Representation Flashcards
How does information get codes
Reality consists of entities which are input into a data model through representations. These are represented as features and machine code identifies these features in binary form.
Give an example of bad representation
Evacuation maps using road maps and flood maps using river channels. Natural geography not represented in urban form
What is representation?
What is communicated is a representation of the physical world
Location in time and space reduced to symbols
Communication requires generalisation and abstraction
We have no direct access to the real world
How is information represented digitally
Most communication is digital
- sent through a pipe or transmission channel that sends ones and zeros
- stored on devices that only store ones and zeros
- word processors use ASCII
What is digital
Character and counting system
Can represent 0-9, A-Z, a-z.
Reduced to 0 and 1
Enter decimal 23 into binary
[12^4] + [02^3] + [12^1] + [12^0]
What is analogue information
Information expressed by scaling quatitaties
Good for quantitative information
Paper map is analogue
What is digital information
Information expressed by symbols
Requires a coding scheme of representation
Sender and receiver must agree on the scheme
What is ASCII?
American Standard Code for Information Interchange
26 letters plus common symbols
Originally 128 extended to 256
8 binary digits one byte per character
Includes control characters
Used 1960
Today: Unicode
Primitive data types in programming
Byte, 1 signed byte, values range from -128 117
Integer, double and char
What if you recieved the message in Boolean
First identify the data type - identify how many bytes Split into bytes Convert to hex Use information interchange to run code into identify messages
How are Feature types represented?
Feature types, such as trails, or individual features are represented by symbols on a map
For instance, in cartography a collection of symbols forms a legend, which associates each symbol with a type of feature.
These symbols should not be confused with conceptualisation of our environment
Features being depicted by dashed lines are not physical entities but artificats of human cognition
What is semantic operability
Triangle between
Thought or reference - ‘symbolised by’ - symbol - ‘refers to (other causal relations) - referent - ‘standing for (an imputed relation’
How is geographic information
X location in space-time
Z property
Z(x) is the value of that property at x
Missing is the provanance
P said
