There is one more issue to resolve before considering this discussion complete, though, and that is the issue of delimiting messages. Consider the case where a person creates a web page and "intends" for it to be viewed in Netscape. Now consider two people visiting that page, one with Netscape and one with Internet Explorer. One sees the page as "intended", with the Netscape logo on the browser. Another sees it with the Internet Explorer logo. It seems that a part of the message has been "modified", yet intuitively we do not see this as an attack on integrity.
Suppose now we use a browser that adds the word "WRONG" in huge red type to every third web page. This does seem to be an attack on the message's integrity. Many debaters I've seen on the Internet happily munge these two together in their zeal to prove their point, but intuitively, there does seem to be a real difference. What is it?
The rather straightforward answer lies in the dependence of the messages.
- dependence
- Message A depends on Message B if a change in B significantly affects how A is perceived by the human.
There is some fuzziness in the word "significantly", but that is just the real world rearing its ugly head at us again. In the case of a browser, it may draw a title from the current web page and use it in its title bar, or as the title of the bookmarks, so technically what web page it is currently viewing does affect how the browser is perceived by the human, but these are really rather insignificant changes under any reasonable interpretation. Practically speaking, the browser, considered as a human-experienced message, is independent of the human-experienced message of the current web page. As evidence, consider the visual similarity between a browser showing an empty page, and one with an actual page. Flipping it around, it is possible for the web page to affect the browser in certain limited, well-documented manners (such as opening a new window without toolbars), but again it is not really a case of "the web page" manipulating the browser, it is a case of the browser doing its best to render the web page as the HTML suggests. The user can override those manipulations either with certain browser settings, or by using a browser that doesn't understand those concepts.
One frequent counterargument to earlier, cruder versions of this concept is that it would outlaw such things as a television, which always have the name of the television manufacturer on it, thus affecting all television programs viewed on the set. Of course this does not happen because the name is completely independent of what is on the television, persisting even when the device is completely unpowered. Similarly, on-screen menus overlayed on top of television programs are harmless, because they are also almost completely independent of the television program, with the possible exception of displaying basic information about what is currently being viewed, which has already been discussed.
This is the answer to the problem of how to delimit the interactions of messages. If two messages co-exist, and do not depend on each other in the sense given above, then neither violate the integrity of the other, no matter how they came to be co-existent. Dependence analysis thus degrades gracefully in the pre-smart message case, when messages could never react to each other and thus could not become dependent, and shows that no messages were ever dependent on another message, so this is indeed a new ethical problem, one almost completely misunderstood by most people at this time.