HTTXPlugin V2.0


URL  : file://localhost/Work:Pgm/KT/doc/values.html
Title: Value Types in Istar



VALUE TYPES

In this version you are provided with the following basic value types from
which you can make attribute types.

Integer

   o Numeric for whole numbers
   o Range: -billion to billion (normal 32 bits)
   o Held as: 32 bits
   o Coding: simple signed binary number

Floating point

   o Numeric for floating point numbers
   o Range: normal 32 bits
   o Held as: 32 bits
   o Coding: normal exponent and mantissa

Ratio

   o Numerator and denominator, both can be signed
   o Used for any ratio
   o Range: Each part has range of full integer.
   o The ratio can represent infinity by holding denominator = 0
   o Held as: Two 32 bit integers
   o Coding: Two simple signed binary numbers; Infinity when denominator = 0
   o In most manipulations, the greatest common divisor is removed (so if you
     multiply 4/7 by 14/15 you get 8/15)

Odds

   o Numerator and denominator, both positive
   o Used especially for odds and conversions to and from probability
   o Used for bayesian multipliers
   o Range: Each part has range 0 to 65k
   o Held as: Two unsigned 16 bit words
   o Coding: Two simple unsigned binary numbers; Infinity when denominator =
     0
   o In most manipulations the greatest common divisor is removed

String

   o Any string
   o Range: up to 200 characters in length at present
   o Held as: child 'Sysatt' block with as much space as needed
   o Coding: ASCII

Boolean

   o Truth value: yes or no, true or false
   o Range: true or false
   o Held as: unsigned 16 bit word
   o Coding: 0 = false, anything else = true

Probability

   o 0 to 1 (0 to 100%) for soft truth value
   o Range: 0 to 1
   o Held as: Unsigned 16 bit word
   o Coding: 0x0000 means 0, 0xffff means 1

Bayesian

   o Probability used for evidential reasoning
   o Has a-priori and lower and upper cut-offs
   o Range: Part as probability
   o Held as: Four probabilities
   o Coding: As probability, four times

Proportion

   o Represents a proportion 0 to 100%
   o Used for anything that requires a limit of 100%
   o Range: 0 to 100%
   o Held as: Unsigned 16 bit word
   o Coding: 0xffff means 100%
   o In many things proportion and probability are interchangeable

OZMO

     (one-zero-minus-one, e.g. result of cosine)
   o Like a proportion that can go negative as well as positive
   o Used for e.g. degrees of belief, degrees of dislike
   o Range: -1 to 0 to 1
   o Held as: Signed 32 bit word,
   o Coding: 0x80000000 means -1, 0 means 0, 0x7fFFffFF means 1

Direction/Angle

     (0 to 360 degrees)
   o A circular value which represents proportion round a circle
   o Used for angles, directions, etc.
   o Range: 0 to 360 degrees (2.pi radians)
   o Held as: Unsigned 16 bit word
   o Coding: 0x0000 = 0 and 360 degrees. 0xffff = just before 360, 90 degrees
     = 0x4000, 180 degrees = 0x8000, etc.

Enumerated Type

   o An index number for selecting an entity from a set
   o See also Ordinal, which is ordered
   o Strictly, numeric comparisons and operations meaningless, but in
     practice allowed as for Ordinal
   o Range: strictly meaningless
   o Each value is expected to have an attached string name
   o Held as: Unsigned 16 bit word
   o Coding: 0 means 'nothing selected', 1 upwards shows selection

Ordinal

   o An index number for selecting an entiry from a list
   o See also Enum, which is unordered
   o Numeric comparisons and operations meaningful
   o Range: 1 to 65k
   o Each value can be linked to an attached string name
   o Held as: Unsigned 16 bit word
   o Coding: 1 = first in list, 2 = second, etc. 0 = 'nothing selected'

Block

   o The DSAP of a block in the KB
   o Used for identifying things in the KB and e.g. getting name of it
   o Its value must never be altered as it is like a pointer
   o Range: strictly meaningless
   o Coding: 32 bit relative pointer

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Copyright (c) Andrew Basden 1997.