture 2 | |

We completed the definition of the ER-diagrams (slides with diagram definitions) and discussed various examples partially take from the old course slides: Lecture 2 (ERD) After Pessach we start with query languages. The first will be relational algebra (RA). Previous abstracts can be found here: http://webcourse.cs.technion.ac.il/236363/Spring2013/en/ho_Abstracts%20&%20Supporting%20Slides.html |

20/3/2013, 14:58:49 |

## Lecture class | |

After the Passover break, all Lectures (only lectures, not tutorials) will be in Taub 7. |

17/3/2013, 16:26:23 |

## SQL server restart | |

Due to a permissions issue we had to completely restart the server. It is back online and you can now go ahead and create your users. The few students that have already created their users, unfortunately those users no longer exist so please recreate them. |

12/3/2013, 23:05:57 |

## Abstract Lecture 1 | |

Lecture 1 (10.3.2013) - General remarks about the course and its homepage. - Genral remark on learning and exams. - Exampes of large reslient database: Timetables of European train network, Insurance companies, Banks - Many of these were first designed even 50 years ago and evolve very slowly. - Introducing Entity-Relationship diagrams, I Entitities (autonomous tables) Relationships (tables linking Entities) Keys and Inclusions In Lecture 2 we will continue with Entity-Relationship diagrams. |

11/3/2013, 14:11:15 |

## Course material rearranged | |

We have rearranged the course material into 5 categories. You can find explanation about the categories in the course material section. Also, each week we will upload an abstract for that week's lecture so if you missed a lecture you will know what you have missed. |

8/3/2013, 20:22:35 |

## A few submission guidelines | |

1) All submissions should be in pairs, unless given written permission from the TA in charge. 2) All extension request must be submitted to the TA in charge at least 24 hours prior to hw submission. Any requests sent less than 24 hours before submission will be declined. 3) If you are given an extension, the submission hour stays the same. i.e if you were supposed to submit by 12:30 and was given a 1 day extension, you should submit by 12:30 the next day. 4) All late submissions (both approved and non-approved) should be submitted to the mail box of the TA in charge of the homework on the 5th floor (in time submission should be submitted to the course's mail box on the 1st floor). (late submission of the wet hw should be sent to the email address of the TA in charge of the homework) |

3/3/2013, 16:41:00 |

## 234293 as a Prerequisite | |

Students might need background in Logic for some parts of the course. Students that didn't take the prerequisite course 234293 are allowed to take the course, but they do so at their own risk (the risk being not knowing any logic). In such cases, we recommend reading book, notes and slides to reduce the risk. |

3/3/2013, 16:39:16 |

## SQL Accounts | |

Every student can now open an SQL account. An account allows you to practice SQL on sample tables, and is essential for testing your wet assignment. Please read the "SQL accounts" subsection in FAQ, where all details are provided, and make sure you indeed have an account. Good Luck! |

3/3/2013, 16:38:54 |

## Course Material | |

The presentations from the previous semester have been uploaded to the course site. They are currently relevant to this semester but that may change during the semester. |

3/3/2013, 16:38:37 |

## Welcome to Database System course | |

May we all have a fruitful and enjoyable semester, The course staff. |

3/3/2013, 16:37:45 |