Kolmogorov complexity

Kolmogorov complexity measures the randomness or unpredictability of a particular object.

Consider the following strings of 20 characters:

1. jkjkjkjkjkjkjkjkjkjk
2. asifnwöoxnfewäohawxr

The first string has lower complexity, as you could describe the string as "write jk 10 times", while the second string has no discernable pattern, so you could only describe it as "write asifnwöoxnfewäohawxr".

You could assess the originality or quality of information via this type of complexity. For example, the shorter the book summary, the worse the book. If you can cut down 99% of the length while still containing the same key information, that tells something about the quality of the book.

By contrast, the longer the book summary, the better the book, as it implies there are more unique ideas that are taken to a greater depth, warranting more time to explain them properly.

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