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Hi Sean,
In doing a quick check through some of the research published by ACM
(you may have done this already), it looks like a lot of the
experimental filesystems are using either a layered approach and/or
caches. Maybe the combination of a cache to allow for reverse reads of
bytes from blocks of data that were actually read sequentially based on
knowledge of the end of the file would help, but that's probably the
type of overhead you're trying to avoid.
However, if the assumption is that you want to do this for extremely
large chunks of XML--perhaps on a dedicated machine (implied for the
request for the filesystem solution), it's possible that the overhead
could be worth it.
ast
On Sat, 2006-04-01 at 08:22, Sean McGrath wrote:
> I have sketched out an algorithm for fast XML WF parsing utilising two
> threads that each start at opposite ends of the octet-stream and meet in
> the middle. The algorithm hinges on the fact that start- and end-tags
> are balanced. i.e. as one thread reads forward looking for foo
> start-tag, the other thread is reading backwards looking for foo end-tag.
>
> This also has the nice side effect of giving you accurate error messages
> quickly. i.e. as soon as a mismatched tag is found, it can be reported.
> This is particularly useful with recursive element types.
>
> Modern machines (even desktop boxes) will increasingly have multi-core
> CPUs as standard and I think it behooves us to find ways of exploiting
> that in the XML world.
>
> But to get the most out of the algorithm, you really need a filesystem
> that supports reading byte-streams backwards.
>
> Does anyone know of such a filesystem?
>
> thanks,
> Sean
>
>
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