URL now part of sequence!

[Frank Ellermann]

Meeussen Wouter (bkarnd) wrote:

> where does the *short* link http://purl.net/net/eisa/A057752"
> come from? what's 'purl.net'? is it a mirror? will it stay?

On the surface it's one of these "make a shorter link" features
like go.to, kickme.to, etc., working with redirections.

Will it stay (and stay free without ads) is the most important
question.  You may find an answer on their main page (use one
of http://purl.net/ http://purl.org/ http://purl.com/ or
http://purl.oclc.org/ ).  PURL is an acronym for "persistent
URL", they do expect to live longer than the target URL, and
then it would be easy to change the redirection(s) once, and
all links using the PURL would continue to work.

They started to implement it in 1995, maybe that answers your
"will it stay" question partially,  And OCLC (Online Computer
Library Center) is an organization of more than 40000 libraries
in more than 80 countries founded in 1967 - for the complete
article see http://www.oclc.org - they are serious about their
"persistence".

Anybody with an email address can register as a user and then
create PURLs starting with http://purl.net/net/etc (the other
domains purl.org, purl.com, and oclc.purl.org would also work).

It's not exactly what you want with GoogleBot, DMOZ, ZEAL (the
public directory of LookSmart), Yahoo!, etc., because AFAIK
they don't support redirected URLs - in the case of ZEAL I'm
sure.  But if you want a "persistent URL" for your homepage
independent of your current hoster, or even only a shorter URL,
then PURL could be a good idea.

They support complete and partial redirections.  A complete
redirection answers a HTTP GET /net/com/plete at purl.net with
a HTTP 302 Found and the target URL an.example/what/ever.html

http://purl.net/net/eisa is a complete redirection, the target
is http://www.research.att.com/~njas/sequences/index2_b.html -
at the moment, I changed this some time ago.

http://purl.net/net/eisa/ is a partial redirection.  Any HTTP
GET starting with net/eisa/ is answered with a HTTP 302 Found
and target (long line) ...

http://www.research.att.com/cgi-bin/access.cgi/as/njas/sequences/eisA.cgi?Anum=

...so if you asked for purl.net/net/eisa/oops this would result
in a lookup for Anum=oops and of course fail... ;-)  But Neil's
eisA.cgi is very tolerant, for A012345 you can do anything like
Anum=12345, Anum=012345, Anum=A12345, Anum=000012345, etc., and
if it works directly with eisA.cgi, then it also works after a
redirection.

Some things would not work, e.g. URLs with embedded blanks, or
"fragments" (URLs within a document, with a "#").  Changing
protocols on the fly (redirecting http;// to ftp;// or v.v.)
might also fail, I haven't tested this.  Some things I tried:

http://purl.net/net/scape/mocha
http://purl.net/net/scape/javascript
http://purl.net/net/scape/javascript/17+4
http://purl.net/net/scape/about
http://purl.net/net/scape/about/blank

etc.  The 17+4 really works with Netscape 3.x and enabled JS ;-)
My favourite in this series...

http://purl.net/net/scape/view-source

...has the same effect as view-source:about:global (this is all
Netscape 3.x stuff, especially mocha: and view-source: - but the
about: and javascript: tricks may work with other browserss too).

                          Bye, Frank

P.S.:  If some of the editors have or create a PURL account,
please inform me, I'd then add them to the net/eisa admin list.
Currently you shouldn't use net/eisa in any work designed to
live longer than I can manipulate a keyboard... ;-)