e Cognition Model Components Model Components Variables and
e. Cognition Model Components
Model Components • Variables and Constants • Operators and Functions • Links • Logical States • Messages • Change Storage 2. e. Cognition Model Components 1
A Simple Example a+b=c If this is part of a larger model, how is it controlled? What does the EQUALS mean? How many ways should we be able to use this piece of knowledge? 2. e. Cognition Model Components 2
A new approach to knowledge Instead of writing programs, turn the knowledge itself into a computing machine a+b=c Structure Programmatic: if input(a) and input(b) then c = a+b else if input(a) and input(c) then b = c-a else… NYK - Not Yet Known 2. e. Cognition Model Components 3
Use the structure itself a+b=c Values flow through the structure in any direction. The EQUALS operator allows for logical control. 2. e. Cognition Model Components 4
Information Coming the Other Way Example: a + b = c We have a range on one variable, producing a range on another. 2. e. Cognition Model Components 5
Is It Just Numbers The structure can propagate a wide range of entities through its connections, and the operators can be operating on analytic or experiential information, and the structure can be changing itself - it is a lot more than just numbers. 2. e. Cognition Model Components 6
Variables and Constants Every variable and constant has a logical state and may have a value - logical, numerical, string, list, object. Every variable and constant is a linkable object - it can support unlimited connections. Variables are addressable by a name which can have unlimited depth of context and multiple context Model. Animal. Mammal. Whale. Moby. Dick 2. e. Cognition Model Components 7
Operators & Functions The distinction between the two in the network is blurred • many functions are invertible - ABS(X) • many functions are actually pieces of network machinery - WHILE, GETPUT, SEQUENCE Operators have a fixed orientation to their connections (the number of connections may be variable the PLUS operator can function with up to 1024 connections). 2. e. Cognition Model Components 8
Operators & Functions The network has operators that are not obvious in the text • SPINE and LEVEL operators allow logical structuring of network text • INDEX operator to represent an index into a list • structure to represent potential inferences Some textual representations convert to simpler forms • Minus is a Plus operator with different orientation • a + b + c is held in the network as one operator 2. e. Cognition Model Components 9
Links connect operators and variables together. They store the information produced by operators, allowing an operator to have many concurrent outputs. Links provide for bi-directional flow of information. Operators can add links to themselves for storage of states, or an operator’s only purpose can be to add links to other operators - LISTLINK. 2. e. Cognition Model Components 10
Logical States Logical states range over • • • Not Yet Known Unknowable - Bayesian values or existence Error False True and control the phasing of operations 2. e. Cognition Model Components 11
Messages can be • simple singular values - True, 2. 3, “Fred” • objects - Joe, Moby. Dick, Glock • lists - {1, 2, 3} • Bayesian values - UKE 0. 7 • signalling nonexistence of structure • alternative values using list transmission - 2. . 4, 3<->6 • structure - a < b, IF X > Y THEN P < Q There is no conceptual limit on the size of a message, as it is constructed out of the same elements that make up the network 2. e. Cognition Model Components 12
Self Modification X = + List Link A% B X = + List Link A% = B=9 B X=5 X = + 2. e. Cognition Model Components C D C=3 C D=-7 D 13
Change Storage All changes to the network can be stored in memory in a layered fashion for later retrieval. This allows values to be changed or hypothetical structure to be generated, its operation observed, and then the scenario to be undone. A change can be attempted, and if successful, its changes merged with a previous store level which is still tentative. 2. e. Cognition Model Components 14
Functions and Operators • e. Cognition provides a comprehensive set of predefined operators and functions. • The operators in the network represent the elemental or atomic level of analysis • Each operator determines its own activity, so the network is micro-scheduling what it does. • The user can add script operators, and user-defined functions. 2. e. Cognition Model Components 15
Handling Uncertainty • e. Cognition is designed to handle uncertainty – it can reason using partial or fuzzy knowledge. • Variables can hold tentative knowledge – alternative values (ranges for numbers) or distributions. • Logical variables can support values between False and True (0 to 1 is used, with 0. 5 representing Unknowable). These intermediate values can be overridden, but True and False cannot be overridden. 2. e. Cognition Model Components 16
How It Works • Setting the value of a variable causes the new value to propagate in all directions through the network, until there are no new paths to propagate • Ranges of numbers, alternative strings and lists are also propagated • Some operators alter their local topology and then destroy themselves • Spreading activation is also used - one operator forces another to become active, as the message is too complex to propagate 2. e. Cognition Model Components 17
Logical Control • Everything has a logical state • Every statement or equation lives in a logical “block”, or environment, and is controlled by a “head” variable • A head variable can turn its block on, make it false or unknown, or make it go dark • A head variable can be tested for truth (higher structures are invertible too) • Logical control allows the user, and the model itself, to control which part of the structure is active 2. e. Cognition Model Components 18
- Slides: 19