Classifying information by intention

When we say physics, chemistry, computer science, etc., we're classifying information by subjects. Subjects are one kind of distance metric used to relate facts, and usually determines if two facts belong to the same textbook. However, they're not the only way to classify information.

Another way is by intention. If you intend to publish a useful software, you need to know about programming languages, software design, UI/UX, product management, and marketing to varying degrees. You don't necessarily need to know everything about programming languages or software design.

Educational systems insist that even if you find a few facts about a subject useful, you still have to learn all the facts within the subject for the sake of completeness. Most of those facts won't even be useful.

Every fact might even be useful, to someone, but not necessarily to you. It's better to pick and choose and learn continuously, rather than gobbling up facts mindlessly.