Internet-Draft                                                Ryan Moats
draft-ietf-urn-ietf-07.txt
draft-ietf-urn-ietf-08.txt                                          AT&T
Expires in six months                                       October                                      November 1998

                   A URN Namespace for IETF Documents
                  Filename: draft-ietf-urn-ietf-07.txt draft-ietf-urn-ietf-08.txt

Status of This Memo

      This document is an Internet-Draft. Internet-Draft and is in full conformance with
      all provisions of Section 10 of RFC2026.

      Internet-Drafts are working documents of the Internet Engineering
      Task Force (IETF), its areas, and its working groups.  Note that
      other groups may also distribute working documents as Internet-Drafts. Internet-
      Drafts.

      Internet-Drafts are draft documents valid for a maximum of six
      months and may be updated, replaced, or obsoleted by other
      documents at any time.  It is inappropriate to use Internet-
      Drafts as reference material or to cite them other than as ``work
      in progress.''

      The list of current Internet-Drafts can be accessed at
      http://www.ietf.org/ietf/1id-abstracts.txt

      The list of Internet-Draft Shadow Directories can be accessed at
      http://www.ietf.org/shadow.html.

      To learn the current status of any Internet-Draft, please check
      the ``1id-abstracts.txt'' listing contained in the Internet-
      Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net
      (Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East
      Coast), or ftp.isi.edu (US West Coast).

Abstract

   A system for Uniform Resource Names (URNs) must be capable of
   supporting new naming systems.  As an example of proposing a new
   namespace, this document proposes the 'ietf' "ietf" namespace.  This
   namespace consists of the RFC family of documents (RFCs, STDs, FYIs,
   and BCPs) developed by the IETF and published by the RFC Editor, the
   minutes of working groups (WG) and birds of a feather (BOF) meetings
   that occur during IETF conferences, and the Internet Drafts published
   by the Internet Drafts Editor.  Both the current URN framework and
   URN syntax support this namespace.

0.1 Changes from -02

   This document has been restructured to use the template proposed in
   draft-ietf-urn-nid-req-03.txt.  Example Perl scripts for resolving
   this namespace have been supplied in an Appendix.

0.2 Changes from -03

   Text was added to the template clarifying persistence and uniqueness.
   Support for the BCP document series added to the examples and the
   ABNF.

0.3 Changes from -04

   More clarifications for the persistence section.  In addition,
   cleaned up some typos and ensured that the Appendix examples are
   functional

0.4 Changes from -05

   Based on a number of requests, i-ds have been added to the structure
   and resolvers. In addition, some examples have been added.

0.4 Changes from -06

   Some changes of the template to conform with draft-ietf-urn-nid-req-
   06.txt.  Minor editing of some of the sections for more clarity.

1. Introduction

   This document proposes the "ietf" namespace, which consists of the
   RFC family of documents (RFCs, STDs, FYIs, and BCPs) developed by the
   IETF and published by the RFC editor and the minutes of working
   groups (WG) and birds of a feather (BOF) meetings that occur during
   IETF conferences.

   The namespace specification is for a formal namespace.

2. Specification Template

        Namespace ID:

                "ietf" requested.

        Registration Information:

                Registration version number: 1
                Registration date: 1998-10-09 1999-04-22

        Declared registrant of the namespace:

                Ryan Moats
                jayhawk@att.com
                AT&T
                15621 Drexel Circle
                Omaha, NE 68135-2358

        Declaration of structure:

                The identifier has the following ABNF [2] specification:

                NSS = (family ":" number) / ("mtg-" number "-" wgbofname)
                      ( "id:" name)
                family = "rfc" / "std" / "fyi" / "bcp"
                number = 1*DIGIT
                wgbofname = 1*LETDIGIT 1*(DIGIT/ALPHA)
                name           =  id draft name beginning with "draft-" and trailing
                        type removed (e.g. ietf-urn-ietf-06)
                LETDIGIT draft-name "-" draft-version

                draft-name     = DIGIT draft-ietf / %x41-%x5a draft-individual / %x61-%x7a
                DIGIT draft-rfced
                draft-ietf     = "ietf-" wgbofname "-" draft-title
                draft-individual = draft-author "-" draft-title
                draft-rfced     = "rfced-" draft-title
                draft-title    = draft-namepart *( "-" draft-namepart )

                draft-author   = 1*(DIGIT/ALPHA)
                draft-nameart  = 1*(DIGIT/ALPHA)
                wgbofname      = %x30-%x39 1*(DIGIT/ALPHA)
                number         = 1*DIGIT
                draft-version  = 2*DIGIT

                If the IESG (or it successor) adds a new document
                series, this ABNF specification will need to be
                updated.  Further, if a working group or BOF is
                created that used characters outside the range of this
                ABNF specification, this specification will need to be
                updated.  Any system intended to resolve names for
                this namespace should be written with the awareness
                that this could occur at any time.

        Relevant ancillary documentation:

                The intended RFC document is currently
draft-ietf-urn-ietf-08.

        Identifier uniqueness considerations:

                Because the rfc-editor assigns the RFC number uniquely
                these URNs are unique.  Since the mapping between RFCs
                and other rfc-editor document series (STDs, FYIs or
                BCPs) is not necessarily one-to-one, uniqueness of
                STDs, FYIs and BCPs are defined based on the document
                mappings maintained by the RFC Editor (the index files
                "rfc-index.txt", "fyi-index.txt", "bcp-index.txt",
                "std-index.txt") are defined to be the definitive
                statement of the assignment of RFC Family URNs in this
                namespace.  The meeting minutes portion of the
                namespace is guaranteed unique because the URN
                includes the sequence number of the IETF conference.
                The document mapping maintained by the Internet Drafts
                editor ("1id-abstracts.txt") is defined as the
                definitive statement of the assignment of URNs for
                the internet draft portion of this namespace.

        Identifier persistence considerations:

                Persistence of the URNs of this namespace is
                independent of the mutability of the underlying
                documents.  A URN once assigned will never be
                reassigned to a different resource; the assignment is
                persistent and immutable.  Distinct from this, the
                resources identified as RFCs are immutable, whereas
                the other sorts of documents, STDs, FYIs, and BCPs are
                not.  They may be composites of one or more RFCs and
                the set of RFCs that includes them may change with
                time.  It is important to note that this mutability of
                some resources is independent of the immutability of
                URN assignment to a resource.

        Process of identifier assignment:

                Assignment of URNs from this namespace occurs in three
                ways.  The first is through publication of a new RFC,
                FYI, STD or BCP is by the RFC Editor. This new document
                will have a new series number and will therefore define
                a new URN.  The document mappings maintained by the
                RFC Editor (the index files "rfc-index.txt",
                "fyi-index.txt", "bcp-index.txt" and "std-index.txt")
                are defined to be the definitive statement of the
                assignment of RFC Family URNs in this namespace.

                The second way a URN is assigned is through the filing
                of meeting minutes by a working group or birds of a
                feather as part of an IETF conference.  The list of
                minutes maintained by the IETF for each working group
                and conference in the subtree pointed at by the URL
                ftp://ietf.org/ietf/ is considered the definitive
                assignment of URNs for working group or birds of a
                feather minutes.

                The third way a URN is assigned is through the
                publication of a new internet-draft by the Internet
                Draft Editor.  This draft will have a distinct name
                (and version number) and therefore defined a new URN.
                The document mapping maintained by the Internet Drafts
                editor ("1id-abstracts.txt") is defined as the
                definitive statement of the assignment of URNs for
                this portion of the namespace.

        Process of identifier resolution:

                A mirrored copy of the underlying documentation is
                required to resolve these URNs.  Resolution via
                HTTP is done by a set of simple Perl cgi-bin
                scripts presented in Appendix A.

        Rules for Lexical Equivalence:

                The entire URN is case-insensitive.

        Conformance with URN Syntax:

                There are no additional characters reserved.

        Validation mechanism:

                None specified. additional to resolution specified

        Scope:

                Global.

3. Examples

   The following are examples of URNs that a resolver for this namespace
   can resolve:

           urn:ietf:rfc:2141
           urn:ietf:std:50
           urn:ietf:id:ietf-urn-ietf-06.txt
           urn:ietf:id:ietf-urn-ietf-06
           urn:ietf:mtg-41-urn

4. Security Considerations

   Because this namespace defines no additional reserved characters, it
   does not add any security considerations beyond those inherent from
   the existence of the reserved characters from [1].  Further, none of
   the reserved characters from [1] are used in the definition of the
   NSS. This means that resolvers for this namespace may be considered
   "secure" in the sense that any escaping of characters in the NSS MUST
   result in the resolver indicating that the URN has incorrect syntax.

5. Acknowledgments

   Thanks to various members of the URN working group for comments on
   earlier drafts of this document.  The work described in this document
   is partially supported by the National Science Foundation,
   Cooperative Agreement NCR-9218179.

6. References

   Request For Comments (RFC) and Internet Draft documents are available
   from <URL:ftp://ftp.internic.net> and numerous mirror sites.

         [1]         R. Moats, "URN Syntax," RFC 2141, May 5, 1997.

         [2]         D. Crocker, P. Overell, "Augmented BNF for Syntax
                     Specifications: ABNF," RFC 2234, November 1997.

7. Author's Address

   Ryan Moats
   AT&T
   15621 Drexel Circle
   Omaha, NE 68135-2358
   USA

   Phone:  +1 402 894-9456
   EMail:  jayhawk@att.com

Appendix A.  Example Resolution Scripts

   The following scripts are examples that can be used for resolving
   URNs in this namespace.

A.1 I2C

#!/usr/local/bin/perl

use strict;

#
# this is a URN 2 URC resolver for the ietf namespace
#

my(%cite) = (
  bcp => "/ftp/rfc/bcp-index.txt",
  fyi => "/ftp/fyi/fyi-index.txt",
  id => "/ftp/internet-drafts/1id-abstracts.txt",
  rfc => "/ftp/rfc/rfc-index.txt",
  std => "/ftp/std/std-index.txt"
);
my(%number2date) = (
  44 => "99mar",
  43 => "98dec", 42 => "98aug", 41 => "98apr",
  40 => "97dec", 39 => "97aug", 38 => "97apr",
  37 => "96dec", 36 => "96jun", 35 => "96mar",
  34 => "95dec", 33 => "95jul", 32 => "95apr",
  31 => "94dec", 30 => "94jul", 29 => "94mar",
  28 => "93nov", 27 => "93jul", 26 => "93mar",
  25 => "92nov", 24 => "92jul", 23 => "92mar",
  22 => "91nov", 21 => "91jul", 20 => "91mar",
  19 => "90dec" );

my($wgpath) = "/ftp/ietf";
my($urn) = $ENV{'QUERY_STRING'};
my($host) = $ENV{'SERVER_NAME'}; #get my host name for ftp: URLs
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

(&resolveid($1), exit) if ($urn =~ /urn:ietf:id:(i); /urn:ietf:id:(\S+)/i);
(&resolverfc($1, $2), exit) if ($urn =~ /urn:ietf:(72)/i); /urn:ietf:(\w*):(\d*)/i);
(&resolvemtg($1, $2), exit) if ($urn =~ /urn:ietf:mtg-(9*)-(
120&urn_error("400 /urn:ietf:mtg-(\d*)-(\w*)/i);
&urn_error("400 Bad Request0); Request\n");

sub resolvemtg {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found0) Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
    print "Status:  200 OK70; OK\r\n";
    print "Content-type: text/html70; text/html\r\n\r\n";
    print "<HTML>0TITLE>Citation "<HTML>\n<TITLE>Citation for $urn</TITLE>0; $urn</TITLE>\n";
    print "<BODY>0; "<BODY>\n";
    print "<H1><A HREF= HREF=\"$link\">$urn</A>:</H1>\n";
    print "Minutes of the $sesnam working group from the " . &end($ietfnum)
. " IETF";
    print "</BODY>0/HTML>0; "</BODY>\n</HTML>\n";
    return;
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
    print "Status:  200 OK70; OK\r\n";
    print "Content-type: text/html70; text/html\r\n\r\n";
    print "<HTML>0TITLE>Citation "<HTML>\n<TITLE>Citation for $urn</TITLE>0; $urn</TITLE>\n";
    print "<BODY>0; "<BODY>\n";
    print "<H1><A HREF= HREF=\"$link\">$urn</A>:</H1>\n";
    print "Minutes of the $sesnam working group from the " . &end($ietfnum)
. " IETF";
    print "</BODY>0/HTML>0; "</BODY>\n</HTML>\n";
    return;
  }
  &urn_error("404 Not Found0); Found\n");
}

sub end {
  my($inarg)=@_;
  return $inarg . "st" if ($inarg =~ /1$/);
  return $inarg . "nd" if ($inarg =~ /2$/);
  return $inarg . "rd" if ($inarg =~ /3$/);
  return $inarg . "th";
}

sub resolverfc {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme, $value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  if (!defined $cite{$scheme}) {
    &urn_error("404 Not Found0); Found\n");
  }

  $flag = 0;
  open(INPUT, "$cite{$scheme}");
  while (<INPUT>) {
    $flag = 1 if (/^0*$value /);
    if ($flag == 1) {
      last if (/^$/);
      chop;
      push @bib,$_;
    }
  }

  if ($scheme ne "rfc") {
    print "Status:  200 OK70; OK\r\n";
    print "Content-type: text/html70; text/html\r\n\r\n";
    $bib[0] =~ s/^[0-9]*/<B>/; s/^[0-9]*\s*/<B>/;
    for ($i=0; $i<=$#bib; $i+=1) {
      last if ($bib[$i] =~ s/./.</B>/); s/\./.<\/B>/);
    }
    for ($i=0;$i<=$#bib;$i+=1) {
      $k=$bib[$i];
      while ($k =~ /(fyi|std|rfc|bcp)([0-9]+)(.*)/i) {
        push @ref,"$1$2";
        $k=$3;
      }
      $done="";
      foreach $j (@ref) {
        next if ($done =~ $j);
        $done .= "$j ";
        $l = $j;
        $l =~ tr/A-Z/a-z/;
        $link=&make_link("$l");
        $bib[$i] =~ s/$j/<A HREF="$link">$j</A>/g; HREF="$link">$j<\/A>/g;
      }
    }
    print "<HTML>0TITLE>Citation "<HTML>\n<TITLE>Citation for $urn</TITLE>0; $urn</TITLE>\n";
    print "<BODY>0; "<BODY>\n";
    $link=&make_link("$scheme$value");
    print "<H1><A HREF= HREF=\"$link\">$scheme$value</A>:</H1>\n";
    foreach $i (@bib) {
      print "$i0; "$i\n";
    }
    print "</BODY>0/HTML>0; "</BODY>\n</HTML>\n";
  } else {
    print "Status:  200 OK70; OK\r\n";
    print "Content-type: text/html70; text/html\r\n\r\n";
    $bib[0] =~ s/^[0-9]*//; s/^[0-9]*\s*//;
    $j=0;
    for ($i=0; $i<=$#bib; $i+=1) {
      $j += ($bib[$i] =~ s/, "/, <B>"/);
      $j += ($bib[$i] =~ s/",/"</B>,/); s/",/"<\/B>,/);
    }
    for ($i=0;$i<=$#bib;$i+=1) {
      $k=$bib[$i];
      while ($k =~ /(fyistdrfc|bcp)([0-9]+)(.*)/i) /(fyi\s|std\s|rfc|bcp)([0-9]+)(.*)/i) {
        push @ref,"$1$2";
        $k=$3;
      }
      $done="";
      foreach $j (@ref) {
        next if ($done =~ $j);
        $done .= "$j ";
        $l = $j;
        $l =~ s//g; s/\s//g;
        $l =~ tr/A-Z/a-z/;
        $link=&make_link("$l");
        $bib[$i] =~ s/$j/<A HREF="$link">$j</A>/g; HREF="$link">$j<\/A>/g;
      }
    }
    print "<HTML>0TITLE>Citation "<HTML>\n<TITLE>Citation for $urn</TITLE>0; $urn</TITLE>\n";
    print "<BODY>0; "<BODY>\n";
    $link=&make_link("$scheme$value");
    print "<H1><A HREF= HREF=\"$link\">$scheme$value</A>:</H1>\n";
    foreach $i (@bib) {
      print "$i0; "$i\n";
    }
    print "</BODY>0/HTML>0; "</BODY>\n</HTML>\n";
  }
}

sub make_link {
  my($sc);
  my($inarg)=@_;
  ($sc=$1) if ($inarg =~ /([a-z]*)/);
  return "/$sc/$inarg.ps" if (-e "/ftp/$sc/$inarg.ps");
  return "/$sc/$inarg.html" if (-e "/ftp/$sc/$inarg.html");
  return "/$sc/$inarg.txt";
}

sub urn_error {
  my($code) = @_; #store failure code here...

  print "Status:  $code";
  print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2C $code</title></head>0; $code</title></head>\n";
  print "<BODY>0; "<BODY>\n";
  print "<h1>URN to URC resolution failed for the URN:</h1>0; URN:</h1>\n";
  print "<hr><h3>$urn</h3>0; "<hr><h3>$urn</h3>\n";
  print "</body>0; "</body>\n";
  print "</html>0; "</html>\n";
  exit;

};

sub resolveid {
  my($flag,@bib,$i,$k,$j,$count,@ref);
  my($l,$link, $hdr, $done);
  my($value) = @_;
  my($scheme) = "id";

  open(INPUT, "$cite{$scheme}");
  while (<INPUT>) {
#
# capture record
#
    if ($flag == 1 || /^ /^\s+\"/) {
      push @bib,$_;
      ($hdr = -1, $count = 0, $flag = 1) if (/^ (/^\s+\"/);
      $count++ if (/^/); (/^\s+$/);
    }
    if ($count == 1) {
      $hdr = $#bib if ($hdr == -1);
    }
    if ($count == 2) {
      for ($i=0; $i<=$hdr; $i+=1) {
            if ($bib[$i] =~ /<(.*)>/) {
              $l = $1;
              if ($l eq "draft-$value.txt" || $l eq "draft-$value.ps") {
                print "Status:  200 OK70; OK\r\n";
                print "Content-type: text/html70; text/html\r\n\r\n";
                print "<HTML>0TITLE>Citation "<HTML>\n<TITLE>Citation for $urn</TITLE>0; $urn</TITLE>\n";
                print "<BODY>0; "<BODY>\n";
                print "<a href=
href=\"http://blackhole.vip.att.net/internet-drafts/$l\">$l</a>:\n";
                print "<pre>0; "<pre>\n";
                foreach $i (@bib) {
                  print "$i";
                }
                print "</pre>0; "</pre>\n";
                print "</BODY>0/HTML>0; "</BODY>\n</HTML>\n";
                exit;
              }
            }
      }
      $flag = 0;
      @bib = ();
    }
  }
  &urn_error("404 Not Found0); Found\n");
}

A.2 I2L

#!/usr/local/bin/perl

use strict;

#
# this is a URN 2 URL resolver for the ietf namespace
#

my(%pathbase) = (
  rfc => "rfc/rfc",
  fyi => "fyi/fyi",
  std => "std/std",
  bcp => "bcp/bcp",
  id => "internet-drafts/draft-", "internet-drafts/draft-"
);

my(%number2date) = (
  44 => "99mar",
  43 => "98dec", 42 => "98aug", 41 => "98apr",
  40 => "97dec", 39 => "97aug", 38 => "97apr",
  37 => "96dec", 36 => "96jun", 35 => "96mar",
  34 => "95dec", 33 => "95jul", 32 => "95apr",
  31 => "94dec", 30 => "94jul", 29 => "94mar",
  28 => "93nov", 27 => "93jul", 26 => "93mar",
  25 => "92nov", 24 => "92jul", 23 => "92mar",
  22 => "91nov", 21 => "91jul", 20 => "91mar",
  19 => "90dec" );

my($wgpath) = "/ftp/ietf";
my($urn) = $ENV{'QUERY_STRING'};
my($host) = $ENV{'SERVER_NAME'}; #get my host name for ftp: URLs
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

(&resolveid($1), exit) if ($urn =~ /urn:ietf:id:(i); /urn:ietf:id:(\S+)/i);
(&resolverfc($1, $2), exit) if ($urn =~ /urn:ietf:(72)/i); /urn:ietf:(\w*):(\d*)/i);
(&resolvemtg($1, $2), exit) if ($urn =~ /urn:ietf:mtg-(9*)-(

120&urn_error("400 /urn:ietf:mtg-(\d*)-(\w*)/i);
&urn_error("400 Bad Request0); Request\n");

sub resolvemtg {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found0) Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
    print "Status:  302 Moved temporarily0; temporarily\n";
    print "Location: $link0; $link\n";
    return;
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
    print "Status:  302 Moved temporarily0; temporarily\n";
    print "Location: $link0; $link\n";
    return;
  }
  &urn_error("404 Not Found0); Found\n");
}

sub end {
  my($inarg)=@_;
  return $inarg . "st" if ($inarg =~ /1$/);
  return $inarg . "nd" if ($inarg =~ /2$/);
  return $inarg . "rd" if ($inarg =~ /3$/);
  return $inarg . "th";
}

sub resolverfc {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme, $value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($txttry)="/ftp/$pathbase{$scheme}$value.txt";
  my($pstry)="/ftp/$pathbase{$scheme}$value.ps";
  my($htmltry)="/ftp/$pathbase{$scheme}$value.html";
MIME_SWITCH: {
    if ($accept =~ /application/postscript/ /application\/postscript/ && -f $pstry) {
      print "Status:  302 Moved temporarily0; temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.ps0; http://$host/$pathbase{$scheme}$value.ps\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /text/html/ /text\/html/ && -f $htmltry) {
      print "Status:  302 Moved temporarily0; temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.html0; http://$host/$pathbase{$scheme}$value.html\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /text/plain/ /\*\/\*|text\/plain/ && -f $txttry) {
      print "Status:  302 Moved temporarily0; temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.txt0; http://$host/$pathbase{$scheme}$value.txt\n\n";
      last MIME_SWITCH;
    }
    &urn_error("404 Not Found0); Found\n");
  }
}

sub urn_error {
  my($code) = @_; #store failure code here...

  print "Status:  $code";
  print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2L $code</title></head>0; $code</title></head>\n";
  print "<BODY>0; "<BODY>\n";
  print "<h1>URN to URL resolution failed for the URN:</h1>0; URN:</h1>\n";
  print "<hr><h3>$urn</h3>0; "<hr><h3>$urn</h3>\n";
  print "</body>0; "</body>\n";
  print "</html>0; "</html>\n";
  exit;
}

sub resolveid {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme) = "id";
  my($value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($txttry)="/ftp/$pathbase{$scheme}$value.txt";
  my($pstry)="/ftp/$pathbase{$scheme}$value.ps";
  my($htmltry)="/ftp/$pathbase{$scheme}$value.html";
MIME_SWITCH: {
    if ($accept =~ /application/postscript/ /application\/postscript/ && -f $pstry) {
      print "Status:  302 Moved temporarily0; temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.ps0; http://$host/$pathbase{$scheme}$value.ps\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /text/html/ /text\/html/ && -f $htmltry) {
      print "Status:  302 Moved temporarily0; temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.html0; http://$host/$pathbase{$scheme}$value.html\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /text/plain/ /\*\/\*|text\/plain/ && -f $txttry) {
      print "Status:  302 Moved temporarily0; temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.txt0; http://$host/$pathbase{$scheme}$value.txt\n\n";
      last MIME_SWITCH;
    }
    &urn_error("404 Not Found0); Found\n");
  }
}

A.3 I2Ls

#!/usr/local/bin/perl

use strict;

#
# this is a URN 2 URLs resolver for the ietf namespace
#

my(@urls);

my(%pathbase) = (
  rfc => "rfc/rfc",
  fyi => "fyi/fyi",
  std => "std/std",
  bcp => "bcp/bcp",
  id => "internet-drafts/draft-"
);

my(%number2date) = (
  44 => "99mar",
  43 => "98dec", 42 => "98aug", 41 => "98apr",
  40 => "97dec", 39 => "97aug", 38 => "97apr",
  37 => "96dec", 36 => "96jun", 35 => "96mar",
  34 => "95dec", 33 => "95jul", 32 => "95apr",
  31 => "94dec", 30 => "94jul", 29 => "94mar",
  28 => "93nov", 27 => "93jul", 26 => "93mar",
  25 => "92nov", 24 => "92jul", 23 => "92mar",
  22 => "91nov", 21 => "91jul", 20 => "91mar",
  19 => "90dec" );

my($wgpath) = "/ftp/ietf";
my($urn) = $ENV{'QUERY_STRING'};
my($host) = $ENV{'SERVER_NAME'}; #get my host name for ftp: URLs
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

(&resolveid($1), exit) if ($urn =~ /urn:ietf:id:(i); /urn:ietf:id:(\S+)/i);
(&resolve1($1, $2), exit) if ($urn =~ /urn:ietf:(72)/i); /urn:ietf:(\w*):(\d*)/i);
(&resolve2($1, $2), exit) if ($urn =~ /urn:ietf:mtg-(9*)-(
120&urn_error("400 /urn:ietf:mtg-(\d*)-(\w*)/i);
&urn_error("400 Bad Request0); Request\n");

sub resolve2 {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found0) Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
    $link=~s/^/ftp///;
    $link=~s/^\/ftp\///;
    my($ftplink)="ftp://$host/$link";
    my($httplink)="http://$host/$link";
    my($glink)="gopher://$host:70/0/$link";
    if ($accept =~ /text/uri-list/) /text\/uri-list/) { #look for text/uri-list, otherwise
text/html
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/uri-list0; text/uri-list\n\n\n";
      print "#$urn0; "#$urn\n";
      print "$ftplink0; "$ftplink\n";
      print "$httplink0; "$httplink\n";
      print "$glink0; "$glink\n";
    }
    if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ls</title></head>0; I2Ls</title></head>\n";
      print "<BODY>0; "<BODY>\n";
      print "<h1>URN $urn resolves to the following URLs:</h1>0; URLs:</h1>\n";
      print "<hr><ul>0; "<hr><ul>\n";
      print "<a href= href=\"$ftplink\">$ftplink</a>\n";
      print "<a href= href=\"$httplink\">$httplink</a>\n";
      print "<a href= href=\"$glink\">$glink</a>\n";
      print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
    }
    return;
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
    $link=~s/^/ftp///;
    $link=~s/^\/ftp\///;
    my($ftplink)="ftp://$host/$link";
    my($httplink)="http://$host/$link";
    my($glink)="gopher://$host:70/0/$link";
    if ($accept =~ /text/uri-list/) /text\/uri-list/) { #look for text/uri-list, otherwise
text/html
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/uri-list0; text/uri-list\n\n\n";
      print "#$urn0; "#$urn\n";
      print "$ftplink0; "$ftplink\n";
      print "$httplink0; "$httplink\n";
      print "$glink0; "$glink\n";
    }
    if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ls</title></head>0; I2Ls</title></head>\n";
      print "<BODY>0; "<BODY>\n";
      print "<h1>URN $urn resolves to the following URLs:</h1>0; URLs:</h1>\n";
      print "<hr><ul>0; "<hr><ul>\n";
      print "<a href= href=\"$ftplink\">$ftplink</a>\n";
      print "<a href= href=\"$httplink\">$httplink</a>\n";
      print "<a href= href=\"$glink\">$glink</a>\n";
      print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
    }
    return;
  }
  &urn_error("404 Not Found0); Found\n");
}

sub resolve1 {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme, $value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($try)="/ftp/$pathbase{$scheme}$value.txt";
  if (-f $try) {
    push(@urls, "http://$host/$pathbase{$scheme}$value.txt");
    push(@urls, "ftp://$host/$pathbase{$scheme}$value.txt");
    push(@urls, "gopher://$host:70/0/$pathbase{$scheme}$value.txt");
  }
  $try="/ftp/$pathbase{$scheme}$value.ps";
  if (-f $try) {
    push(@urls, "http://$host/$pathbase{$scheme}$value.ps");
    push(@urls, "ftp://$host/$pathbase{$scheme}$value.ps");
    push(@urls, "gopher://$host:70/0/$pathbase{$scheme}$value.ps");
  }
  $try="/ftp/$pathbase{$scheme}$value.html";
  if (-f $try) {
    push(@urls, "http://$host/$pathbase{$scheme}$value.html");
    push(@urls, "ftp://$host/$pathbase{$scheme}$value.html");
  }

  &urn_error("404 Not Found0) Found\n") if ($#urls == -1);

MIME_SWITCH: {
    if ($accept =~ /text/uri-list/) /text\/uri-list/) { #look for text/uri-list, otherwise
text/html
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/uri-list0; text/uri-list\n\n\n";
      print "#$urn0; "#$urn\n";
      foreach $i (@urls) {
        print "$i0; "$i\n";
      }
      last MIME_SWITCH;
    }
    if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ls</title></head>0; I2Ls</title></head>\n";
      print "<BODY>0; "<BODY>\n";
      print "<h1>URN $urn resolves to the following URLs:</h1>0; URLs:</h1>\n";
      print "<hr><ul>0; "<hr><ul>\n";
      foreach $i (@urls) {
        print "<LI><A HREF= HREF=\"$i\">$i</A>\n";
      }
      print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
      last MIME_SWITCH;
    }
  }
}

sub urn_error {
  my($code) = @_; #store failure code here...

  print "Status: $code";
  print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2L $code</title></head>0; $code</title></head>\n";
  print "<BODY>0; "<BODY>\n";
  print "<h1>URN to URL resolution failed for the URN:</h1>0; URN:</h1>\n";
  print "<hr><h3>$urn</h3>0; "<hr><h3>$urn</h3>\n";
  print "</body>0; "</body>\n";
  print "</html>0; "</html>\n";
  exit;
}

sub resolveid {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($value) = @_;
  my($scheme) = "id";
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($try)="/ftp/$pathbase{$scheme}$value.txt";
  if (-f $try) {
    push(@urls, "http://$host/$pathbase{$scheme}$value.txt");
    push(@urls, "ftp://$host/$pathbase{$scheme}$value.txt");
    push(@urls, "gopher://$host:70/0/$pathbase{$scheme}$value.txt");
  }
  $try="/ftp/$pathbase{$scheme}$value.ps";
  if (-f $try) {
    push(@urls, "http://$host/$pathbase{$scheme}$value.ps");
    push(@urls, "ftp://$host/$pathbase{$scheme}$value.ps");
    push(@urls, "gopher://$host:70/0/$pathbase{$scheme}$value.ps");
  }
  $try="/ftp/$pathbase{$scheme}$value.html";
  if (-f $try) {
    push(@urls, "http://$host/$pathbase{$scheme}$value.html");
    push(@urls, "ftp://$host/$pathbase{$scheme}$value.html");
  }
  &urn_error("404 Not Found0) Found\n") if ($#urls == -1);

MIME_SWITCH: {
    if ($accept =~ /text/uri-list/) /text\/uri-list/) { #look for text/uri-list, otherwise
text/html
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/uri-list0; text/uri-list\n\n\n";
      print "#$urn0; "#$urn\n";
      foreach $i (@urls) {
        print "$i0; "$i\n";
      }
      last MIME_SWITCH;
    }
    if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ls</title></head>0; I2Ls</title></head>\n";
      print "<BODY>0; "<BODY>\n";
      print "<h1>URN $urn resolves to the following URLs:</h1>0; URLs:</h1>\n";
      print "<hr><ul>0; "<hr><ul>\n";
      foreach $i (@urls) {
        print "<LI><A HREF= HREF=\"$i\">$i</A>\n";
      }
      print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
      last MIME_SWITCH;
    }
  }
}

A.4 I2Ns

#!/usr/local/bin/perl

use strict;

#
# this is a URN 2 URNs resolver for the ietf namespace
#

my(%cite) = (
  rfc => "/ftp/rfc/rfc-index.txt",
  fyi => "/ftp/fyi/fyi-index.txt",
  std => "/ftp/std/std-index.txt",
  bcp => "/ftp/rfc/bcp-index.txt"
);

my(%number2date) = (
  44 => "99mar",
  43 => "98dec", 42 => "98aug", 41 => "98apr",
  40 => "97dec", 39 => "97aug", 38 => "97apr",
  37 => "96dec", 36 => "96jun", 35 => "96mar",
  34 => "95dec", 33 => "95jul", 32 => "95apr",
  31 => "94dec", 30 => "94jul", 29 => "94mar",
  28 => "93nov", 27 => "93jul", 26 => "93mar",
  25 => "92nov", 24 => "92jul", 23 => "92mar",
  22 => "91nov", 21 => "91jul", 20 => "91mar",
  19 => "90dec" );

my($wgpath) = "/ftp/ietf";
my($urn) = $ENV{'QUERY_STRING'};
my($host) = $ENV{'SERVER_NAME'}; #get my host name for ftp: URLs
my($port) = $ENV{'SERVER_PORT'}; $ENV={'SERVER_PORT'};
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

(&resolve1("id", $1), exit) if ($urn =~ /urn:ietf:id:(/i);

(&resolve1($1, $2), exit) if ($urn =~ /urn:ietf:(72)/i); /urn:ietf:(\w*):(\d*)/i);
(&resolve2($1, $2), exit) if ($urn =~ /urn:ietf:mtg-(9*)-(
120&urn_error("400 /urn:ietf:mtg-(\d*)-(\w*)/i);
&urn_error("400 Bad Request0); Request\n");

sub resolve2 {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found0) Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
    if ($accept =~ /text/uri-list/) /text\/uri-list/) {
        print "Status: 200 OK0; OK\n";
        print "Content-type: text/uri-list0; text/uri-list\n\n\n";
        print "#$urn0; "#$urn\n";
        return;
    }
    if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
      print "Status: 200 OK0; OK\n";
      print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ns</title></head>0; I2Ns</title></head>\n";
      print "<BODY>0; "<BODY>\n";
      print "<h1>URN $urn resolves to the following URNs:</h1>0; URNs:</h1>\n";
      print "<hr><ul>0; "<hr><ul>\n";
      print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
      return;
    }
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
    if ($accept =~ /text/uri-list/) /text\/uri-list/) {
        print "Status: 200 OK0; OK\n";
        print "Content-type: text/uri-list0; text/uri-list\n\n\n";
        print "#$urn0; "#$urn\n";
        return;
    }
    if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
        print "Status: 200 OK0; OK\n";
        print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
        print "<head><title>URN Resolution: I2Ns</title></head>0; I2Ns</title></head>\n";
        print "<BODY>0; "<BODY>\n";
        print "<h1>URN $urn resolves to the following URNs:</h1>0; URNs:</h1>\n";
        print "<hr><ul>0; "<hr><ul>\n";
        print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
        return;
    }
  }
  &urn_error("404 Not Found0); Found\n");
}

sub end {
  my($inarg)=@_;
  return $inarg . "st" if ($inarg =~ /1$/);
  return $inarg . "nd" if ($inarg =~ /2$/);
  return $inarg . "rd" if ($inarg =~ /3$/);
  return $inarg . "th";
}

sub resolve1 {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme, $value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  if (!defined $cite{$scheme}) {
    &urn_error("404 Not Found0); Found\n");
  }

  $flag = 0;
  open(INPUT, "$cite{$scheme}");
  while (<INPUT>) {
    $flag = 1 if (/^0*$value /);
    if ($flag == 1) {
      last if (/^$/);
      chop;
      push @bib,$_;
    }
  }

  $k=join " ",@bib;
  while ($k =~ /(fyi|std|rfc|bcp)([0-9]+)(.*)/i) /(\S*)\s*(fyi|std|rfc|bcp)\s*([0-9]+)(.*)/i) {
    $k=$4;
    $a=$2; $b=$3;
    if (($a ne $scheme || $b ne $value) && ($1 !~ /obso/i)){
      $a =~ tr/A-Z/a-z/;
      $b =~ s/^0*//;
      push @ref,"urn:ietf:$a:$b";
    }
  }

MIME_SWITCH: {
    if ($accept =~ /text/uri-list/) /text\/uri-list/) {
        print "Status: 200 OK0; OK\n";
        print "Content-type: text/uri-list0; text/uri-list\n\n\n";
        print "#$urn0; "#$urn\n";
        foreach $i (@ref) {
            print "$i0; "$i\n";
        }
        last MIME_SWITCH;
    }
  if ($accept =~ /text/html/) /\*\/\*|text\/html/) {
    print "Status: 200 OK0; OK\n";
    print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
    print "<head><title>URN Resolution: I2Ns</title></head>0; I2Ns</title></head>\n";
    print "<BODY>0; "<BODY>\n";
    print "<h1>URN $urn resolves to the following URNs:</h1>0; URNs:</h1>\n";
    print "<hr><ul>0; "<hr><ul>\n";
        foreach $i (@ref) {
            print "<li>$i: Click to resolve using0; using\n";
            print "<a href=
href=\"http://$host:$port/uri-res/I2C?$i\">I2C</a>,\n";
            print "<a href=
href=\"http://$host:$port/uri-res/I2L?$i\">I2L</a>,\n";
            print "<a href=
href=\"http://$host:$port/uri-res/I2Ls?$i\">I2Ls</a>,\n";
            print "<a href=
href=\"http://$host:$port/uri-res/I2R?$i\">I2R</a>,\n";
            print "<a href=
href=\"http://$host:$port/uri-res/I2Rs?$i\">I2Rs</a>\n";
        }
    print "</UL>0/body>0/HTML>0; "</UL>\n</body>\n</HTML>\n";
  }
}
}

sub make_link {
  my($sc);
  my($inarg)=@_;
  ($sc=$1) if ($inarg =~ /([a-z]*)/);
  return "/$sc/$inarg.ps" if (-e "/ftp/$sc/$inarg.ps");
  return "/$sc/$inarg.html" if (-e "/ftp/$sc/$inarg.html");
  return "/$sc/$inarg.txt";
}

sub urn_error {
  my($code) = @_; #store failure code here...

  print "Status: $code";
  print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2Ns $code</title></head>0; $code</title></head>\n";
  print "<BODY>0; "<BODY>\n";
  print "<h1>URN to URN resolution failed for the URN:</h1>0; URN:</h1>\n";
  print "<hr><h3>$urn</h3>0; "<hr><h3>$urn</h3>\n";
  print "</body>0; "</body>\n";
  print "</html>0; "</html>\n";
  exit;
};

A.5 I2R

#!/usr/local/bin/perl

use strict;

#
# this is a URN 2 resource resolver for the ietf namespace
#

my(%pathbase) = (
  rfc => "rfc/rfc",
  fyi => "fyi/fyi",
  std => "std/std",
  bcp => "bcp/bcp",
  id => "internet-drafts/draft-"
);

my(%number2date) = (
  44 => "99mar",
  43 => "98dec", 42 => "98aug", 41 => "98apr",
  40 => "97dec", 39 => "97aug", 38 => "97apr",
  37 => "96dec", 36 => "96jun", 35 => "96mar",
  34 => "95dec", 33 => "95jul", 32 => "95apr",
  31 => "94dec", 30 => "94jul", 29 => "94mar",
  28 => "93nov", 27 => "93jul", 26 => "93mar",
  25 => "92nov", 24 => "92jul", 23 => "92mar",
  22 => "91nov", 21 => "91jul", 20 => "91mar",
  19 => "90dec" );

my($wgpath) = "/ftp/ietf";
my($urn) = $ENV{'QUERY_STRING'};
my($host) = $ENV{'SERVER_NAME'}; #get my host name for ftp: URLs
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

print "$urn0; "$urn\n";
(&resolveid($1), exit) if ($urn =~ /urn:ietf:id:(i); /urn:ietf:id:(\S+)/i);

(&resolve1($1, $2), exit) if ($urn =~ /urn:ietf:(72)/i); /urn:ietf:(\w*):(\d*)/i);
(&resolve2($1, $2), exit) if ($urn =~ /urn:ietf:mtg-(9*)-(
120&urn_error("400 /urn:ietf:mtg-(\d*)-(\w*)/i);
&urn_error("400 Bad Request0); Request\n");

sub resolve2 {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found0) Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
      print "Status:  200 OK0; OK\n";
      print "Content-type: text/plain0; text/plain\n\n";
      open(FILE, "$link");
      while (<FILE>) {
          print $_;
      }
      close FILE;
    return;
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
      print "Status:  200 OK0; OK\n";
      print "Content-type: text/plain0; text/plain\n\n";
      open(FILE, "$link");
      while (<FILE>) {
          print $_;
      }
      close FILE;
    return;
  }
  &urn_error("404 Not Found0); Found\n");
}

sub end {
  my($inarg)=@_;
  return $inarg . "st" if ($inarg =~ /1$/);
  return $inarg . "nd" if ($inarg =~ /2$/);
  return $inarg . "rd" if ($inarg =~ /3$/);
  return $inarg . "th";
}

sub resolve1 {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme, $value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($txttry)="/ftp/$pathbase{$scheme}$value.txt";
  my($pstry)="/ftp/$pathbase{$scheme}$value.ps";
  my($htmltry)="/ftp/$pathbase{$scheme}$value.html";
MIME_SWITCH: {
    if ($accept =~ /application/postscript/ /application\/postscript/ && -f $pstry) {
      print "Status:  200 OK0; OK\n";
      print "Content-type: application/postscript0; application/postscript\n\n";
      open(FILE, "$pstry");
      while (<FILE>) {
          print $_;
      }
      close FILE;
      last MIME_SWITCH;
    }
    if ($accept =~ /text/html/ /text\/html/ && -f $htmltry) {
        print "Status:  200 OK0; OK\n";
        print "Content-type: text/html0; text/html\n\n";
        open(FILE, "$htmltry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    if ($accept =~ /text/plain/ /\*\/\*|text\/plain/ && -f $txttry) {
        print "Status:  200 OK0; OK\n";
        print "Content-type: text/plain0; text/plain\n\n";
        open(FILE, "$txttry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    &urn_error("404 Not Found0); Found\n");
  }
}

sub resolveid {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link);
  my($scheme) = "id";
  my($value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($txttry)="/ftp/$pathbase{$scheme}$value.txt";
  my($pstry)="/ftp/$pathbase{$scheme}$value.ps";
  my($htmltry)="/ftp/$pathbase{$scheme}$value.html";
MIME_SWITCH: {
    if ($accept =~ /application/postscript/ /application\/postscript/ && -f $pstry) {
      print "Status:  200 OK0; OK\n";
      print "Content-type: application/postscript0; application/postscript\n\n";
      open(FILE, "$pstry");
      while (<FILE>) {
          print $_;
      }
      close FILE;
      last MIME_SWITCH;
    }
    if ($accept =~ /text/html/ /text\/html/ && -f $htmltry) {
        print "Status:  200 OK0; OK\n";
        print "Content-type: text/html0; text/html\n\n";
        open(FILE, "$htmltry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    if ($accept =~ /text/plain/ /\*\/\*|text\/plain/ && -f $txttry) {
        print "Status:  200 OK0; OK\n";
        print "Content-type: text/plain0; text/plain\n\n";
        open(FILE, "$txttry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    &urn_error("404 Not Found0); Found\n");
  }
}

sub urn_error {
  my($code) = @_; #store failure code here...

  print "Status:  $code";
  print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2R $code</title></head>0; $code</title></head>\n";
  print "<BODY>0; "<BODY>\n";
  print "<h1>URN to URL resolution failed for the URN:</h1>0; URN:</h1>\n";
  print "<hr><h3>$urn</h3>0; "<hr><h3>$urn</h3>\n";
  print "</body>0; "</body>\n";
  print "</html>0; "</html>\n";
  exit;
}

A.6 I2Rs

#!/usr/local/bin/perl

use strict;

#
# this is a URN 2 resources resolver for the ietf namespace
#

my(@urls);

my(%pathbase) = (
  rfc => "rfc/rfc",
  fyi => "fyi/fyi",
  std => "std/std",
  bcp => "bcp/bcp",
  id => "internet-drafts/draft-"
);

my(%number2date) = (
  44 => "99mar",
  43 => "98dec", 42 => "98aug", 41 => "98apr",
  40 => "97dec", 39 => "97aug", 38 => "97apr",
  37 => "96dec", 36 => "96jun", 35 => "96mar",
  34 => "95dec", 33 => "95jul", 32 => "95apr",
  31 => "94dec", 30 => "94jul", 29 => "94mar",
  28 => "93nov", 27 => "93jul", 26 => "93mar",
  25 => "92nov", 24 => "92jul", 23 => "92mar",
  22 => "91nov", 21 => "91jul", 20 => "91mar",
  19 => "90dec" );

my($wgpath) = "/ftp/ietf";
my($urn) = $ENV{'QUERY_STRING'};
my($host) = $ENV{'SERVER_NAME'}; #get my host name for ftp: URLs
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

(&resolveid($1), exit) if ($urn =~ /urn:ietf:id:()/i); /urn:ietf:id:(\s*)/i);
(&resolve1($1, $2), exit) if ($urn =~ /urn:ietf:(72)/i); /urn:ietf:(\w*):(\d*)/i);
(&resolve2($1, $2), exit) if ($urn =~ /urn:ietf:mtg-(9*)-(
120&urn_error("400 /urn:ietf:mtg-(\d*)-(\w*)/i);
&urn_error("400 Bad Request0); Request\n");

sub resolve2 {
  my($ietfnum, $sesnam) = @_;
  my(@vers,$i);
  &urn_error("404 Not Found0) Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
      push(@vers,$link);
  }
  $link="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
      push(@vers,$link);
  }
  &urn_error("404 Not Found0) Found\n") if ($#vers==-1);

  print "Status: 200 OK0; OK\n";
  print "Content-type: multipart/alternative; boundary=endpart0; boundary=endpart\n\n";
  foreach $i (@vers) {
      print "--endpart0; "--endpart\n";
      if ($i =~ /html$/) {
          print "Content-Type: text/html0; text/html\n\n";
      }
      if ($i =~ /txt$/) {
          print "Content-Type: text/plain0; text/plain\n\n";
      }
      if ($i =~ /ps$/) {
          print "Content-Type: application/postscript0; application/postscript\n\n";
      }
      open(FILE, "$i");
      while (<FILE>) {
          print "$_";
      }
      close FILE;
  }
  print "--endpart0; "--endpart\n";
}

sub resolve1 {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link,@vers);
  my($scheme, $value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($try)="/ftp/$pathbase{$scheme}$value.txt";
  if (-f $try) {
      push(@vers, $try);
  }
  $try="/ftp/$pathbase{$scheme}$value.ps";
  if (-f $try) {
      push(@vers, $try);
  }
  $try="/ftp/$pathbase{$scheme}$value.html";
  if (-f $try) {
      push(@vers, $try);
  }
  print "Status: 200 OK0; OK\n";
  print "Content-type: multipart/alternative; boundary=endpart0; boundary=endpart\n\n";
  foreach $i (@vers) {
      print "--endpart0; "--endpart\n";
      if ($i =~ /html$/) {
          print "Content-Type: text/html0; text/html\n\n";
      }
      if ($i =~ /txt$/) {
          print "Content-Type: text/plain0; text/plain\n\n";
      }
      if ($i =~ /ps$/) {
          print "Content-Type: application/postscript0; application/postscript\n\n";
      }
      open(FILE, "$i");
      while (<FILE>) {
          print "$_";
      }
      close FILE;
  }
  print "--endpart0; "--endpart\n";
}

sub resolveid {
  my($flag,@bib,$i,$k,$j,$done,@ref);
  my($l,$link,@vers);
  my($scheme) = "id";
  my($value) = @_;
  $scheme =~ tr/A-Z/a-z/;
  &urn_error("404 Not Found0)if Found\n")if (!defined $pathbase{$scheme});
  my($try)="/ftp/$pathbase{$scheme}$value.txt";
  if (-f $try) {
      push(@vers, $try);
  }
  $try="/ftp/$pathbase{$scheme}$value.ps";
  if (-f $try) {
      push(@vers, $try);
  }
  $try="/ftp/$pathbase{$scheme}$value.html";
  if (-f $try) {
      push(@vers, $try);
  }
  print "Status: 200 OK0; OK\n";
  print "Content-type: multipart/alternative; boundary=endpart0; boundary=endpart\n\n";
  foreach $i (@vers) {
      print "--endpart0; "--endpart\n";
      if ($i =~ /html$/) {
          print "Content-Type: text/html0; text/html\n\n";
      }
      if ($i =~ /txt$/) {
          print "Content-Type: text/plain0; text/plain\n\n";
      }
      if ($i =~ /ps$/) {
          print "Content-Type: application/postscript0; application/postscript\n\n";
      }
      open(FILE, "$i");
      while (<FILE>) {
          print "$_";
      }
      close FILE;
  }
  print "--endpart0; "--endpart\n";
}
sub urn_error {
  my($code) = @_; #store failure code here...

  print "Status: $code";
  print "Content-type: text/html0HTML>0; text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2Rs $code</title></head>0; $code</title></head>\n";
  print "<BODY>0; "<BODY>\n";
  print "<h1>URN to URL resolution failed for the URN:</h1>0; URN:</h1>\n";
  print "<hr><h3>$urn</h3>0; "<hr><h3>$urn</h3>\n";
  print "</body>0; "</body>\n";
  print "</html>0; "</html>\n";
  exit;
}