I understand that libraries can use a classification system like Dewey or LOC. Apparently, the decision as to how any particular book is classified, however, is made locally at each library. So this is my question: is there an agreed upon definition of the books that fit a particular classification? For example, I run a library. I just got a new book in. The book title is "Killing Others" and is nonfiction. The LOC number for murder is x. The Dewey number for homicide is y. I don't have time to read and analyze this or any other new book because there are just too many of them. Is there a definition, or a descriptive list of features and attributes of all books classified as y or x that I can consult? Like "books about murder have this and that, but if they also have this other thing, they should be classified under homicide"?