Re: Object tag crashes Internet Explorer 4.0

[djsd100 () cam ac uk (David Damerell)]

On Tue, 4 Aug 1998, Paul Leach (a Microsoftie) wrote:
> The possibility of infinite loops and infinite recursion in HTML has been
> discussed on the lists before. Trying to detect and prevent them is an
> instance of the "Turing machine halting" problem, and it is well known among
> computer scientists to be impossible.

This isn't even remotely true; and isn't made more valid by randomly
mentioning the Turing problem (something tells me our Mr. Leach is not
a computer scientist himself.) A fairly brute-force approach to their
detection would be simply to keep a count of how many times each
object had been displayed, and start throwing them away when it
exceeded some limit - quite high for, say, images, to allow for the
kind of pages with a red button on each bullet point (what I think of
this kind of HTML is another matter); quite low for pages of text or
framesets - also, establishing an separate upper limit on the overall
'depth' of a given page protects you against the hostile CGI script
that serves up the same thing with a million different names. There's
probably more sophisticated approaches based on graph theory, but I'm
not a mathematician any more.

--
David Damerell, Computer Officer, Department of Chemistry, Cambridge
Work: djsd100 () cam ac uk    Personal: damerell () chiark greenend org uk