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: djsd100at_private Personal: damerellat_private
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