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The corpus alone can't be sufficient. The corpus displays associations that are disproportionate for how we want to use it, because corpora are from the past. B
by rspeer 9y ago
The corpus alone can't be sufficient. The corpus displays associations that are disproportionate for how we want to use it, because corpora are from the past. But the point of ML is to build something that will be used in the future. [1]
There is no objective way to describe this difference between your training set and your test set, because you don't have data from the future. It requires a conscious decision. Enforcing that the future should be like the past is a conscious decision, and it's a lazy and unfortunate one.
This is just one instance of a problem that ML is already quite familiar with, and has been since "ML" was called "statistics": observed data produces a biased estimator of the actual distribution. You always have to correct your objectively-measured distributions for what you can't measure objectively. Here I mean "biased" in the mathematical sense; when it comes to human biases encoded in word embeddings, it also produces bias in the ethical sense. But there are many simpler instances of this.
For example: a maximum-likelihood language model assigns a probability of 0 to any word it has never seen. Maximum likelihood is, when measured, a better model of the input data than anything else. If you implement this completely objective language model, it would be useless when applied; it would output the impossible probability of 0 for most inputs. Instead you have to "smooth" and "correct" it for the fact that other words exist.
[1] https://twitter.com/random_walker/status/975700725807439879 https://twitter.com/random_walker/status/975700725807439879