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LIS508 lecture 2

LIS508 lecture 2. Thomas Krichel 2003-10-07. today's lecture. Recap on what we did last week. Encoding mark-up Databases. Recap. Computers deal with on/off signals called bits. Collections of these bits are binary numbers.

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LIS508 lecture 2

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  1. LIS508 lecture 2 Thomas Krichel 2003-10-07

  2. today's lecture • Recap on what we did last week. • Encoding mark-up • Databases

  3. Recap • Computers deal with on/off signals called bits. • Collections of these bits are binary numbers. • Texts are (basically) strings of characters. To represent text, we need to represent characters. • To make a characters understandable to a computer we associate a number with each character. The result is a character set.

  4. Beyond characters • There is more to text than a string of characters. • There is layout • titles • abstracts • mathematical formula spacing

  5. Layout • Layout can be conveyed by additional text that has special meaning. Examples • LaTeX • HTML • PostScript • Another way is to do non-textual layout by adding some other digital signals. Examples • DVI • MS Word • MS Powerpoint These can not be shown in these slides!

  6. Example: LaTeX \bigskip\textbf{Class structure} Classes will be held in the computer lab in the Palmer School between 18:15 and 20:45. An optional practice session will last until 21:15. \begin{tabular}{@{}llll@{}} 0&2003--09--23&introduction to the course &\\ 1&2002--09--30&bits bytes and characters &\\ 2&2003--10--07&databases and markup languages&\\

  7. Example: HTML <p><strong>Class structure</strong><p>Classes will be held in the computer lab in the Palmer School between 18:15 and 20:45. An optional practice session will last until 21:15.<p>Class details: <p><center><table width=100% border=1> <tr><td align=left> 0 </td><td align=left> 2003&#8211;09&#8211;23 </td><td align=left><a href="lis508w03a-00.ppt">introduction to the course</a> </td></tr><tr><td align=left> 1 </td><td align=left> 2002&#8211;09&#8211;30 </td><td align=left><a href="lis508w03a-01.ppt">bits bytes and characters</a> </td>

  8. Example: PostScript Fc(Class)g(structur)o(e)-104 3956 y Fd(Classes)26b(will)g(be)e(held)g(in)h(the)f(computer)f(lab)i(in)f(the)h(P)o(almer)f(School)g(between)f(18:15)h(and)g(20:45.)36 b(An)25 b(optional)e(practice)h(session)-104 4055 y(will)d(last)g(until)f(21:15.)-104 4155 y(Class)i(details:)-104 4307 y(0)141 b(2003\22609\22623)94b(introduction)18 b(to)i(the)h(course)-104 4407 y(1)141 b(2002\22609\22630)94 b(bits)21 b(bytes)f(and)g(characters)-104 4507 y(2)141 b(2003\22610\22607)94 b(databases)20 b(and)g(markup)e(languages)-

  9. DVI (rendition, "class structure") 1659: fntnum27 current font is ptmb8t 1660: setchar67 h:=-820459+473168=-347291, hh:=-22 1661: setchar108 h:=-347291+182183=-165108, hh:=-10 1662: setchar97 h:=-165108+327680=162572, hh:=11 1663: setchar115 h:=162572+254928=417500, hh:=27 1664: setchar115 h:=417500+254928=672428, hh:=43 1665: right3 163840 h:=672428+163840=836268, hh:=53 1669: setchar115 h:=836268+254928=1091196, hh:=69 1670: setchar116 h:=1091196+218232=1309428, hh:=83 1671: setchar114 h:=1309428+290976=1600404, hh:=101 1672: setchar117 h:=1600404+364376=1964780, hh:=124 1673: setchar99 h:=1964780+290976=2255756, hh:=142 1674: setchar116 h:=2255756+218232=2473988, hh:=156 1675: setchar117 h:=2473988+364376=2838364, hh:=179 1676: setchar114 h:=2838364+290976=3129340, hh:=197 1677: right2 -11792 h:=3129340-11792=3117548, hh:=196 1680: setchar101 h:=3117548+290976=3408524, hh:=214

  10. Databases • Databases are collection of data with some organization to them. • The classic example is the relational database. • But not all database need to be relational databases.

  11. Relational databases • A relational database is a set of tables. There may be relations between the tables. • Each table has a number of record. Each record has a number of fields. • When the database is being set up, we fix • the size of each field • relationships between tables

  12. Example: Movie database ID | title | director | date M1 | Gone with the wind | F. Ford Coppola | 1963 M2 | Room with a view | Coppola, F Ford | 1985 M3 | High Noon | Woody Allan | 1974 M4 | Star Wars | Steve Spielberg | 1993 M5 | Alien | Allen, Woody | 1987 M6 | Blowing in the Wind | Spielberg, Steven | 1962 • Single table • No relations between tables, of course

  13. Problem with this database • All data wrong, but this is just for illustration. • Name covered inconsistently. There is no way to find films by Woody Allan without having to go through all spelling variations. • Mistakes are difficult to correct. We have to wade through all records, a masochist’s pleasure.

  14. Better movie database ID | title | director | year M1 | Gone with the wind | D1 | 1963 M2 | Room with a view | D1 | 1985 M3 | High Noon | D2 | 1974 M4 | Star Wars | D3 | 1993 M5 | Alien | D2 | 1987 M6 | Blowing in the Wind | D3 | 1962 ID | director name | birth year D1 | Ford Coppola, Francis | 1942 D2 | Allan, Woody | 1957 D3 | Spielberg, Steven | 1942

  15. Relational database • We have a one to many relationship between directors and film • Each film has one director • Each director has produced many films • Here it becomes possible for the computer • To know which films have been directed by Woody Allen • To find which films have been directed by a director born in 1942

  16. Many-to-many relationships • Each film has one director, but many actors star in it. Relationship between actors and films is a many to many relationship. • Here are a few actors ID | sex | actor name | birth year A1 | f | Brigitte Bardot | 1972 A2 | m | George Clooney | 1927 A3 | f | Marilyn Monroe | 1934

  17. Actor/Movie table actor id | movie id A1 | M4 A2 | M3 A3 | M2 A1 | M5 A1 | M3 A2 | M6 A3 | M4 … as many lines as required

  18. SQL • Once we have the relational database, we can ask sophisticated questions: • Which director has had the most female actors working for him? • In which years films have been shot that starred actors born between 1926 and 1935? • Such questions can be encoded in a language know as “structured query language” or SQL. All relational database vendors implement a dialect of SQL.

  19. databases in libraries • Relational databases dominate the world of structured data • But not so popular in libraries • Slow on very large databases (such as catalogs) • Library data has nasty ad-hoc relationships, e.g. • Translation of the first edition of a book • CD supplement that comes with the print version Difficult to deal with in a system where all relations and field have to be set up at the start, can not be changed easily later.

  20. http://openlib.org/home/krichel Thank you for your attention!

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