The diagram above shows a very broad viewpoint of learning theory.
| arrow | Typical statement | Examples |
| Past->Past | Some prediction algorithm A does almost as well as any of a set of algorithms. | Weighted Majority |
| Past->Future | Assuming independent samples, past performance predicts future performance. | PAC analysis, ERM analysis |
| Future->Future | Future prediction performance on subproblems implies future prediction performance using algorithm A. | ECOC, Probing |
A basic question is: Are there other varieties of statements of this type? Avrim noted that there are also “arrows between arrows”: generic methods for transforming between Past->Past statements and Past->Future statements. Are there others?