CP2022 - Lecture 5 Information structure and encoding

1. CP2022 - Lecture 5Information structure and encoding

2. Information • What is information? • How is it • derived? • communicated? • used? • Any event produces information • much of this is now stored as • text, image, audio, video and in databases

3. Information • Users of information often have many choices but some restrictions • bandwidth • access equipment • physical proximity • cost considerations etc. • Is the information of the right type? • will it provide what is required?

4. Horse Race example Towcester - Going Soft 4.10 Hartford Handicap Chase 3m 1f £3,849 (5 declared) 1 1-1F13 Kilmington (29) J Gifford 9-11-10……………………..………..P Hide 2 -32443 Texan Baby (BEL) (7) N Twiston-Davies 9-11-5…….C Llewellyn 3 PP3UP Ballydougan (10) (CD) R Matthew 10-10-8……...……..S Curran * 4 5-24P3 Gold Pigeon (9) (D) B Rothwell 9-10-0……….…..Mr S Durack (5) 5 1F4022 Steeple Jack (43) K Bishop 11-10-0……………………….....R Greene Betting: 6-4 Texan Baby, 7-4 Kilmington, 4-1 Steeple Jack, 8-1 Gold Pigeon, 25-1 Ballydougan

5. More horse race information • A typical result would be: TOWCESTER 4:10 (3m 1f): 1, Ballydougan, S Curran (16-1) ; 2,Kilmington, (15-8 Fav); 3, Texan Baby(BEL), (5-2). 5 ran. 22, dist. (R Matthew) Tote: £20.40; £3.30, £1.10. Dual Forecast: £20.00. CSF; £43.30. • Full interpretation requires contextual information • (Show example video if possible)

6. Information structure • Example horse race information • Only the basic information is presented • There is only an indication of 6 previous runs • No information of what events were attempted • No indication of previous opposition • No information on preferred • distance, going, race type, course etc. • Little evidence in the result of what happened except the outcome • More information from a video recording or more detailed comments

7. Channel considerations • Video information needs a high bandwidth channel (e.g. satellite broadcast of horse race) • Audio could be used over lower bandwidth channel but some information is lost • Picture/text can be used in newspapers and • Text only on Teletext and computer stored information • Databases are used to store information for later retrieval • Indexed on • horse name, race time/date, jockey, trainer etc. • Multimedia would aid in the dissemination of this information - appropriate info for user’s access device

8. Information structure • Raw data contains information • This information will contain structure If more data is available then.. more information should be able to be extracted (some data may be no use - e.g. blank video screen) • Some information structures are better related to one medium than others • Information can usually be extracted to suit most media • E.g. A video can be processed to give • still images, audio extract, text synopsis • All result in loss of information

9. Information structure in computers

10. Structure • The levels may each have a different encoding and structure • This may impose restrictions on • information storage and retrieval or • performance • Good quality systems should not restrict the information requirements • Example • Distributed storage of WWW pages restricts access time • Coding restricts date information - Y2K problem?

11. Encoding • Most appropriate encoding determined by • structure of the information • user’s need and intended use as an example - consider different maps - each scale has a different level of detail but could all be generated from the same GIS • available channels • Available channel will determine the scope of the information that can be communicated • limits to quality, response time, usability etc. • User’s needs example - Horse race information • gambler needs only the result • trainer may need video or more detailed text/audio

12. Encoded information objects

13. Text • ASCII uses 7-bits per character • Efficient storage and transmission • uses a limited symbol set (26+26 + punctuation) • Only applies to English • Other versions can be used for other symbol sets • New encoding of text based on Unicode • a 16-bit system that encompasses all language symbols

14. ASCII

15. Structured information • Structured information can be very efficient • Structure imparts meaning • this is easier than with free text • example - 29 WV1 1LL could be used to retrieve an address • There can be problems • querying databases can produce masses of data unless the query is specified to exact limits • Example A driver database could be queried for a John Smith in Wolverhampton but would produce a large response if the Wolverhampton is missed out of the specification of the query.

16. Audio • Audio information has many different standards • Some of the differences are due to differing requirements of systems • Two common standards • CD-quality stereo audio and mono speech quality A. CD uses 44.1 kHz sampling, 2 x 16 bit channels = 44 100 x 16 x 2 = 1 411 200 bps B. Mono speech uses 8 kHz sampling on 1 x 8-bit channel = 8000 x 8 x 1 = 64 000 bps (ISDN rate!)

17. Image • Two main types of image • bit-mapped or graphic images • bit-mapped are generally pictures • graphic images are generally line drawings or graphic designs • Each has different storage and transmission requirements

18. Image 2 • Diverse set of standards • JPEG is commonly used and a robust, open, international standard • others are GIF, TIFF, TGA, etc…..

19. Video • The most complex of multimedia types • Transmission and storage requirements determined by • Frame rate (15-30 is common) • Size of display (can be changed to suit transmission rate) • Resolution used (can be determined by display) • Colour depth (depends on requirements 8-24 bit) • Typical figures Video conferencing quality 15 fps, 160 x 120 pixel window, 16 colours = 15 x 160 x 120 x 4 = 1 152 000 bps (about 1Mbps)

20. Summary • Information has inherent structure • Structure can • be used to simplify storage or transmission requirements (results) • reduce usefulness (Y2K) • Different information types have different transmission requirements • Information types should be used to suit user needs channel available, information need, other requirements.