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Internet-Draft                                                Ryan Moats
draft-ietf-urn-ietf-05.txt                                          AT&T
Expires in six months                                           May 1998

                   A URN Namespace for IETF Documents
                  Filename: draft-ietf-urn-ietf-05.txt


Status of This Memo

      This document is an Internet-Draft.  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.''

      To view the entire list of current Internet-Drafts, please check
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      (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 and
   the minutes of working groups (WG) and birds of a feather (BOF)
   meetings that occur during IETF conferences.  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.







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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

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.

     Declared registrant of the namespace:

          Ryan Moats
          jayhawk@att.com

     Declaration of structure:

          The identifier has the following ABNF [2] specification:

          NSS = (family ":" number) / ("mtg-" number "-" wgbofname)
          family = "rfc" / "std" / "fyi" / "bcp"
          number = 1*DIGIT
          wgbofname = 1*LETDIGIT
          LETDIGIT = DIGIT / %x41-%x5a / %x61-%x7a
          DIGIT = %x30-%x39

          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.

     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" and
          "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.

     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 comprise 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 two
          ways.  The first is when a new RFC, FYI, STD or BCP is
          passed by the IESG and published 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.




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          The second way a URN is assigned is when a working
          group or birds of a feather files meeting minutes 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.

     Process of identifier resolution:

          A mirrored copy of the underlying documentation is
          required to resolve these URNs.  Resolution via
          HTTP is accomplished 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.

     Scope:

          Global.

3. 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.

4. 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.



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4. 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 Specifica-
            tions: ABNF," RFC 2234, November 1997.


5. 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) = (
       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) = (
       41 => "98apr",
       40 => "97dec", 39 => "97aug", 38 => "97apr",
       37 => "96dec", 36 => "96jun", 35 => "96mar",
       34 => "95dec", 33 => "95jul", 32 => "95apr",



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       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

     (&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\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$/);



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       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,$_;
         }
       }

       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";



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         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) {
             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]*)/);



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       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;
     };

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",
     );

     my(%number2date) = (
       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";



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     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

     (&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: 302 Moved temporarily\n";
         print "Location: $link\n";
         return;
       }
       my($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 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";
       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";



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           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");
       }
     }

     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;
     }

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"
     );



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     my(%number2date) = (
       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

     (&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";
         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";



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           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";
         }
         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");
       }



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       $try="/ftp/$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";
           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: I2Ls $code</title></head>\n";
       print "<BODY>\n";
       print "<h1>URN to URL resolution failed for the URN:</h1>\n";



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       print "<hr><h3>$urn</h3>\n";
       print "</body>\n";
       print "</html>\n";
       exit;
     }

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) = (
       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

     (&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";



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       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 "#$urn\n";
             return;
         }
         if ($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";
     }




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     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=$3;
         if (($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";



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             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...

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



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       fyi => "fyi/fyi",
       std => "std/std",
       bcp => "bcp/bcp"
     );

     my(%number2date) = (
       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

     (&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 $_;
           }



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           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";
       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");



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             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;
     }

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"
     );

     my(%number2date) = (
       41 => "98apr",
       40 => "97dec", 39 => "97aug", 38 => "97apr",
       37 => "96dec", 36 => "96jun", 35 => "96mar",
       34 => "95dec", 33 => "95jul", 32 => "95apr",



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       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

     (&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";
       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;



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

       print "Status: $code";



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       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;
     }










































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