It is this recognition that allows us to formulate a rational and meaningful definition of the integrity of a human-perceived message, even in the light of infinite rendering variations.
- human-perceived message integrity
- When the message perceived by a human is composed of the same concrete parts, mixed as intended by the sender, the integrity is preserved. If parts have been added, removed, or modified, or rendering instructions have been added, removed, or modified, in ways not intended by the sender, then the message integrity is violated.
Again, we do not try to read the mind of the sender, but pay attention solely to the flow of concrete parts and their assembly. For instance, a novice web page creator may place an image tag in their HTML page and intend that every user see it. However, it is not this "intent" that is transmitted, instead it is an HTML image tag, <img src="/images/communicationEthics/something">. In HTML, the IMG tag does not truly mean "display this image", in the sense of an unbreakable contract. Instead, it is on the level of "strong suggestion to the browser", which it can take or leave as it wills, or as it is technically capable. Users may visit the web page with a graphical browser with image loading off, or with a text-only browser, or with an alternate-media browser with no visual component at all. All of these are acceptable under both the general understanding of the web, and even the technical specification of the HTML language:
The alt attribute specifies alternate text that is rendered when the image cannot be displayed (see below for information on how to specify alternate text ). User agents must render alternate text when they cannot support images, they cannot support a certain image type or when they are configured not to display images.
Emphasis mine.
In general, the actual message won't precisely match what the sender intends to convey, unless they are deliberately limiting their communication to the capabilities of whatever language they are using. In HTML, there isn't a way to say "The browser absolutely must display this image." The message can only match the sender's intent if the sender deliberately limits themselves to the limitations of HTML. The inability to truly express concepts completely correctly in any language is a deep philosophical problem, but such discussion does not gain us anything. The fact we can not narrowly and precisely define the intended "true message" does not mean that we must therefore deny it exists.
There is a lot of flexibility in how an HTML message is rendered. There is no flexibility in what set of concrete parts will go into a message. There is some set of images, text, applets, data, etc. that might be used to render the page, or might be elided by the browser. The set is finite and quite well defined with some simple analysis of the HTML page itself. Loading content from an additional source not described in an HTML page is a very distinct, identifiable event, and this constitutes an integrity breach.