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Re: http and ranges

From: David W. Morris <dwm@xpasc.com>
Date: Fri, 18 Sep 1998 15:58:12 -0700 (PDT)
To: Daniel Hellerstein <danielh@mailbox.econ.ag.gov>
Cc: http-wg@hplb.hpl.hp.com
Message-Id: <Pine.GSO.3.96.980918105834.6055D-100000@shell1.aimnet.com>
X-Mailing-List: <http-wg@cuckoo.hpl.hp.com> archive/latest/40

I think the trend in general is to move away from user entered URLs.

Another trend is away from complex GET URLs and toward use of POST as
well as either the Safe: approach or a new idempotent GETX method.

Also, adding new syntax to the URL has the possiblity of breaking
existing implementations because the parsing implementaton if often
flakey at best.

There is no reason that the future should be defined by the limitations
of current UIs and HTML attributes.

I believe the range: approach was orginally conceived to allow a PDF
viewer plugin to efficiently transfer portions of the file. Two other
uses were quickly identified ... recovery of a user interrupted
transfer ... quickly getting image meta data for layout purposes w/o
waiting for the full transfer. 

The whole range of ways and kinds of pieces users might want to 
request doesn't lend itself to user entry of byte level encoding.
There is no reason the current URL scheme can't retrieve whole documents
as well as pieces with simple URLs ... outside of the scope of HTTP
and URLs, the server implementation defines the interpretation of the
URL. With a SINGLE data file and/or DB, the URLs 
could all produce variant levels of zoom into the document. This can
be achieved today on some servers by creative use of mapping to cgi
programs. Or an imperceptable alteration of the URL to:
could be mapped to an ISAPI DLL on IIS, etc.

Also, thre are some pretty straight forward improvments to HTML and
UIs which would allow better access to the POST and possible GETX
methods.  Links which implement the POST method for example.

Dave Morris

On Fri, 18 Sep 1998, Daniel Hellerstein wrote:

> > Thanks. Now I see how to do a GET with range request.
> > Now, another question:
> > Is there a way to specify the offset or range with the http: URL
> > syntax ?
> > i.e. something like http://host/dir/file@range=0,500
> The real question is how such an addition (to some future http 1.2)
> would be used. I can think of two general cases:
> 1)Aas a means of obtaining a portion of a resource; such as a
> single chapter of a long document.
> But  one could always just have separate files containing chapter 1,
> chapter 2,.. ( as complements to the "entire document").  Alternatively,  a
> script (cgi-bin or whatever) that would parse the request line, looking
> for a "@range",  and (if found) use the "=0,500" to selectively return a
> portion of the document, should be fairly easy to create.
> 2) As a means of selectively updating a portion of an otherwise large
> resource. For example, acrobat can use a range: header to request
> selected pages of a long pdf file. 
> But this then means having client software (i.e.; browsers) that
> understand the request syntax being used.  But there already is a
> syntax that will support such actions (that is, the aforementioned use of
> range: request header).
> In other words, although new http methods, etc (such as  adoption of a
> RANGE  method) might be useful, I suspect it's not worth the trouble.
Received on Friday, 18 September 1998 16:19:10 UTC

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