[userbinator]

I agree, this can be summarised as "abstraction hides bugs". I believe that although abstraction is a powerful tool, there is such a thing as too much of it, and when reading an XML document can cause access to other files, maybe even across the network, perhaps things have gone a little too far. This isn't like an obvious #include or @import, it's much more subtle.

When I first noticed that HTML doctypes have URLs in them, I inquisitively tried accessing them, and it brought up a lot of questions in my mind about why it was designed that way, what would happen if the URLs no longer existed, etc. Such an explicit external dependency just didn't feel right to me. Unfortunately most people either don't notice or seem to ignore these things...

Interestingly enough, not all XML parsers support external entities; the first one to come to mind is this: http://tibleiz.net/asm-xml/introduction.html

[justincormack]

They are supposed to be identifiers and not resolved. But using http for something not to be resolved is odd...