1 CP Lecture 5 Information 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) 11-1F13 Kilmington (29) J Gifford ……………………..………..P Hide Texan Baby (BEL) (7) N Twiston-Davies …….C Llewellyn 3 PP3UP Ballydougan (10) (CD) R Matthew ……...……..S Curran * P3 Gold Pigeon (9) (D) B Rothwell ……….…..Mr S Durack (5) 5 1F4022 Steeple Jack (43) K Bishop ……………………….....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: £ CSF; £ 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 ( 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 = x 16 x 2 = bps B. Mono speech uses 8 kHz sampling on 1 x 8-bit channel = 8000 x 8 x 1 = 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 = 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.