Classification - comparison of one attribute to others attributes

Hi. I'm trying to classify authors of texts. I have 4 attributes containing the most commonly used words - attribute A B C and D. Attribute A is compared against A in rest of data, B against B in rest of data, etc.

But I want to check if attribute A exists in attributes A B C and D. For example:

1) row X has A with "example" value and B with "test" value

2) row Y  has A with "test" value and B with "qwerty" value

3) "test" value exists in both X and Y, so it should return true, so there is a bigger chance that author of X is the same as author of Y

How I can do that? I want to use it together with operators like Decision Tree, KNN, etc.