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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2234 (ref. 'ABNF') (Obsoleted by RFC 4234) Summary: 12 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Earhart 3 Internet Draft: ACAP-TYPE-EXT Carnegie Mellon 4 Document: draft-ietf-acap-type-ext-01.txt March 1998 5 Expires September 1998 7 ACAP TYPE Extension 9 Status of this Memo 11 This document is an Internet-Draft. Internet-Drafts are working 12 documents of the Internet Engineering Task Force (IETF), its areas, 13 and its working groups. Note that other groups may also distribute 14 working documents as Internet-Drafts. 16 Internet-Drafts are draft documents valid for a maximum of six 17 months. and may be updated, replaced, or obsoleted by other 18 documents at any time. It is not appropriate to use Internet-Drafts 19 as reference material or to cite them other than as "work in 20 progress". 22 To learn the current status of any Internet-Draft, please check the 23 1id-abstracts.txt listing contained in the Internet-Drafts Shadow 24 Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe), 25 munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or 26 ftp.isi.edu (US West Coast). 28 This document suggests a proposed protocol for the Internet 29 community, and requests discussion and suggestions for improvements. 30 Distribution of this draft is unlimited. 32 The protocol discussed in this document is experimental and subject 33 to change. Persons planning on either implementing or using this 34 protocol are STRONGLY URGED to get in touch with the author before 35 embarking on such a project. 37 1. Abstract 39 The Application Configuration Access Protocol [ACAP] defines rough 40 typing information in the form of an attribute naming convention. 41 This extension to ACAP allows a MIME content-type/subtype with 42 parameters to be associated with a given piece of data, providing 43 knowledgeable clients with useful information in a way which 44 maintains compatability with innocent clients and servers. 46 2. Conventions Used in this Document 48 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 49 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 50 document are to be interpreted as described in "Key words for use in 51 RFCs to Indicate Requirement Levels" [KEYWORDS]. 53 3. Specification 55 The TYPE extension may be used with any ACAP server which returns 56 "TYPE" as one of the supported capabilities in the initial untagged 57 ACAP response. 59 Servers that support the TYPE extension define a new type of metadata 60 on attributes, called "type". This metadatum is Read-Write, is 61 protected by the same ACL which protects the rest of the attribute, 62 and contains the MIME content-type/subtype of the "value" metadata 63 associated with the attribute, along with any associated parameters. 65 The "type" metadatum for an attribute MUST only be stored if the 66 "value" metadata are being set as well, in the same STORE command 67 (this is to deal effectively with inheritance; for example, it would 68 be bad if the "type" could be set in an inheriting attribute for an 69 inherited value, when the inherited value could change at a later 70 date. The value and the type of the value need to be considered 71 together, as a single unit). 73 Note that, in the case of a multivalued attribute, all of the values 74 are described by a single "type" metadatum, and thus MUST have the 75 same MIME content-type. 77 3.1. Client Issues 79 A client MAY request the "type" metadatum from any server which 80 supports the TYPE extension. This MUST NOT be taken as 81 authoritative; the associated "value" metadata might not in fact be 82 syntactically legal for the given type. Nevertheless, the type MAY 83 be used as a hint to indicate how the data should be treated or 84 displayed. 86 When a client stores a single or multi-value into the "value" 87 metadata of an attribute, it MAY, in addition, store a value into the 88 "type" metadatum of the attribute to indicate the type of the 89 associated "value" metadata. The type stored MUST be a legal MIME 90 type, and the "value" metadata MUST be legal values for that type. 92 If the client stores a NIL to the "value" metadata, it MUST either 93 store a NIL to the "type" metadatum, or omit the type information 94 from the STORE. 96 If the client stores a DEFAULT to the "value" metadata, it MUST 97 either store a DEFAULT to the "type" metadatum, or omit the type 98 information from the STORE. 100 If a server does not implement the TYPE extension, clients MUST NOT 101 assume anything about the type of the value associated with a given 102 attribute, or attempt to STORE to the "type" metadatum. 104 3.2. Server Issues 106 Servers implementing this extension SHOULD announce it via the 107 initial ACAP greeting, with the capability "TYPE". 109 Servers recieving a STORE command for a "type" metadatum MUST ensure 110 that the type is a legally formatted MIME type; if it is not, servers 111 MUST return a tagged BAD response. 113 If a client performs a STORE to the "type" metadatum of an attribute, 114 without simultaneously storing into the "value" metadata, the server 115 MUST return a tagged BAD response. 117 Servers MAY parse the "value" metadata and ensure that they conform 118 to the specified type; if they do not, a server MAY issue a tagged NO 119 response. 121 Servers MUST NOT reject STOREs to "type" metadatum merely because 122 they lack knowledge of the specific type, as long as the type is 123 correctly formatted. 125 If a server recieves a request to STORE a non-NIL or DEFAULT into the 126 "value" metadata of an attribute without an accompanying value for 127 the "type" metadatum, the server MUST behave as though the "type" 128 metadatum were being set to "application/octet-stream". 130 Note that this implies that the server MUST NOT reject a STORE into a 131 value that would be a legal store if this extension were not in place 132 -- a STORE without a supplied type MUST cause the type to change to 133 the most general type available given the restrictions imposed by the 134 base protocol on the types of data that a given attribute may assume. 136 If a server recieves a request to STORE a NIL to an attribute's 137 "value" metadata, the "type" MUST revert to NIL as well. If the 138 client STOREs NIL to the "value metadata, and explicitly specifies a 139 non-NIL value for the "type" metadatum, the server MUST issue a 140 tagged BAD response. 142 If a server recieves a request to STORE a DEFAULT to an attribute's 143 "value" metadata, the "type" MUST revert to DEFAULT as well. If the 144 client STOREs DEFAULT to the "value" metadata, and explicitly 145 specifies a non-DEFAULT value for the "type" metadatum, the server 146 MUST issue a tagged BAD response. 148 3.3. Examples 150 Example: C: A001 Store ("/user/rob/people/kelly" 151 "people.name" "Joe Kelly" 152 "people.description" ("value" "richtext" 153 "type" "text/enriched") 154 "people.icon.bin" ("value" {1024+} 155 "type" "image/png") 156 S: A001 OK "Store completed" 158 (where stands for the 1024 bytes of data that 159 make up the image/png object being stored). 161 4. Formal Syntax 163 The following syntax specification uses the augmented Backus-Naur 164 Form (BNF) notation as specified in [ABNF]. This uses the ABNF core 165 rules as specified in Appendix A of the ABNF specification [ABNF]. 167 Except as noted otherwise, all alphabetic characters are case- 168 insensitive. The use of upper or lower case characters to define 169 token strings is for editorial clarity only. Implementations MUST 170 accept these strings in a case-insensitive fashion. 172 "metadata-type" describes the format of the data which may be stored 173 as "type" metadatum. 175 metadata-type ::= type "/" subtype *(";" SPACE parameter) 176 ;; type, subtype, and parameter as defined in [MIME-IMB] 177 ;; free insertion of linear-white-space is not permitted. 179 5. Security Considerations 181 Clients SHOULD NOT automatically launch potentially unsafe helper 182 applications to view data. 184 6. Copyright 186 Copyright (C) The Internet Society 1998. All Rights Reserved. 188 This document and translations of it may be copied and furnished to 189 others, and derivative works that comment on or otherwise explain it 190 or assist in its implementation may be prepared, copied, published 191 and distributed, in whole or in part, without restriction of any 192 kind, provided that the above copyright notice and this paragraph are 193 included on all such copies and derivative works. However, this 194 document itself may not be modified in any way, such as by removing 195 the copyright notice or references to the Internet Society or other 196 Internet organizations, except as needed for the purpose of 197 developing Internet standards in which case the procedures for 198 copyrights defined in the Internet Standards process must be 199 followed, or as required to translate it into languages other than 200 English. 202 The limited permissions granted above are perpetual and will not be 203 revoked by the Internet Society or its successors or assigns. 205 This document and the information contained herein is provided on an 206 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 207 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 208 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 209 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 210 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 212 7. References 214 [ABNF] Crocker, D., and Overell, P., "Augmented BNF for Syntax 215 Specifications: ABNF", RFC 2234, November 1997. 217 219 [ACAP] Newman, C., and Myers, J., "Application Configuration Access 220 Protocol", RFC 2244, November 1997. 222 224 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate 225 Requirement Levels", BCP 14, RFC 2119, March 1997. 227 229 [MIME-IMB] Freed, N., and Borenstein, N., "Multipurpose Internet Mail 230 Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 231 2045, November 1996. 233 235 8. Author's Address 237 Robert H. Earhart 238 Carnegie Mellon 239 5000 Forbes Ave. 240 Pittsburgh PA, 15213-3890 242 Email: earhart+@cmu.edu 244 Expires September 1998