Rocky,
At first glance, you might conclude that predefined attributes should be read only. But this flexibility is a key advantage of AsciiDoc. I'll explain why.
AsciiDoc is all about keeping source and output/presentation separate. The predefined values carry with them a bias towards XML and XML-like output. It's these very attributes that need to be fined-tuned when creating other types of output, and one of the main reasons that they exist. In other words, they communicate an intent to create a glyph or series of characters without tying that content to a specific output format. That's exactly why they shouldn't be read only.
However, we can say that you shouldn't be overridding them unless you know what you are doing. Obviously, changing `amp` to resolve to `frogs` doesn't make a whole lot of sense...unless of course "frogs" represents "ampersand" in the output format you are targeting. That may seem strange, but consider that the value for trademark in a manpage is \(tm. Who knows what the output format requires.
Locked
