Communication Ethics book part for Derivation Trees. (This is an automatically generated summary to avoid having huge posts on this page. Click through to read this post.)

As long as we consider only a single expression in isolation, there is no significant difference between software/documents and traditional expressions. Single, indivisible units are handled adequately by traditional copyright law; this should make sense, as this is a very common case in copyright law. Where things start getting complicated is when works start using other works to create our new work.

Under traditional copyright law and with traditional technology, the only way to use another work is to include some portion of the old work in some new work, either modified or not modified. Certain rules govern these uses if the original work is under copyright protection. There are endless details that have been worked out over the past few years, but it all basically boils down to the right to use the work and the right to pass that right on. The only possible way to use that work is to include a copy of it in the new work. That's the nature of conventional technology.

So let's look at a example. Consider a simple page in a magazine, with an advertisement using photos, a book review written by a free-lance author, a fair-use quote from the book, and the logo of the magazine. Look at a diagram of the important copyright relationships and agreements necessary for that page (below).The reason this works is that everything boils down to essentially one question: Does someone have the right to include a copy of some expression in some other expression, or not? There are a lot of details, like whether the permission can be passed on, whether the work can be modified, used only in part, or used only in certain geographical regions, but these are all variations on the same basic question of permission to include copies of expressions.

We can call the tree in the previous image the derivation tree of that expression. It shows what other expressions went into the creation of that expression, and the relationships between those expressions. Despite the fact that a derivation tree of many real-world expressions (such as a real magazine) grow immensely large they are manageable, because they are still quite straightforward.

An expression that does not have a derivation tree, because it is a fully original creation of some kind can be called an atomic expression. For instance, this paragraph considered as an expression on its own is an example of an atomic expression; all the words are fully my own, and as such I and I alone own full rights to it. An expression of some sort, such as a newspaper page or collage, that has some sort of derivation tree associated with it can be called a composite expression. Note that we're still examining the current expression doctrine, so it is still appropriate to use the term "expression". Perhaps someone has more established terms for these; I'd appreciate hearing about them.