--------
Anselm Lingnau writes:
| John Chambers <[EMAIL PROTECTED]> writes:
|
| > There's no way to ask a
| > web server for a portion of a file; you just have to read through it
| > from the beginning.
|
| As a matter of fact you can ask a web server for a portion of a file,
| according to recent versions of HTTP (see RFC 2616, search for `range
| unit'). Of course the HTTP server needs to play along. Also it seems
| have to remember the exact position of each tune in the file, and if
| the file maintainer adds a few bytes at the beginning everything goes
| south until the next time your indexer looks at the file.
You're right. I looked at this a while back, and found that it was
essentially unusable. First, among the sites with ABC, I couldn't
find any web server other than the one here that actually implemented
this feature. And it's quite common for people to store ABC in large
multi-tune files. They don't always add tunes at the end; they are
more likely to use some logical or alphabetical order. New tunes are
inserted at the appropriate place in the file, and the tunes are
renumbered at random times. This is entirely reasonable, of course,
and it makes offsets unusable.
The general answer to this is XML, which allows you to label parts of
a file with meaningful names. It would be easy then for a client to
ask a server for a specific named portion of a file. But it's going
to be a while before we see XML used with ABC.
The ABC T and P header lines are an ABC-specific version of this, of
course. And we do have tools around that can extract sections using
these labels. But while this is a convenience for users, it still
means that the software must download the entire file until the
desired tune is found.
I'm getting tempted to do some prototyping of XML wrappers around ABC
on my site (in my copious spare time ;-). And we do have people who
object to downloading a portion of their files. Presumably they'd use
XML to just give a name to the entire file, making its contents a
single binary object that must be downloaded as in its entirety.
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