Definitions Rage
This post is was provoked by the (in places) poorly written article about consciousness formation in classical AI from the University of California, San Deigo. Most of my points about the article have or will be merged into my draft of almost the same title1. However, the lack of Comp Sci expertise on the paper was extremely apparent, and really got to me when they went on to butcher some of the most basic terms in the field.
That said, I've heard people in my department at Imperial (probably including myself) make the same mistakes, so I can't blame them that much...
| Analog[ue] | As an adjective, it indicates that the noun it modifies (such as the current time, length of an object) is "represented by a continuously variable physical quantity that can be measured2". |
| Discrete | As an antonym to analogue, it means that the thing being measured can only take a finite set of values. For example, the number of people in a room is discrete - you (hopefully) number have a non-integral number of people with you. |
| Digital | The word digital is often used as a synonym for 'encoded in a binary string'; however is actually refers to representing data with discrete values (as opposed to data actually having discrete values - you can still have a digital representation of an analogue value) |
| Binary | Being in a state of one of two mutually exclusive conditions such as on or off, true or false, presence or absence of a signal. One binary value, called a binary digit (or bit) can be in either state. The word binary is often conflated with a binary string - a series of bits which, when read in a particular way, represent some more complex information |
Now, all four of these words are adjectives (despite the best attempts of some writers to use them as nouns), and they all have very different meanings. Strictly speaking, both the examples I gave for analogue are wrong, as all physical properties are discrete - an aspect of the nature of quantum mechanics, where all properties are 'quantised' - or defined to be some multiple of the quantum, the indivisible unit of that . For example the quantum of light (and all electromagnetism) is the photon3. This means that any physical quantity can be expressed accurately as a binary string - except probability. And the problem with the nature of quantum mechanics is we can't know any of these values for certain, and these probabilities are not (to the best of my limited knowledge of the field) quantised in themselves.
Of course, you can imagine an entity which is a bit that also encodes it's probability information: a qubit. Photons can be used as qubits, with their polarisation indicating the probability of the value being a '1' or a '0'. This is the basis of quantum computer, a rather niche field even today.
Anyway, I digress. And my rage has now been calmed by the semi-hypnotic voice of Barack Obama.
- 1 ↑ Which will almost certainly never be published, as I can never get my thoughts down in a way that makes sense to both myself and other people. Also, my conclusions scare me on an existential level...
- 2 ↑ Adapted from http://en.wiktionary.org/wiki/analogue
- 3 ↑ And the quantum of solace is the smallest unit of consolation in bad times