The popular question
Regarding the `book`, `report`, and `article` document classes: what are the main differences?
collects many differences between the
article classes. In particular, some commands are not available in articles (like
\chapter) while others are not defined for books (like
What is the reason for these differences in functionality/availability of commands?
Some details: It is obvious that the current system has some disadvantages if one likes to switch from one classes to another one. For example, 'downgrading' a report with chapters to an article does not even compile and needs some manual work (or workaround). On the other hand, I can see that certain commands don't apply literally to all kinds of documents. In an article one would probably not speak of chapters or include back matters. Nonetheless, viewing the corresponding commands just as a way to structure the document does make sense. That is, there is no problem in regarding
\chapter as the highest level heading and
\front|main|backmatteras a way to tell latex 'now comes the following thing, so maybe change the formatting accordingly'. Of course the styling and effect of these commands have to be different in an article vs book.
So the refined question is: what is the advantage of the current classes versus a base class providing the same commands with an option for the style.