posted Jul 22, 2003
in Communication Ethics

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

Let's specify the derivation tree more precisely, so we can compare this to what happens in the software domain precisely.

An expression derivation tree is a standard tree structure. A tree structure connects nodes. Each node can have any number of children. A node can be a child of only one node. Each node has certain properties. The parent-child relationship (represented in a figure with a line connecting them) may also carry certain properties in the connection. For more complete information about tree structures, consult the web (or Wikipedia).

Trees are immensely useful structures, and are used in many different ways. In my derivation trees, all nodes represent some expression, perhaps some text, or a picture, or a movie. Each of these nodes has at least the following properties:

Along the links from children to parents multiple things flow:

It is easy to see with all of this how one can make a living just tracking and enforcing the relationships that arise in the copyright domain. The larger the composite work, the more sources for a work, the more complicated the story becomes.

(Mostly) Full derivation tree for Magazine Page

Note that even as verbose as this image is, and as oversimplified as the example is, even this isn't complete. For instance, does everyone have permission for the fonts used? How often do you think of that? In the real world, everything except maybe the stock photo and the quote would themselves break down into further composite expressions, but this should be enough to give you the idea.

Take a look at the Instructions for the Advertisement: Just because the advertisers bought space in the magazine to print their advertisement does not mean that the magazine can do whatever they like with the advertisement; they are obligated to do neither more nor less then what they agreed with the Advertiser. Also note that there are two instances where the owner of a composite expression, the Magazine Page and the Advertisement, where they also own one of the components. It's important to still show the sub-expressions, so one does not get the impression that the advertisement consists solely of a stock photo, which would be unlikely to be a compelling advertisement unless you got really lucky with someone's stock photo.

It is a common misconception that once you create an expression, you own full rights to that expression no matter what. In reality, what you own is certain rights to control how your work is used in other works. It is possible that someone else will completely independently come up with an effectively identical expression, and they will own full rights to it as well. It is recognized by the court system that fully independently coming up with the same expression is a very remote possibility, but it has happened before, especially in domains such as "musical melodies" where there are not necessarily a whole lot of distinct melodies to be copyrighted.

The derivation tree is just an equivalent way to represent the expression, one that highlights the complicated legal status of the expression; it is neither more nor less true, it's another view of the same thing.


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