INTERNET-DRAFT Donald E. Eastlake 3rd Motorola Expires May 2002 November 2001 Mapping Between MIME Types, Content-Types, and URIs ------- ------- ---- ------ -------------- --- ---- Donald E. Eastlake 3rd Status of This Document Distribution of this document is unlimited. Comments should be sent to the author. This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. 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. Abstract Multipurpose Internet Mail Extension (MIME) Content-Type headers, the MIME types used therein, and Uniform Resource Identifiers (URIs) are being used, in different contexts, to label entities. A mapping is specified such that the union of their meaning can be expressed in either URI or Content-Type syntax. D. Eastlake 3rd [Page 1] INTERNET-DRAFT Mapping Between Content-Types & URIs Table of Contents Status of This Document....................................1 Abstract...................................................1 Table of Contents..........................................2 1. Introduction............................................3 1.1 Introduction to URIs and MIME Type/Content-Type........3 1.2 Definitions and Conventions............................4 1.3 Additional Features....................................5 1.4 Overview of Remaining Sections.........................5 2. Mapping of Content-Type to URI..........................5 2.1 Simple Mapping of MIME Type to URI.....................6 2.2 Mapping of Full Content-Type to URI....................7 2.3 Content-Type Mapping Special Case for Closure..........7 2.4 Controlled Mapping of a Content-Type to a URI..........8 3. Mapping of URI to Content-Type..........................9 3.1 Simple Mapping of URI to Content-Type..................9 3.2 URI Mapping Special Case for Basic Closure............10 3.3 Controlled Mapping of a URI to a Content-Type.........10 4. Troublesome Characters.................................11 5. IANA Considerations and Potential Conflicts............11 6. Security Considerations................................12 Appendix..................................................13 References................................................17 Author's Address..........................................19 Expiration and File Name..................................19 D. Eastlake 3rd [Page 2] INTERNET-DRAFT Mapping Between Content-Types & URIs 1. Introduction Both MIME types and URIs have come to be used for type labeling and similar information. Both new MIME types and XML applications using new URIs for type labeling are continuing to be created and there does not appear to be any prospect that either syntax will become so dominant that the other will wither. In most protocols where there are provisions for a general "type label", the label is restricted to the syntax of a URI or the syntax of a Content-Type. In some cases, it will be useful to be able to express labels which already exist in the "other" syntax. That is, it may be useful in a URI syntax slot to also be able to express a MIME type or Content-Type and, conversely, it may be useful in a Content- Type syntax slot to also be able to express a URI. Ability to express Content-Types as URIs makes is easy to talk about them in [RDF] or other languages which refer to things with URIs. If one is sending, via SMTP, HTTP, or any other protocol using Content- Types, keying material or other things typed by the URI format type labels specified in [RFC 3075] or [XMLENC] it is convenient to be able to express such URI type labels as a Content-Type header. In the SMIL 2.0 case of the systemComponent attribute, there is a specific URI format attribute intended to contain Content-Type information [SMIL]. These are just a few specific examples that need a way to convert between URI and Content-Type syntax. This document specifies how to map any Content-Type into a URI and vice versa. 1.1 Introduction to URIs and MIME Type/Content-Type The IETF Multipurpose Internet Mail Extensions (MIME) message body standards have developed into a general tagging and bagging mechanism. This mechanism has spread from SMTP mail to USENET, HTTP, and other protocols. In MIME, the type of an object is given in a "Content-Type" header line. [RFC 2045, 2046, 2048] Such a line consists of a MIME type and, optionally, additional parameters. A MIME type consists of a MIME top level type, a slash, and a MIME subtype. The original Uniform Resource Locator (URL [RFC 1738]), used to point to World Wide Web (WWW) resources, has grown into the more general Uniform Resource Identifier (URI [RFC 2396]). Increasingly URIs are used as general labels for algorithms [RFC 3075], XML namespaces [XML NAME], web based protocol data types, etc. (In some of these label uses, URIs are considered opaque while in other cases they are assumed to be de-referencable into something which explicates their D. Eastlake 3rd [Page 3] INTERNET-DRAFT Mapping Between Content-Types & URIs meaning.) 1.2 Definitions and Conventions Concerning URIs, please note the following: (1) In this document, the term URI is used to include URI Reference. That is, it includes the case where an octothorpe ("#") followed by a fragment identifier is suffixed to a pure URI. (2) Only absolute URIs are mappable. Relative URIs, with just a hierarchical part, are not included in URI as used in this document. They must first be converted to absolute URIs as described in [RFC 2396]. (3) For presentation purposes, URIs are shown inside angle brackets ("<...>") but these angle brackets are not actually a part of the URI. Concerning Content-Types, please note the following: Content-Type values are shown preceded by "Content-Type: " and, when long, they are line folded as per [RFC 2822]. This prefix and line folding are for presentation purposes and are not actually a part of the Content-Type. Concerning "URL" encoding/decoding, please note the following: These are operations on character strings represented by octet sequences. URL encoding is the process of replacing certain one octet characters with the three octets for the character percent sign ("%") followed by two hex digits for the value of the octet replaced. URL decoding is the inverse process. I.E., replacing all three octet sequences which start with the octet for percent sign and the remainder of which consists of two hex digits (0-9, A-F, and a-f) with a single octet whose value was represented by the two hex digit sequence. The characters that are replaced by URL encoded for the purposes of this draft are listed in Section 4. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119]. D. Eastlake 3rd [Page 4] INTERNET-DRAFT Mapping Between Content-Types & URIs 1.3 Additional Features Note that a URI or Content-Type could get converted back and forth multiple times between these two syntaxes. To stop such multiple conversions from resulting in ever longer and more complex tags, a check is mandated so that if a conversion is of a previously converted syntax, the previous conversion is reversed, in so far as practical. To improve the repeatability of the results from single or multiple steps of syntax conversion, capitalization and punctuation recommendations are made where tokens are case insensitive or variable punctuation is allowed. Finally, in cases where the default conversion does not provide for sufficient control, optional elements are defined for inclusion in URIs and Content-Types that provide substantial control over the mapping output. 1.4 Overview of Remaining Sections Sections 2 and 3 below give an explanation of the mapping specified, more or less in English. The material is organized to start with the simplest and most common rules and then add exceptions for special cases and additional user control. Section 4 lists characters that must be "URL" ("%") encoded when mapping between URI and Content-Type. Section 5 covers IANA Considerations and potential conflicts. Section 6 give Security Considerations. The Appendix presents some sample code in Perl. 2. Mapping of Content-Type to URI This section starts with how to map a simiple MIME type to a URI, in Section 2.1. In 2.2, this is expanded to mapping a full Content-Type with parameters. Section 2.3 adds the special check for the mapping of a Content-Type which appears to have originally come from a URI. And Section 2.4 describes how to control the mapping through a special Content-Type parameter. D. Eastlake 3rd [Page 5] INTERNET-DRAFT Mapping Between Content-Types & URIs 2.1 Simple Mapping of MIME Type to URI For the simplest case of a Content-Type consisting of just a MIME type, create a URI with scheme "ContentType" and a scheme dependent part consisting of the MIME type. For example Content-Type: image/JPEG simply converts to Because they can, in principle, contain many special characters, the top level MIME type and the MIME subtype are URL encoded. White space must be removed. Scheme names (the part before the first ":" in a URI) are case insensitive but for readability and repeatability, the capitalization "ContentType" SHOULD be used. Similarly, MIME top level types and subtypes (the fields before and after the "/" in a MIME type field, respectively) are case insensitive but SHOULD be all lower cased when mapped to the URI form. For example Content-type: x-FOO?bar/biZZare#sUb#tYpe converts to ContentType:x-foo%3Fbar/bizzare%23sub%23type Scheme names (the part before the first ":" in a URI) are case insensitive but for readability and repeatability, the capitalization "ContentType" SHOULD be used. Similarly, MIME top level types and subtypes (the fields before and after the "/" in a MIME type field, respectively) are case insensitive but SHOULD be all lower cased when mapped to the URI form. Note: There is no "//" after the "ContentType:" scheme as used herein. Such a "//" would imply a specific structuring of the scheme dependent part appearing in the URI after the "ContentType:" as defined in [RFC 2396]. Since that full structuring is not used, "//" is not used. The meaning of URIs starting with "ContentType://" is reserved for future definition. Note: "Content-Type", with hyphen, is syntactically allowed as a scheme name. However, [RFC 2717] reserves embedded hyphens in scheme names to indicate the prefix of an alternate tree of scheme names. Therefore, the un-hyphenated ContentType is used. D. Eastlake 3rd [Page 6] INTERNET-DRAFT Mapping Between Content-Types & URIs 2.2 Mapping of Full Content-Type to URI A Content-Type header frequently includes more than just the mandatory MIME type. It can also have type dependent parameters, including private parameters, such as Content-Type: text/plain; charset="us-ascii"; x-mac-type="54455854"; x-mac-creator="4D4F5353" Content-Type: image/tiff; application=faxbw Content-Type parameters are mapped into a "query portion" suffix of the URI in much the same way that HTML form fields [HTML] are. That is, they are concatenated to the MIME type after a "?" and, if there is more than one parameter, separated by "&". White space is not allowed in URIs so it must be removed. Thus the above Content-Types would be mapped into the following URIs: Parameter values in the mapped URI MUST always be enclosed in double quotes ('"'). If the Content-Type has a trailing ";" but no parameters, then "?" SHOULD NOT be added to the URI. Note: Any occurrences of the "&" separator will have to be encoded as "&" or other appropriate character reference if the URI is used in XML outside a CDATA construct, or most other SGML derived languages. However, "&" is the standard separator used in CGI (Common Gateway Interface) parsing of query section parameters for "mailto:" [RFC 2368], "http:", etc., schemes. On balance, the continued use of "&" has been chosen. 2.3 Content-Type Mapping Special Case for Closure A URI may have been converted to a Content-Type and get converted back. To stop this from resulting in an ever more complex syntax, a check MUST be made to see if the MIME subtype of a Content-Type being converted is in the "uri." subtype tree (see section 2.2 above). If so, the URI is computed from the subtype by stripping the "uri." prefix and doing one level of URL decoding. The top level MIME type is ignored in this case. In addition, Content-Type parameters, if any, are added as a "query portion" and a "URI-fragment" parameter is added as a fragment after URL decoding. D. Eastlake 3rd [Page 7] INTERNET-DRAFT Mapping Between Content-Types & URIs For example: Content-Type: application/uRI.mailto%3Auser%40host.example Content-Type: application/uri.http%3A%2F%2Fx.test; foo="123"; bar="abcd" Content-Type: application/uri.http%3A%2F%2Fa%3Ab%40c.text%2Fx%2Fy; URI-fragment="z%25z" are mapped to Note: If a Content-Type or MIME Type is being written by a user and they know that there is a URI which is a more natural expression of the labeling desired, they can simply use an ".../uri." MIME Type to start with. 2.4 Controlled Mapping of a Content-Type to a URI There will be cases where greater control over the mapping is desired. These are cases where a more natural URI exists rather than the automatic "ContentType" URI scheme. To accomplish this controlled mapping starting with a Content-Type, a special Content-Type parameter "URI-body" is defined. If a Content- Type does not have a MIME subtype in the "uri." tree and this parameter is present, it is URL decoded for the non-query portion of the URI mapped to and the original MIME top level and sub types are URL encoded and preserved in a URI query parameter called "MIME- type". For example Content-Type: application/xml; URI-body="http://xml.example/foo" would map to D. Eastlake 3rd [Page 8] INTERNET-DRAFT Mapping Between Content-Types & URIs 3. Mapping of URI to Content-Type Section 3.1 below describes the basic mapping of a URI into a Content-Type. Section 3.2 specifies the exceptional processing when a URI being converted to a Content-Type appears to have previously been converted from a Content-Type. And Seciton 3.3 provides for greater control over the mapping when needed. 3.1 Simple Mapping of URI to Content-Type In the basic case, a URI maps to a Content-Type with a top level MIME type of "application" and a MIME sub-type in the "uri." tree. The "uri." is followed by the URL encoding of the URI exluding the query and fragment parts. Any "query" parameters in the URI are mapped to Content-Type parameters and, if the URI ends with a fragment identifier, it is URL encoded and mapped to the special Content-Type parameter "URI-fragment". Note: Current URI syntax permits scheme dependent parts in which "?" does not indicate a query section; however, no such syntaxes have been publicly defined. Some examples of the basic case follow: convert to Content-Type: application/uri.http%3A%2F%2Fexample.com%2Ftag42 Content-Type: application/uri.mailto%3AU%40example.net; subject="misc"; body="line1%250D%250Aline2" Content-Type: application/uri.xyz%3A%2F%2Fabc.test%2Fdef; h="ijk"; URI-fragment="lmn" Content-Type parameters values extracted from the query portion of a URI MUST be surrounded with double quotes ('"'). When URI encoding, if the hex value has any letters (a-f) in it, they SHOULD be upper cased. D. Eastlake 3rd [Page 9] INTERNET-DRAFT Mapping Between Content-Types & URIs 3.2 URI Mapping Special Case for Basic Closure It is desirable that an arbitrary Content-Type be recovered semantically intact when mapped to a URI and then that URI is mapped back to a Content-Type. To approximate this, the following special case is added to the simple case described in section 3.1 above. If the URI scheme is "ContentType:", then the Content-Type is computed from the remaining part of the URI (the scheme specific part), by replacing the first question mark ("?") and all subsequent ampersands ("&") with semi-colon space ("; "), and then undoing one level of URI encoding, i.e., replacing percent sign ("%") followed by two hex digits with the character having that hex value. For example are mapped to Content-Type: model/vnd.example.longish.sub#type.name Content-Type: text/plain; charset="US-ASCII"; x-obscure="value" Note: A URI produced by simple mapping from a normal Content-Type will never have a fragment suffix. If one appears, it should be mapped into a URI-fragment parameter, as specified in Section 3.1. Note: If a type label URI is being written by a user and they know that there is a Content-Type which is a more natural expression of the labeling desired, they can simply use a "ContentType:" scheme to start with. 3.3 Controlled Mapping of a URI to a Content-Type There will be cases where greater control over the mapping is desired. These are cases where a more natural Content-Type exists than the "uri." MIME subtype under the "application" type. To accomplish this controlled mapping starting with a URI, a special query part parameter "MIME-type" is defined. If a URI is not of scheme ContentType and this special parameter is found, then the MIME type is set to the parameter value URL decoded and the URI body (all of the URI except "query" parameters and any fragment identifier) is preserved in a URL encoded "URI-body" Content-Type parameter. D. Eastlake 3rd [Page 10] INTERNET-DRAFT Mapping Between Content-Types & URIs For example would map to Content-Type: message/rfc822; URI-body="mailto%3Ajoe%40blow.text"; URI-fragment="123" 4. Troublesome Characters Troublesome characters are defined as those not permitted in a token in [RFC 2045] with the addition of percent sign and octothorpe. That is, any character code from 0 through 32 inclusive and character code 127 and any of "(", ")", "<", ">", "@", ",", ";", ":", "\", "/", "[", "]", "?", "%", "#", '"', and "=" are troublesome characters. 5. IANA Considerations and Potential Conflicts This document allocates and specifies the following: (1) The "ContentType" URI scheme. (2) The "uri." MIME subtype tree. Since this subtree is totally delegated to the URI specification, there are no independent publication or review requirements for it. Any valid URI can be used after the "uri." in any MIME top level type, after troublesome characters (see section 4) in the URI are URL encoded. (3) In the context of URI to Content-Type mapping, a meaning is specified for the "MIME-type" URI query section parameter. (4) In the context of automatic Content-Type to URI mapping, a meaning is specified for the "URI-body" and "URI-fragment" Content-Type parameters. Because this document specifies the "ContentType" URI scheme and the "uri." MIME subtype tree, no conflict can arise due to other uses of them. However, there has been no precedent for the specification of Content-Type parameters valid across all MIME types, such as URI-body and URI-fragment, and in fact [RFC 2046] denies their possibility. Nor has there been any precedent for the specification of a universal D. Eastlake 3rd [Page 11] INTERNET-DRAFT Mapping Between Content-Types & URIs URI query parameter such as MIME-type. The probability that any different use is currently being made or will in the foreseeable future have to be made of these names is low enough that it can be ignored. It is possible that some processing systems are sensitive to the presence of parameters they do not understand and will indicate errors when presented with controlled mapping URIs or Content-Types. However, Content-Type parameters and URI query parameters are usually handled on receipt by such mechanisms as storing the name-value pair in an associative array or as "environment variables" and ignoring extra parameters. In fact, Content-Type processors are required by [RFC 2046] to ignore any parameters they do not understand and to ignore parameter order. 6. Security Considerations In some sense, the security considerations for MIME and content types [RFC 2046], URIs [RFC 2396], and for every individual MIME type and URI scheme can apply. In addition, the deployment of mapping aware software may enable the introduction into or transmission through MIME or Content-Type contexts of URI semantics, including possibly dangerous action schemes such as "mailto", and the introduction into or transmission through URI contexts of MIME and content type semantics, including possibly dangerous executable data types or the like. Finally, implementation of controlled mapping may enable a malicious user, by adding one of the special parameters specified herein, to cause a surprising change in the semantics of a URI or Content-Type produced by the mapping from an apparently innocuous Content-Type or URI. Particular case should be given to screen the characters resulting from URL decoding into sensitive fields. D. Eastlake 3rd [Page 12] INTERNET-DRAFT Mapping Between Content-Types & URIs Appendix The following Perl code implements much of the mapping given in Sections 2 and 3 above: # Content-Type and URI intermapping exampel code # Donald E. Eastlake 3rd, November 2001 # ----------- # test driver # ----------- use strict; print "Type a Content-Type, a URI, or 'Quit'. Do NOT include\n"; print "angle brackets around the URI or a 'Content-Type:' prefix.\n\n"; while ( ) # get test input { my $test; chomp ( $_ ); if ( /^\s*([-\w\.+]+:[^\s]*)/ ) #test for URI { print "<$1>\n"; # echo $test = uri2ct ( $1 ); print " Content-Type: ", $test, "\n"; $test = ct2uri ( $test ); print "<$test>\n"; # converted back } elsif #test for Content-Type ( m=^\s*([-_\w\.+#\$%!\?]+/[-_\w\.+#\$%!\?]+.*)= ) # (note: RFC 2405 allows other characters in type and subtype) { print "Content-Type: $1\n"; # echo $test = ct2uri ( $1 ); print " <", $test, ">\n"; $test = uri2ct ( $test ); print "Content-Type: $test\n"; # converted back } elsif ( /^\s*$/ ) elsif ( /exit|quit|halt|stop|end/i ) { last; } else { print "BAD INPUT: $_\n"; } print "\n"; } print "EXIT\n"; sleep 1; exit; # --------------------------- # convert URI to Content-Type # --------------------------- D. Eastlake 3rd [Page 13] INTERNET-DRAFT Mapping Between Content-Types & URIs sub uri2ct ($) { my $result; my $item; my %paramh; my @paraml; @_[0] =~ m=\s*([^:/?#]+)?:([^?#]*)(\?([^#]*))?(#([^\s]*))?=; # 1 2 3 4 5 6 my $scheme = lc ( $1 ); my $main = $2; @paraml = split ( /&/, $4 ); foreach $item (@paraml) { $item =~ /([^=]+)=(.*)/; $paramh{ lc ( $1 ) } = $2; } if ( $scheme eq "contenttype" ) { $result = yestrouble ( $main ); } elsif ( $result = $paramh{"mime-type"} ) { delete ( $paramh{"mime-type"} ); $result =~ s/^"(.*)"$/$1/; $result = yestrouble ( $result ) . '; URI-body="' . notrouble ( $scheme . ":" . $main ) . '"'; } else { $result = "application/uri." . notrouble ( $scheme . ":" . $main ); } if ( %paramh ) { my $key; my $value; while (( $key, $value ) = each ( %paramh )) { $result .= "; $key=" . dquote ( $value ); } } if ( $5 ) { $result .= '; URI-fragment="' . notrouble ( $6 ) . '"'; } return $result; } # end uri2ct # --------------------------- # convert Content-Type to URI # --------------------------- sub ct2uri ($) { my %paramh; my @paraml; my $result; my $item; my $fragment; @_[0] =~ m&^\s*([-_\w\.+#\$%!\?]+)/([-_\w\.+#\$%!\?]+)\s*(;\s*(.*))?&; # 1 2 3 4 my $type = lc ( notrouble ( $1 ) . "/" . notrouble ( $2 ) ); my $minor = lc ( $2 ); @paraml = split ( /\s*;\s*/, $4 ); D. Eastlake 3rd [Page 14] INTERNET-DRAFT Mapping Between Content-Types & URIs foreach $item ( @paraml ) { $item =~ /([^=\s]+)\s*=\s*(.*)/; $paramh{ lc ( $1 ) } = $2; } if ( $minor =~ /^uri\.(.*)/i ) { $result = yestrouble ( $1 ); } elsif ( $result = $paramh{"uri-body"} ) { delete ( $paramh{"uri-body"} ); $result = yestrouble ( $result ); $result =~ s/^"(.*)"$/$1/ ; $paramh{"MIME-type"} = $type; } else { $result = "ContentType:" . $type; } if ( $fragment = $paramh{"uri-fragment"} ) { delete ( $paramh{"uri-fragment"} ); $fragment =~ s/^"(.*)"$/$1/; } if ( %paramh ) { my $key; my $value; $result .= "?"; while (( $key, $value ) = each ( %paramh )) { $result .= $key . '=' . dquote ( $value ) . "&"; } chop ( $result ); # get rid of trailing & } if ( $fragment ) { $result .= '#' . yestrouble ( $fragment ) } return $result; } # end ct2uri # ------------------- # support subroutines # ------------------- # double quote string if not already double quoted # ------------------------------------------------ sub dquote ($) { my $string = @_[0]; if ( $string =~ /^".*"$/ ) { return $string; } return '"' . $string . '"'; } D. Eastlake 3rd [Page 15] INTERNET-DRAFT Mapping Between Content-Types & URIs # URL encode troublesome characters # --------------------------------- sub notrouble ($) { my $string = @_[0]; my $result; while ( $string =~ m{([^%\?\(\)<>@,;:\\/\[\]="#]*)([%\?\(\)<>@,;:\\/\[\]="#])(.*)} # 1 2 3 ) { $result .= "$1%" . sprintf ( "%02X", ord ( $2 ) ); $string = $3; } return $result . $string; } # end no trouble # decode URL encoded string # ------------------------- sub yestrouble ($) { my $string = @_[0]; my $result; while ( $string =~ /([^%]*)%([0-9a-fA-F]{2})(.*)/ ) { $result .= $1 . chr ( unhexify ( substr ( $2, 0, 1 ) ) * 16 + unhexify ( substr ( $2, 1, 1 ) ) ); $string = $3; } return $result . $string; } # end yestrouble # convert hex digit to corresponding integer # ------------------------------------------ sub unhexify ($) { my $num = ord (@_[0]); if ( $num >= ord ("0") && $num <= ord ("9") ) { return ( $num - ord ("0" ) ); } if ( $num >= ord ("A") && $num <= ord ("F") ) { return ( $num - ord ("A" ) + 10 ); } return ( $num - ord ("a" ) + 10 ); } D. Eastlake 3rd [Page 16] INTERNET-DRAFT Mapping Between Content-Types & URIs References [HTML] - Dave Raggett, Arnaud Le Hors, Ian Jacobs, "HTML 4.01 Specification", , December 1999. [RDF] - O. Lassila, R. Swick, "Resource Description Framework (RDF) Model and Syntax Specification", , 22 February 1999. [RFC 1738] - T. Berners-Lee, L. Masinter, M.McCahill, "Uniform Resource Locators (URL)", December 1994. [RFC 2045] - N. Freed & N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", November 1996. [RFC 2046] - N. Freed & N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", November 1996. [RFC 2048] - N. Freed, J. Klensin & J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", November 1996. [RFC 2119] - S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [RFC 2368] - P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL scheme", July 1998 [RFC 2396] - T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", August 1998. [RFC 2717] - R. Petke, I. King, "Registration Procedures for URL Scheme Names", November 1999. [RFC 2718] - L. Masinter, H. Alvestrand, D. Zigmond, R. Petke, "Guidelines for new URL Schemes", November 1999. [RFC 2822] - P. Resnick, Editor, "Internet Message Format", April 2001. [RFC 3075] - D. Eastlake, J. Reagle, D. Solo, "XML-Signature Syntax and Processing", March 2001. [SMIL] - "Synchronized Multimedia Integration Language (SMIL 2.0)", , 7 August 2001. [XML NAME] - Tim Bray, Dave Hollander, Andrew Layman, "Namespaces in XML", , 14 January 1999. D. Eastlake 3rd [Page 17] INTERNET-DRAFT Mapping Between Content-Types & URIs [XMLENC] - D. Eastlake, J. Reagle, "XML Encryption Syntax and Processing", , 18 October 2001. D. Eastlake 3rd [Page 18] INTERNET-DRAFT Mapping Between Content-Types & URIs Author's Address Donald E. Eastlake 3rd Motorola 155 Beaver Street Milford, MA 01757 USA Telephone: +1 508-261-5434 (w) +1 508-634-2066 (h) FAX: +1 508-261-4447 (w) EMail: Donald.Eastlake@motorola.com Expiration and File Name This draft expires May 2002. Its file name is draft-eastlake-cturi-03.txt. D. Eastlake 3rd [Page 19]