|Hardware Artificial Life|
Layer contentsThe cellular automata on which HAL is based is made up of a number of largely independent layers with different functions. Two layers support universal computation and three layers are used for the transmission of heritable information from mother to daughter.
These are responsible for the transmission of heritable information between generations of cells. There are three such layers in the model, and information in these layers circulates around the organisms in an anti-clockwise direction.
Layer connectionsWhile the layers in the model operate largely independently of one another (which is what allows their description as separate layers) they are also connected to one another in a variety of ways.
Firstly, the developmental layer is responsible for the creation of the two calculation layers. It determined the shape and form of the cells by controlling the type and orientation of individual sites.
The second calculation layer takes inputs from the old DNA layer and from the first calculation layer. It processes the information it receives from these sources and as its outputs feeds the information into the developmental layer and the new DNA layer.
The first calculation layer is the main layer in the model which takes external connections. It receives information about target problems from outside the automata, processes this information, and then replies with proposed solutions. If these solutions are acceptable then the cell is allowed to continue to live.
This layer has only one way of communicating with the other layers of the automaton - it can transfer information to the second calculation layer.
Deliberately it receives no input at all from the rest of the automata once it has been created - indeed for all intents and purposes the rest of the automata might as well not exist. This has been done because under some circumstances, the rest of the automata will not, in fact, exist. In other words, the first calculation layer has been designed in such a way that it may be 'scraped off' the rest of the model and used independently of it. Evolved circuitry etched on this layer of a cell, or population of cells, can be largely divorced from all the reproductive machinery responsible for its creation, resulting in a much reduced component count.