Internet-Draft                                                Ryan Moats
draft-ietf-urn-ietf-09.txt                                          AT&T
Expires in six months                                           May 1999

                   A URN Namespace for IETF Documents
                  Filename: draft-ietf-urn-ietf-09.txt

Status of This Memo

      This document is an 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 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" 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.

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

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   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: 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 = rfc-nss / fyi-nss / std-nss / bcp-nss /
                      draft-nss / mtg-nss / other-nss

                rfc-nss = "rfc:" 1*DIGIT
                fyi-nss = "fyi:" 1*DIGIT
                std-nss = "std:" 1*DIGIT
                bcp-nss = "bcp:" 1*DIGIT
                draft-nss = "id:" string
                mtg-nss = "mtg:" string
                other-nss = string
                  ; beginning with a prefix other than one of those
                  ; above for future expansion

                string = 1*(DIGIT / ALPHA / "-")

                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

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                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:

                Relevant documentation is in draft-ietf-urn-ietf-09.

        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.  Immutability of RFCs, STDs,
                FYIs and BCPs is at the discretion of the RFC Editor.
                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

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                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 additional to resolution specified

        Scope:

                Global.

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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
           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 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

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

sub resolvemtg {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};

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

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

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      chop;
      push @bib,$_;
    }
  }

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

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        push @ref,"$1$2";
        $k=$3;
      }
      $done="";
      foreach $j (@ref) {
        next if ($done =~ $j);
        $done .= "$j ";
        $l = $j;
        $l =~ s/\s//g;
        $l =~ tr/A-Z/a-z/;
        $link=&make_link("$l");
        $bib[$i] =~ s/$j/<A HREF="$link">$j<\/A>/g;
      }
    }
    print "<HTML>\n<TITLE>Citation for $urn</TITLE>\n";
    print "<BODY>\n";
    $link=&make_link("$scheme$value");
    print "<H1><A HREF=\"$link\">$scheme$value</A>:</H1>\n";
    foreach $i (@bib) {
      print "$i\n";
    }
    print "</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/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2C $code</title></head>\n";
  print "<BODY>\n";
  print "<h1>URN to URC resolution failed for the URN:</h1>\n";
  print "<hr><h3>$urn</h3>\n";
  print "</body>\n";
  print "</html>\n";
  exit;
};

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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 OK\r\n";
                print "Content-type: text/html\r\n\r\n";
                print "<HTML>\n<TITLE>Citation for $urn</TITLE>\n";
                print "<BODY>\n";
                print "<a
href=\"http://blackhole.vip.att.net/internet-drafts/$l\">$l</a>:\n";
                print "<pre>\n";
                foreach $i (@bib) {
                  print "$i";
                }
                print "</pre>\n";
                print "</BODY>\n</HTML>\n";
                exit;
              }
            }
      }
      $flag = 0;
      @bib = ();
    }
  }
  &urn_error("404 Not Found\n");
}

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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-"
);

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

sub resolvemtg {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not 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 temporarily\n";
    print "Location: $link\n";

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    return;
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
    print "Status:  302 Moved temporarily\n";
    print "Location: $link\n";
    return;
  }
  &urn_error("404 Not 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 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/ && -f $pstry) {
      print "Status:  302 Moved temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.ps\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /text\/html/ && -f $htmltry) {
      print "Status:  302 Moved temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.html\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /\*\/\*|text\/plain/ && -f $txttry) {
      print "Status:  302 Moved temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.txt\n\n";
      last MIME_SWITCH;
    }
    &urn_error("404 Not Found\n");
  }
}

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

  print "Status:  $code";
  print "Content-type: text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2L $code</title></head>\n";
  print "<BODY>\n";
  print "<h1>URN to URL resolution failed for the URN:</h1>\n";
  print "<hr><h3>$urn</h3>\n";
  print "</body>\n";
  print "</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 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/ && -f $pstry) {
      print "Status:  302 Moved temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.ps\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /text\/html/ && -f $htmltry) {
      print "Status:  302 Moved temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.html\n\n";
      last MIME_SWITCH;
    }
    if ($accept =~ /\*\/\*|text\/plain/ && -f $txttry) {
      print "Status:  302 Moved temporarily\n";
      print "Location: http://$host/$pathbase{$scheme}$value.txt\n\n";
      last MIME_SWITCH;
    }
    &urn_error("404 Not Found\n");
  }
}

A.3 I2Ls

#!/usr/local/bin/perl

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

sub resolve2 {
  my($ietfnum, $sesnam) = @_;
  &urn_error("404 Not Found\n") if (!defined $number2date{$ietfnum});
  my($date)=$number2date{$ietfnum};
  my($link)="$wgpath/$sesnam/$sesnam-minutes-$date.txt";
  if (-f $link) {
    $link=~s/^\/ftp\///;
    my($ftplink)="ftp://$host/$link";
    my($httplink)="http://$host/$link";
    my($glink)="gopher://$host:70/0/$link";

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    if ($accept =~ /text\/uri-list/) { #look for text/uri-list, otherwise
text/html
      print "Status: 200 OK\n";
      print "Content-type: text/uri-list\n\n\n";
      print "#$urn\n";
      print "$ftplink\n";
      print "$httplink\n";
      print "$glink\n";
    }
    if ($accept =~ /\*\/\*|text\/html/) {
      print "Status: 200 OK\n";
      print "Content-type: text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ls</title></head>\n";
      print "<BODY>\n";
      print "<h1>URN $urn resolves to the following URLs:</h1>\n";
      print "<hr><ul>\n";
      print "<a href=\"$ftplink\">$ftplink</a>\n";
      print "<a href=\"$httplink\">$httplink</a>\n";
      print "<a href=\"$glink\">$glink</a>\n";
      print "</UL>\n</body>\n</HTML>\n";
    }
    return;
  }
  my($link)="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
    $link=~s/^\/ftp\///;
    my($ftplink)="ftp://$host/$link";
    my($httplink)="http://$host/$link";
    my($glink)="gopher://$host:70/0/$link";
    if ($accept =~ /text\/uri-list/) { #look for text/uri-list, otherwise
text/html
      print "Status: 200 OK\n";
      print "Content-type: text/uri-list\n\n\n";
      print "#$urn\n";
      print "$ftplink\n";
      print "$httplink\n";
      print "$glink\n";
    }
    if ($accept =~ /\*\/\*|text\/html/) {
      print "Status: 200 OK\n";
      print "Content-type: text/html\n\n<HTML>\n";
      print "<head><title>URN Resolution: I2Ls</title></head>\n";
      print "<BODY>\n";
      print "<h1>URN $urn resolves to the following URLs:</h1>\n";
      print "<hr><ul>\n";
      print "<a href=\"$ftplink\">$ftplink</a>\n";
      print "<a href=\"$httplink\">$httplink</a>\n";
      print "<a href=\"$glink\">$glink</a>\n";
      print "</UL>\n</body>\n</HTML>\n";
    }

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

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

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      foreach $i (@urls) {
        print "<LI><A HREF=\"$i\">$i</A>\n";
      }
      print "</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/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2L $code</title></head>\n";
  print "<BODY>\n";
  print "<h1>URN to URL resolution failed for the URN:</h1>\n";
  print "<hr><h3>$urn</h3>\n";
  print "</body>\n";
  print "</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 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");
  }

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

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

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  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) = $ENV={'SERVER_PORT'};
my($accept) = $ENV{'HTTP_ACCEPT'}; #this is the "Accept:" HTTP header

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

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

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        return;
    }
    if ($accept =~ /\*\/\*|text\/html/) {
        print "Status: 200 OK\n";
        print "Content-type: text/html\n\n<HTML>\n";
        print "<head><title>URN Resolution: I2Ns</title></head>\n";
        print "<BODY>\n";
        print "<h1>URN $urn resolves to the following URNs:</h1>\n";
        print "<hr><ul>\n";
        print "</UL>\n</body>\n</HTML>\n";
        return;
    }
  }
  &urn_error("404 Not 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 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 =~ /(\S*)\s*(fyi|std|rfc|bcp)\s*([0-9]+)(.*)/i) {
    $k=$4;
    $a=$2; $b=$3;

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

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  print "Status: $code";
  print "Content-type: text/html\n\n<HTML>\n";
  print "<head><title>URN Resolution: I2Ns $code</title></head>\n";
  print "<BODY>\n";
  print "<h1>URN to URN resolution failed for the URN:</h1>\n";
  print "<hr><h3>$urn</h3>\n";
  print "</body>\n";
  print "</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 "$urn\n";
(&resolveid($1), exit) if ($urn =~ /urn:ietf:id:(\S+)/i);

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

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

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  my($pstry)="/ftp/$pathbase{$scheme}$value.ps";
  my($htmltry)="/ftp/$pathbase{$scheme}$value.html";
MIME_SWITCH: {
    if ($accept =~ /application\/postscript/ && -f $pstry) {
      print "Status:  200 OK\n";
      print "Content-type: application/postscript\n\n";
      open(FILE, "$pstry");
      while (<FILE>) {
          print $_;
      }
      close FILE;
      last MIME_SWITCH;
    }
    if ($accept =~ /text\/html/ && -f $htmltry) {
        print "Status:  200 OK\n";
        print "Content-type: text/html\n\n";
        open(FILE, "$htmltry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    if ($accept =~ /\*\/\*|text\/plain/ && -f $txttry) {
        print "Status:  200 OK\n";
        print "Content-type: text/plain\n\n";
        open(FILE, "$txttry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    &urn_error("404 Not 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 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: {

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    if ($accept =~ /application\/postscript/ && -f $pstry) {
      print "Status:  200 OK\n";
      print "Content-type: application/postscript\n\n";
      open(FILE, "$pstry");
      while (<FILE>) {
          print $_;
      }
      close FILE;
      last MIME_SWITCH;
    }
    if ($accept =~ /text\/html/ && -f $htmltry) {
        print "Status:  200 OK\n";
        print "Content-type: text/html\n\n";
        open(FILE, "$htmltry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    if ($accept =~ /\*\/\*|text\/plain/ && -f $txttry) {
        print "Status:  200 OK\n";
        print "Content-type: text/plain\n\n";
        open(FILE, "$txttry");
        while (<FILE>) {
            print $_;
        }
        close FILE;
        last MIME_SWITCH;
    }
    &urn_error("404 Not Found\n");
  }
}

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

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

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

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

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  if (-f $link) {
      push(@vers,$link);
  }
  $link="$wgpath/$date/$sesnam-minutes-$date.txt";
  if (-f $link) {
      push(@vers,$link);
  }
  &urn_error("404 Not Found\n") if ($#vers==-1);

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

Expires 11/30/99                                               [Page 27]

INTERNET DRAFT     A URN Namespace for IETF Documents           May 1999

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

Expires 11/30/99                                               [Page 28]

INTERNET DRAFT     A URN Namespace for IETF Documents           May 1999

      }
      if ($i =~ /txt$/) {
          print "Content-Type: text/plain\n\n";
      }
      if ($i =~ /ps$/) {
          print "Content-Type: application/postscript\n\n";
      }
      open(FILE, "$i");
      while (<FILE>) {
          print "$_";
      }
      close FILE;
  }
  print "--endpart\n";
}
sub urn_error {
  my($code) = @_; #store failure code here...

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

Expires 11/30/99                                               [Page 29]