Taru Karttunen wrote:
On Mon, 09 Jan 2012 08:01:27 -0500, Adam Chlipala<[email protected]>
wrote:
Does your library maintain the transactional abstraction? That is, if I
read a file twice within an Ur/Web page handler, and the file has been
modified from the outside between the first and second reads, will the
two blobs returned be different?
They will be different. I think that reading the file is like getting a
random number, something unknown will come out.
That's certainly a well-defined semantics. In some applications, one
might want to maintain invariants across the contents of files, so that
reading values x of file A and y of file B would always yield results
such that P(x, y), for some invariant P. You can't get that kind of
semantics if you don't do some explicit work to present consistent
snapshots of the full filesystem. (Personally, I'm very against
filesystems, period, which you can see reflected in the set of
operations in the Ur/Web standard library. :])
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