In this paper, I formulate a Continual Learning problem and propose a method named "Homeostatic Continual Learning" that enables an AI agent to learn continuously in a changing environment without catastrophic forgetting. The core of the method is to find outliers in the environment data when the agent experiences an outlier in its output. Through this method, the agent gradually completes its model and policy and performs well in more and more contexts. I also suggest that we may use the method to build a world model where the agent factorizes the objects in the world into features, abstract objects into comparable instances of concepts and map concepts to intents through features. I discuss the works needed to render the method practical, the connections to many fields in Artificial Intelligence and the broader implications of the method.
Figures & tables
figure 1: The problem: the agent needs to identify the data streams relevant for its intent
figure 2: Problem formulation. The agent observes the data stream X . It needs to identify the relevant ones Xr and define the relevant features Fr . It needs to learn the model y=y(u,Xr) and policy u=π(Xr,r) to satisfy the intent y=r .
figure 3: Context. Combinations of active and static data streams form contexts.
figure 4: The Example. The agent decides the number of servers u to control the response time y in a system. It has an intent to satisfy the requirement of the response time y=r . It observes a data stream X . It needs to identify the relevant ones Xr , define the relevant features Fr , and learn the model and policy.
figure 5: Data Stream X=(x0,x1,x2,x3) . Data stream x0 is generated by the arrival rate of packets. Data stream x1 is generated by the packet size. Data streams x2 and x3 are irrelevant. The initial context c0 is from time index 0 to 39. The new context c1 is from time index 40 to 79. Time indices from 80 to 99 have a mixture of contexts c0 and c1 for testing.
figure 6: Use the policy π0 in 3 time indices. The subplot “Data Stream” shows the data streams. The subplot “Control” shows the action u and the response time y achieved. The subplot “Learning” shows the model the agent thinks the sample belongs to and whether the agent performs learning.
figure 7: Detect new context. The new context arises at the start of time index 40. At first, the agent applies the policy π0 . It observes an outlier y=r in the intent outcome. It detects a new context from this outlier. It steps away from the model y0 and starts learning a new model and policy. Towards the end of time index 40, it satisfies the intent again. The same operation repeats in time index 41.
figure 8: Use updated model in 3 time indices. The values of x1 are different. The agent selects the model and applies the policy accordingly and observes that the intent is satisfied.
figure 9: Learning process. From the contexts, the agent identifies the relevant data streams Xr , defines the features Fr out of Xr and learns models y(u,Xr) and policies π(Xr,r) to satisfy its intent y=r . Through the features Fr , it abstracts individual objects into comparable instances of concepts.
figure 10: Learned knowledge. Concepts have features Fr . Features Fr generate data streams Xr . The model y(u,Xr) and policy π(Xr,r) are learned based on the data streams Xr to satisfy the intent y=r .
Dry road
Icy road
Flat road
X
X
Steep road
X
(?)
table 1: An example of combining features to better adapt to new contexts
figure 11: World Model. Features link concepts to intents.
figure 12: Use Spike-Timing-Dependent Plasticity. When the intent outcome has an outlier, the agent looks for outliers in the data streams. It links all the data streams that have outliers to a node and uses the node to represent the feature. It links the feature to the intent.