Guide to exercise 4 Part 1 Boolean algebra

Guide to exercise 4 Part 1: Boolean algebra & Venn diagrams Part 2: Starting Scopus Tefko Saracevic 1

Part 1 Boolean algebra and Venn diagrams For practice; nothing to deliver; solution to the riddle on page 9 can be brought up in discussion © Tefko Saracevic 2

Definitions Boolean algebra • Algebra that operates on sets – unlike the regular algebra that operates on numbers • but has a similar basic operations • It has 4 basic operations – – unary: single set A intersection: A AND B union: A OR B negation: A NOT B Venn diagrams • Pictorial representations for Boolean algebra operations • Useful to envision or represent sets to be retrieved – e. g. : Venn diagram for A AND B is shaded area: • These can be combined © Tefko Saracevic 3

Boolean algebra: why important? • It is an algebra with well defined formalism & widely used in many domains and for many applications • Also used as a basis for computing • Since computers operate on sets, it was adapted for use in searching for documents (and other information objects) © Tefko Saracevic • In searching we ask a computer to look for sets of documents that have various combinations of terms or other attributes • Thus searches have to follow rules of Boolean algebra – advance searches can exploit capabilities of this algebra to pursue more effective searching, particularly in complex searches 4

Use of Venn diagrams • This is a Venn diagram with numbered sets; on next pages also with a number of search statements – use to shade sets obtained for given operations • for each statement shade the appropriate set or sets – e. g. for A AND B the sets are 2, 5 – for (A OR B) AND C the sets are 4, 5, 6 © Tefko Saracevic A B 2 3 1 4 5 6 7 C 5

For practice on exercises on following slides A B 2 3 1 4 5 6 7 C Tefko Saracevic 6

But watch out • A AND B OR C – cannot be computed any more than 2 + 3 x 4 can – because (2 + 3) x 4 gets different results than 2 + (3 x 4) • Thus it has to be either (A AND B) OR C or A AND (B OR C) – each results in different sets: first: 2, 5, 4, 6, 7 second: 2, 4, 5 © Tefko Saracevic • Shade them on the Venn diagram A B 1 2 4 5 3 6 7 C 7

Exercise – shade these sets (answers on the next slide) 1. A AND B 2. A OR B 3. A OR B AND C 4. (A OR B) AND C 5. A AND B NOT C 6. A AND (B NOT C) 7. (A AND B) NOT C 8. (A NOT B) AND C 9. A NOT (B AND C) 10. A NOT B AND C A B 1 2 4 5 3 6 7 C 11. A AND (B OR C) 12. A AND B OR C 13. A OR (B AND C) 14. A OR B OR C 15 A AND B AND C © Tefko Saracevic 8

Here are the answers … but one of them is wrong. Which one? 1. A AND B 2, 5 2. A OR B 1, 2, 3, 4, 5, 6 3. A OR B AND C 1, 2, 4, 5, 6 4. (A OR B) AND C 4, 5, 6 5. A AND B NOT C 2 6. A AND (B NOT C) 2 7. (A AND B) NOT C 2 8. (A NOT B) AND C 4 9. A NOT (B AND C) 6 10. A NOT B AND C 4 11. A AND (B OR C) 2, 4, 5 12. A AND B OR C 2, 4, 5, 6, 7 13. A OR (B AND C) 1, 2, 4, 5, 6 14. A OR B OR C 1, 2, 3, 4, 5, 6, 7 15 A AND B AND C 5 © Tefko Saracevic A B 1 2 4 5 3 6 7 C 9

Well… Also a Venn diagram From: angelfire. com now deceased; taken over by lycos, now at http: //www. ang elfire. lycos. co m/ © Tefko Saracevic 10

Explanation: © Tefko Saracevic • This Venn diagram is color-coded in order to demonstrate the way in which the layers overlap-if you are not familiar with the way colors are mixed subtractively just enjoy all the pretty colors. Not all Venn diagrams are color-coded. • Each circle is clearly labeled with the name of a character in bold letters. The qualities of that character are then written in that circle. • Some qualities are in an area where two circles overlap because both characters share those qualities. For instance, both the Tazmanian Devil and Wile E. Coyote are mammals, so "mammal" goes in the purple area where the circles of the two characters overlap. • In the center, all the circles overlap; qualities in this area this are shared by all three characters. For instance, Elmer Fudd, Wile E. Coyote, and the Tazmanian Devil were all in the movie Space Jam, so "Space Jam is written in the area where all the circles overlap. 11

Part 2 Introduction to Scopus © Tefko Saracevic 12

Comparison Dialog Scopus • Many databases; selection which to search needed • Much more content overall • Mostly command driven • One database; selection as to areas to limit • Menu driven – limited menu possibilities • A lot of field options by command • Not really transparent • Unwieldy © Tefko Saracevic – but commands executed & shown, could be manipulated • Many more options on fields, sources, outputs, saves … • Author, sources elaboration – citation tracking • Much more transparent • Wieldy 13

Opening screen: examine choices © Tefko Saracevic 14

First search – same topic as in Dialog but some limits © Tefko Saracevic

Result page: examine for further choices in refining query Your query shows what fields were generated for your query © Tefko Saracevic 16

Results: examine for choices and refinements; note that you can download selected documents or click to show Abstract © Tefko Saracevic 17

Click on one of the articles retrieved Results: examine for options. Follow up some e. g. journals In output you can get a full citation for bibliography © Tefko Saracevic 18