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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 2396 (Obsoleted by RFC 3986) ** Obsolete normative reference: RFC 2518 (Obsoleted by RFC 4918) ** Obsolete normative reference: RFC 2616 (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) -- Possible downref: Non-RFC (?) normative reference: ref. 'XML' Summary: 5 errors (**), 0 flaws (~~), 3 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Slein 3 Internet Draft Xerox 4 Expires: August 2003 J. Whitehead 5 U.C. Santa Cruz 6 J. Crawford 7 IBM 8 J. F. Reschke 9 greenbytes 10 February 2003 12 WebDAV Ordered Collections Protocol 13 draft-ietf-webdav-ordering-protocol-06 15 Status of this Memo 17 This document is an Internet-Draft and is in full conformance with 18 all provisions of Section 10 of RFC2026. Internet-Drafts are working 19 documents of the Internet Engineering Task Force (IETF), its areas, 20 and its working groups. Note that other groups may also distribute 21 working documents as Internet-Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress". 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire in August 2003. 36 Copyright Notice 38 Copyright (C) The Internet Society (2003). All Rights Reserved. 40 Abstract 42 This specification extends the WebDAV Distributed Authoring Protocol 43 to support server-side ordering of collection members. Of particular 44 interest are orderings that are not based on property values, and so 45 cannot be achieved using a search protocol's ordering option and 46 cannot be maintained automatically by the server. Protocol elements 47 are defined to let clients specify the position in the ordering of 48 each collection member, as well as the semantics governing the 49 ordering. 51 Distribution of this document is unlimited. Please send comments to 52 the Distributed Authoring and Versioning (WebDAV) working group at 53 w3c-dist-auth@w3.org, which may be joined by sending a message with 54 subject "subscribe" to w3c-dist-auth-request@w3.org. 56 Discussions of the WEBDAV working group are archived at URL: 57 http://lists.w3.org/Archives/Public/w3c-dist-auth/. 59 Table of Contents 61 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 62 Table of Contents . . . . . . . . . . . . . . . . . . . . . . 3 63 1 Notational Conventions . . . . . . . . . . . . . . . . . . . 5 64 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6 65 3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 7 66 4 Overview of Ordered Collections . . . . . . . . . . . . . . 8 67 4.1 Additional Collection properties . . . . . . . . . . . . 8 68 4.1.1 DAV:ordering-type (protected) . . . . . . . . . . . 9 69 5 Creating an Ordered Collection . . . . . . . . . . . . . . . 10 70 5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 10 71 5.2 Example: Creating an Ordered Collection . . . . . . . . 11 72 6 Setting the Position of a Collection Member . . . . . . . . 12 73 6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 74 6.2 Examples: Setting the Position of a Collection Member . 13 75 7 Changing a Collection Ordering: ORDERPATCH method . . . . . 15 76 7.1 Example: Changing a Collection Ordering . . . . . . . . 17 77 7.2 Example: Failure of an ORDERPATCH Request . . . . . . . 18 78 8 Listing the Members of an Ordered Collection . . . . . . . . 21 79 8.1 Example: PROPFIND on an Ordered Collection . . . . . . . 21 80 9 Relationship to versioned collections . . . . . . . . . . . 25 81 9.1 Collection Version Properties . . . . . . . . . . . . . 25 82 9.1.1 Additional semantics for DAV:version-controlled- 83 binding-set (protected) . . . . . . . . . . . . . . . . . . . 25 84 9.1.2 DAV:ordering-type (protected) . . . . . . . . . . . 25 85 9.2 Additional CHECKIN semantics . . . . . . . . . . . . . . 25 86 9.3 Additional CHECKOUT Semantics . . . . . . . . . . . . . 26 87 9.4 Additional UNCHECKOUT, UPDATE, and MERGE Semantics . . 26 88 10 Capability Discovery . . . . . . . . . . . . . . . . . . . 27 89 10.1 Example: Using OPTIONS for the Discovery of Support for 90 Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 91 10.2 Example: Using Live Properties for the Discovery of 92 Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 93 11 Security Considerations . . . . . . . . . . . . . . . . . . 30 94 11.1 Denial of Service and DAV:ordering-type . . . . . . . . 30 95 12 Internationalization Considerations . . . . . . . . . . . . 31 96 13 IANA Considerations . . . . . . . . . . . . . . . . . . . . 32 97 14 Copyright . . . . . . . . . . . . . . . . . . . . . . . . . 33 98 15 Intellectual Property . . . . . . . . . . . . . . . . . . . 34 99 16 Acknowledgements . . . . . . . . . . . . . . . . . . . . . 35 100 Normative References . . . . . . . . . . . . . . . . . . . . . 36 101 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 36 102 A Extensions to the WebDAV Document Type Definition . . . . . 38 103 B Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 39 104 B.1 Since draft-ietf-webdav-ordering-protocol dated December 105 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 106 B.2 Since draft-ietf-webdav-ordering-protocol-02 . . . . . . 39 107 B.3 Since draft-ietf-webdav-ordering-protocol-03 . . . . . . 39 108 B.4 Since draft-ietf-webdav-ordering-protocol-04 . . . . . . 40 109 B.5 Since draft-ietf-webdav-ordering-protocol-05 . . . . . . 40 110 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 112 1 Notational Conventions 114 Since this document describes a set of extensions to the WebDAV 115 Distributed Authoring Protocol [RFC2518], itself an extension to the 116 HTTP/1.1 protocol, the augmented BNF used here to describe protocol 117 elements is exactly the same as described in Section 2.1 of HTTP 118 [RFC2616]. Since this augmented BNF uses the basic production rules 119 provided in Section 2.2 of HTTP, these rules apply to this document 120 as well. 122 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 123 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 124 document are to be interpreted as described in [RFC2119]. 126 This document uses XML DTD fragments as a purely notational 127 convention. WebDAV request and response bodies can not be validated 128 due to the specific extensibility rules defined in section 23 of 129 [RFC2518] and due to the fact that all XML elements defined by this 130 specification use the XML namespace name "DAV:". In particular: 132 1. element names use the "DAV:" namespace, 134 2. element ordering is irrelevant, 136 3. extension elements (elements not already defined as valid child 137 elements) may be added anywhere, except when explicitly stated 138 otherwise, 140 4. extension attributes (attributes not already defined as valid for 141 this element) may be added anywhere, except when explicitly stated 142 otherwise. 144 2 Introduction 146 This specification builds on the collection infrastructure provided 147 by the WebDAV Distributed Authoring Protocol, adding support for the 148 server-side ordering of collection members. 150 There are many scenarios where it is useful to impose an ordering on 151 a collection at the server, such as expressing a recommended access 152 order, or a revision history order. The members of a collection might 153 represent the pages of a book, which need to be presented in order if 154 they are to make sense. Or an instructor might create a collection of 155 course readings, which she wants to be displayed in the order they 156 are to be read. 158 Orderings may be based on property values, but this is not always the 159 case. The resources in the collection may not have properties that 160 can be used to support the desired ordering. Orderings based on 161 properties can be obtained using a search protocol's ordering option, 162 but orderings not based on properties cannot. These orderings 163 generally need to be maintained by a human user. 165 The ordering protocol defined here focuses on support for such human- 166 maintained orderings. Its protocol elements allow clients to specify 167 the position of each collection member in the collection's ordering, 168 as well as the semantics governing the ordering. The protocol is 169 designed to allow support to be added in the future for orderings 170 that are maintained automatically by the server. 172 The remainder of this document is structured as follows: section 3 173 defines terminology that will be used throughout the specification. 174 Section 4 provides an overview of ordered collections. Section 5 175 describes how to create an ordered collection, and section 6 176 discusses how to set a member's position in the ordering of a 177 collection. Section 7 explains how to change a collection ordering. 178 Section 8 discusses listing the members of an ordered collection. 179 Section 9 discusses the impact on version-controlled collections (as 180 defined in [RFC3253]. Section 10 describes capability discovery. 181 Section 11 through section 13 discuss security, internationalization, 182 and IANA considerations. The remaining sections provide supporting 183 information. 185 3 Terminology 187 The terminology used here follows that in [RFC2518] and [RFC3253]. 188 Definitions of the terms resource, Uniform Resource Identifier (URI), 189 and Uniform Resource Locator (URL) are provided in [RFC2396]. 191 Ordered Collection 193 A collection for which the results from a PROPFIND request are 194 guaranteed to be in the order specified for that collection 196 Unordered Collection 198 A collection for which the client cannot depend on the 199 repeatability of the ordering of results from a PROPFIND request 201 Client-Maintained Ordering 203 An ordering of collection members that is maintained on the server 204 based on client requests specifying the position of each 205 collection member in the ordering 207 Server-Maintained Ordering 209 An ordering of collection members that is maintained automatically 210 by the server, based on a client's choice of ordering semantics 212 This document uses the terms "precondition", "postcondition" and 213 "protected property" as defined in [RFC3253]. Servers MUST report 214 pre-/postcondition failures as described in section 1.6 of this 215 document. 217 4 Overview of Ordered Collections 219 If a collection is unordered, the client cannot depend on the 220 repeatability of the ordering of results from a PROPFIND request. By 221 specifying an ordering for a collection, a client requires the server 222 to follow that ordering whenever it responds to a PROPFIND request on 223 that collection. 225 Server-side orderings may be client-maintained or server-maintained. 226 For client-maintained orderings, a client must specify the ordering 227 position of each of the collection's members, either when the member 228 is added to the collection (using the Position header) or later 229 (using the ORDERPATCH method). For server-maintained orderings, the 230 server automatically positions each of the collection's members 231 according to the ordering semantics. This specification supports only 232 client-maintained orderings, but is designed to allow future 233 extension to server-maintained orderings. 235 A collection that supports ordering is not required to be ordered. 237 If a collection is ordered, each of its internal member URIs MUST be 238 in the ordering exactly once, and the ordering MUST NOT include any 239 URI that is not an internal member of the collection. The server is 240 responsible for enforcing these constraints on orderings. The server 241 MUST remove an internal member URI from the ordering when it is 242 removed from the collection. The server MUST add an internal member 243 URI to the ordering when it is added to the collection. 245 Only one ordering can be attached to any collection. Multiple 246 orderings of the same resources can be achieved by creating multiple 247 collections referencing those resources, and attaching a different 248 ordering to each collection. 250 An ordering is considered to be part of the state of a collection 251 resource. Consequently, the ordering is the same no matter which URI 252 is used to access the collection and is protected by locks or access 253 control constraints on the collection. 255 4.1 Additional Collection properties 257 A DAV:allprop PROPFIND request SHOULD NOT return any of the 258 properties defined in this document. 260 4.1.1 DAV:ordering-type (protected) 262 Indicates whether the collection is ordered and, if so, uniquely 263 identifies the semantics of the ordering being used. May also point 264 to an explanation of the semantics in human and / or machine-readable 265 form. At a minimum, this allows human users who add members to the 266 collection to understand where to position them in the ordering. This 267 property cannot be set using PROPPATCH. Its value can only be set by 268 including the Ordering-Type header with a MKCOL request or by 269 submitting an ORDERPATCH request. 271 Ordering types are identified by URIs that uniquely identify the 272 semantics of the collection's ordering. The following two URIs are 273 predefined: 275 DAV:custom The value DAV:custom indicates that the collection is 276 ordered, but the semantics governing the ordering are 277 not being advertised. 278 DAV:unordered The value DAV:unordered indicates that the collection 279 is not ordered. That is, the client cannot depend on 280 the repeatability of the ordering of results from a 281 PROPFIND request. 283 An ordering-aware client interacting with an ordering-unaware server 284 (e.g., one that is implemented only according to [RFC2518]) SHOULD 285 assume that if a collection does not have the DAV:ordering-type 286 property, the collection is unordered. 288 290 5 Creating an Ordered Collection 292 5.1 Overview 294 When a collection is created, the client MAY request that it be 295 ordered and specify the semantics of the ordering by using the new 296 Ordering-Type header (defined below) with a MKCOL request. 298 For collections that are ordered, the client SHOULD identify the 299 semantics of the ordering with a URI in the Ordering-Type header, 300 although the client MAY simply set the header value to DAV:custom to 301 indicate that the collection is ordered but the semantics of the 302 ordering are not being advertised. Setting the value to a URI that 303 identifies the ordering semantics provides the information a human 304 user or software package needs to insert new collection members into 305 the ordering intelligently. Although the URI in the Ordering-Type 306 header MAY point to a resource that contains a definition of the 307 semantics of the ordering, clients SHOULD NOT access that resource, 308 in order to avoid overburdening its server. A value of DAV:unordered 309 in the Ordering-Type header indicates that the client wants the 310 collection to be unordered. If the Ordering-Type header is not 311 present, the collection will be unordered. 313 Additional Marshalling: 315 Ordering-Type = "Ordering-Type" ":" absoluteURI 316 ; absoluteURI: see RFC2396, section 3 318 The URI "DAV:unordered" indicates that the collection is not 319 ordered, while "DAV:custom" indicates that the collection is to be 320 ordered, but the semantics of the ordering is not being 321 advertised. Any other URI value indicates that the collection is 322 ordered, and identifies the semantics of the ordering. 324 Additional Preconditions: 326 (DAV:ordered-collections-supported): the server MUST support 327 ordered collections in the part of the URL namespace identified by 328 the request URL. 330 Additional Postconditions: 332 (DAV:ordering-type-set): if the Ordering-Type header was present, 333 the request MUST have created a new collection resource with the 334 DAV:ordering-type being set according to the Ordering-Type request 335 header. The collection MUST be ordered unless the ordering type 336 was "DAV:unordered". 338 5.2 Example: Creating an Ordered Collection 340 >> Request: 342 MKCOL /theNorth/ HTTP/1.1 343 Host: example.org 344 Ordering-Type: http://example.org/orderings/compass.html 346 >> Response: 348 HTTP/1.1 201 Created 350 In this example a new, ordered collection was created. Its 351 DAV:ordering-type property has as its value the URI from the 352 Ordering-Type header, http://example.org/orderings/compass.html. In 353 this case, the URI identifies the semantics governing a client- 354 maintained ordering. As new members are added to the collection, 355 clients or end users can use the semantics to determine where to 356 position the new members in the ordering. 358 6 Setting the Position of a Collection Member 360 6.1 Overview 362 When a new member is added to a collection with a client-maintained 363 ordering (for example, with PUT, COPY, or MKCOL), its position in the 364 ordering can be set with the new Position header. The Position header 365 allows the client to specify that an internal member URI should be 366 first in the collection's ordering, last in the collection's 367 ordering, immediately before some other internal member URI in the 368 collection's ordering, or immediately after some other internal 369 member URI in the collection's ordering. 371 If the Position request header is not used when adding a member to an 372 ordered collection, then: 374 o If the request is replacing an existing resource, the server MUST 375 preserve the present ordering. 377 o If the request is adding a new internal member URI to the 378 collection, the server MUST append the new member to the end of 379 the ordering. 381 Additional Marshalling: 383 Position = "Position" ":" ("first" | "last" | 384 (("before" | "after") segment)) 386 segment is defined in Section 3.3 of [RFC2396]. 388 The segment is interpreted relative to the collection to which the 389 new member is being added. 391 When the Position header is present, the server MUST insert the 392 new member into the ordering at the specified location. 394 The "first" keyword indicates the new member is put in the 395 beginning position in the collection's ordering, while "last" 396 indicates the new member is put in the final position in the 397 collection's ordering. The "before" keyword indicates the new 398 member is added to the collection's ordering immediately prior to 399 the position of the member identified in the segment. Likewise, 400 the "after" keyword indicates the new member is added to the 401 collection's ordering immediately following the position of the 402 member identified in the segment. 404 If the request is replacing an existing resource, and the Position 405 header is present, the server MUST remove the internal member URI 406 from its previous position, and then insert it at the requested 407 position. 409 Additional Preconditions: 411 (DAV:collection-must-be-ordered): the target collection MUST be 412 ordered. 414 (DAV:segment-must-identify-member): the referenced segment MUST 415 identify a resource that exists and is different from the affected 416 resource. 418 Additional Postconditions: 420 (DAV:position-set): if a Position header was present, the request 421 MUST have created the new collection member at the specified 422 position. 424 6.2 Examples: Setting the Position of a Collection Member 426 >> Request: 428 COPY /~user/dav/spec08.html HTTP/1.1 429 Host: example.org 430 Destination: http://example.org/~slein/dav/spec08.html 431 Position: after requirements.html 433 >> Response: 435 HTTP/1.1 201 Created 436 This request resulted in the creation of a new resource at 437 example.org/~slein/dav/spec08.html. The Position header in this 438 example caused the server to set its position in the ordering of the 439 /~slein/dav/ collection immediately after requirements.html. 441 >> Request: 443 MOVE /i-d/draft-webdav-prot-08.txt HTTP/1.1 444 Host: example.org 445 Destination: http://example.org/~user/dav/draft-webdav-prot-08.txt 446 Position: first 448 >> Response: 450 HTTP/1.1 409 Conflict 451 Content-Type: text/xml; charset="utf-8" 452 Content-Length: xxxx 454 455 456 457 459 In this case, the server returned a 409 (Conflict) status code 460 because the /~user/dav/ collection is an unordered collection. 461 Consequently, the server was unable to satisfy the Position header. 463 7 Changing a Collection Ordering: ORDERPATCH method 465 The ORDERPATCH method is used to change the ordering semantics of a 466 collection or to change the order of the collection's members in the 467 ordering or both. 469 The server MUST apply the changes in the order they appear in the 470 order XML element. The server MUST either apply all the changes or 471 apply none of them. If any error occurs during processing, all 472 executed changes MUST be undone and a proper error result returned. 474 If an ORDERPATCH request changes the ordering semantics, but does not 475 completely specify the order of the collection members, the server 476 MUST assign a position in the ordering to each collection member for 477 which a position was not specified. These server-assigned positions 478 MUST all follow the last one specified by the client. The result is 479 that all members for which the client specified a position are at the 480 beginning of the ordering, followed by any members for which the 481 server assigned positions. 483 If an ORDERPATCH request does not change the ordering semantics, any 484 member positions not specified in the request MUST remain unchanged. 486 A request to reposition a collection member at the same place in the 487 ordering is not an error. 489 Additional Marshalling: 491 The request body MUST be DAV:orderpatch element. 493 495 496 497 498 499 500 501 503 PCDATA value: segment, as defined in section 3.3 of [RFC2396]. 505 The DAV:ordering-type property is modified according to the 506 DAV:ordering-type element. 508 The ordering of internal member URIs in the collection identified 509 by the Request-URI is changed based on instructions in the order- 510 member XML elements in the order they appear in the request. The 511 order-member XML elements identify the internal member URIs whose 512 positions are to be changed, and describe their new positions in 513 the ordering. Each new position can be specified as first in the 514 ordering, last in the ordering, immediately before some other 515 internal member URI, or immediately after some other internal 516 member URI. 518 If a response body for a successful request is included, it MUST 519 be a DAV:orderpatch-response XML element. Note that this document 520 does not define any elements for the ORDERPATCH response body, but 521 the DAV:orderpatch-response element is defined to ensure 522 interoperability between future extensions that do define elements 523 for the ORDERPATCH response body. 525 527 Since multiple changes can be requested in a single ORDERPATCH 528 request, if any problems are encountered, the server MUST return a 529 207 (Multi-Status) response (defined in [RFC2518]), containing 530 DAV:response elements for either the request-URI (when the 531 DAV:ordering-type could not be modified) or URIs of collection 532 members to be repositioned (when an individual positioning request 533 expressed as DAV:order-member could not be fulfilled). 535 Preconditions: 537 (DAV:collection-must-be-ordered): see section 6.1. 539 (DAV:segment-must-identify-member): see section 6.1. 541 Postconditions: 543 (DAV:ordering-type-set): if the request body contained a 544 DAV:ordering-type element, the request MUST have set the 545 DAV:ordering-type property of the collection to the value 546 specified in the request. 548 (DAV:ordering-modified): if the request body contained DAV:order- 549 member elements, the request MUST have set the ordering of 550 internal member URIs in the collection identified by the request- 551 URI based on the instructions in the DAV:order-member elements. 553 7.1 Example: Changing a Collection Ordering 555 Consider a collection /coll-1/ whose DAV:ordering-type is DAV:whim, 556 with bindings ordered as follows: 558 three.html 559 four.html 560 one.html 561 two.html 563 >> Request: 565 ORDERPATCH /coll-1/ HTTP/1.1 566 Host: example.org 567 Content-Type: text/xml; charset="utf-8" 568 Content-Length: xxx 570 571 572 573 http://example.org/inorder.ord 574 575 576 two.html 577 578 579 580 one.html 581 582 583 584 three.html 585 586 587 588 four.html 589 590 591 593 >> Response: 595 HTTP/1.1 200 OK 597 In this example, after the request has been processed, the 598 collection's ordering semantics are identified by the URI 599 http://example.org/inorder.ord. The value of the collection's 600 DAV:ordering-type property has been set to this URI. The request also 601 contains instructions for changing the positions of the collection's 602 internal member URIs in the ordering to comply with the new ordering 603 semantics. As the DAV:order-member elements are required to be 604 processed in the order they appear in the request, two.html is moved 605 to the beginning of the ordering, and then one.html is moved to the 606 beginning of the ordering. Then three.html is moved to the end of the 607 ordering, and finally four.html is moved to the end of the ordering. 608 After the request has been processed, the collection's ordering is as 609 follows: 611 one.html 612 two.html 613 three.html 614 four.html 616 7.2 Example: Failure of an ORDERPATCH Request 618 Consider a collection /coll-1/ with members ordered as follows: 620 nunavut.map 621 nunavut.img 622 baffin.map 623 baffin.desc 624 baffin.img 625 iqaluit.map 626 nunavut.desc 627 iqaluit.img 628 iqaluit.desc 630 >> Request: 632 ORDERPATCH /coll-1/ HTTP/1.1 633 Host: www.nunanet.com 634 Content-Type: text/xml; charset="utf-8" 635 Content-Length: xxx 637 638 639 640 nunavut.desc 641 642 643 nunavut.map 644 645 646 647 648 iqaluit.map 649 650 651 pangnirtung.img 652 653 654 655 657 >> Response: 659 HTTP/1.1 207 Multi-Status 660 Content-Type: text/xml; charset="utf-8" 661 Content-Length: xxx 662 663 664 665 http://www.nunanet.com/coll-1/iqaluit.map 666 HTTP/1.1 403 Forbidden 667 668 669 pangnirtung.img is not a collection member. 670 671 672 674 In this example, the client attempted to position iqaluit.map after a 675 URI that is not an internal member of the collection /coll-1/. The 676 server responded to this client error with a 403 (Forbidden) status 677 code, indicating the failed precondition DAV:segment-must-identify- 678 member. Because ORDERPATCH is an atomic method, the request to 679 reposition nunavut.desc (which would otherwise have succeeded) failed 680 as well, but doesn't need to be expressed in the multistatus response 681 body. 683 8 Listing the Members of an Ordered Collection 685 A PROPFIND request is used to retrieve a listing of the members of an 686 ordered collection, just as it is used to retrieve a listing of the 687 members of an unordered collection. 689 However, when responding to a PROPFIND on an ordered collection, the 690 server MUST order the response elements according to the ordering 691 defined on the collection. If a collection is unordered, the client 692 cannot depend on the repeatability of the ordering of results from a 693 PROPFIND request. 695 In a response to a PROPFIND with Depth: infinity, members of 696 different collections may be interleaved. That is, the server is not 697 required to do a breadth-first traversal. The only requirement is 698 that the members of any ordered collection appear in the order 699 defined for the collection. Thus for the hierarchy illustrated in the 700 following figure, where collection A is an ordered collection with 701 the ordering B C D, 703 A 704 /|\ 705 / | \ 706 B C D 707 / /|\ 708 E F G H 710 it would be acceptable for the server to return response elements in 711 the order A B E C F G H D. In this response, B, C, and D appear in 712 the correct order, separated by members of other collections. Clients 713 can use a series of Depth: 1 PROPFIND requests to avoid the 714 complexity of processing Depth: infinity responses based on depth- 715 first traversals. 717 8.1 Example: PROPFIND on an Ordered Collection 719 Suppose a PROPFIND request is submitted to /MyColl/, which has its 720 members ordered as follows. 722 /MyColl/ 723 lakehazen.html 724 siorapaluk.html 725 iqaluit.html 726 newyork.html 728 >> Request: 730 PROPFIND /MyColl/ HTTP/1.1 731 Host: example.org 732 Depth: 1 733 Content-Type: text/xml; charset="utf-8" 734 Content-Length: xxxx 736 737 738 739 740 741 742 743 745 >> Response: 747 HTTP/1.1 207 Multi-Status 748 Content-Type: text/xml; charset="utf-8" 749 Content-Length: xxxx 751 752 754 755 http://example.org/MyColl/ 756 757 758 759 DAV:custom 760 761 762 763 HTTP/1.1 200 OK 765 766 767 768 769 770 HTTP/1.1 404 Not Found 771 772 773 774 http://example.org/MyColl/lakehazen.html 775 776 777 778 82N 779 780 HTTP/1.1 200 OK 781 782 783 784 785 786 HTTP/1.1 404 Not Found 787 788 789 790 http://example.org/MyColl/siorapaluk.html 792 793 794 795 78N 796 797 HTTP/1.1 200 OK 798 799 800 801 802 803 HTTP/1.1 404 Not Found 804 805 806 807 http://example.org/MyColl/iqaluit.html 808 809 810 811 62N 812 813 HTTP/1.1 200 OK 814 815 816 817 818 819 HTTP/1.1 404 Not Found 820 821 822 823 http://example.org/MyColl/newyork.html 824 825 826 827 45N 828 829 HTTP/1.1 200 OK 830 831 832 833 834 HTTP/1.1 404 Not Found 835 836 837 838 840 In this example, the server responded with a list of the collection 841 members in the order defined for the collection. 843 9 Relationship to versioned collections 845 The Versioning Extensions to WebDAV [RFC3253] introduce the concept 846 of versioned collections, recording both the dead properties and the 847 set of internal version-controlled bindings. This section defines how 848 this feature interacts with ordered collections. 850 This specification considers both the ordering type (DAV:ordering- 851 type property) and the ordering of collection members to be part of 852 the state of a collection. Therefore both MUST be recorded upon 853 CHECKIN or VERSION-CONTROL, and both MUST be restored upon CHECKOUT, 854 UNCHECKOUT or UPDATE (where for compatibility with RFC3253, only the 855 ordering of version-controlled members needs to be maintained). 857 9.1 Collection Version Properties 859 9.1.1 Additional semantics for DAV:version-controlled-binding-set 860 (protected) 862 For ordered collections, the DAV:version-controlled-binding elements 863 MUST appear in the ordering defined for the checked-in ordered 864 collection. 866 9.1.2 DAV:ordering-type (protected) 868 The DAV:ordering-type property records the DAV:ordering-type property 869 of the checked-in ordered collection. 871 9.2 Additional CHECKIN semantics 873 Additional Postconditions: 875 (DAV:initialize-version-controlled-bindings-ordered): If the 876 request-URL identified a both ordered and version-controlled 877 collection, then the child elements of DAV:version-controlled- 878 binding-set of the new collection version MUST appear in the 879 ordering defined for that collection. 881 (DAV:initialize-collection-version-ordering-type): If the request- 882 URL identified a both ordered and version-controlled collection, 883 then the DAV:ordering-type property of the new collection version 884 MUST be a copy of the collection's DAV:ordering-type property. 886 9.3 Additional CHECKOUT Semantics 888 Additional Postconditions: 890 (DAV:initialize-version-history-bindings-ordered): If the request 891 has been applied to a collection version with a DAV:ordering-type 892 other than "DAV:unordered", the bindings in the new working 893 collection MUST be ordered according to the collection version's 894 DAV:version-controlled-binding-set property. 896 (DAV:initialize-ordering-type): If the request has been applied to 897 a collection version, the DAV:ordering-type property of the new 898 working collection MUST be initialized from the collection 899 version's DAV:ordering-type property. 901 9.4 Additional UNCHECKOUT, UPDATE, and MERGE Semantics 903 Additional Postconditions: 905 (DAV:update-version-controlled-collection-members-ordered): If the 906 request modified the DAV:checked-in version of a version- 907 controlled collection and the DAV:ordering-type for the checked-in 908 version is not unordered ("DAV:unordered"), the version-controlled 909 members MUST be ordered according to the checked-in version's 910 DAV:version-controlled-binding-set property. 912 (DAV:update-version-ordering-type): If the request modified the 913 DAV:checked-in version of a version-controlled collection, the 914 DAV:ordering-type property MUST be updated from the checked-in 915 version's property. 917 10 Capability Discovery 919 Sections 9.1 and 15 of [RFC2518] describe the use of compliance 920 classes with the DAV header in responses to OPTIONS, to indicate 921 which parts of the Web Distributed Authoring protocols the resource 922 supports. This specification defines an OPTIONAL extension to 923 [RFC2518]. It defines a new compliance class, called ordered- 924 collections, for use with the DAV header in responses to OPTIONS 925 requests. If a collection resource does support ordering, its 926 response to an OPTIONS request may indicate that it does, by listing 927 the new ORDERPATCH method as one it supports, and by listing the new 928 ordered-collections compliance class in the DAV header. 930 When responding to an OPTIONS request, only a collection or a null 931 resource can include ordered-collections in the value of the DAV 932 header. By including ordered-collections, the resource indicates that 933 its internal member URIs can be ordered. It implies nothing about 934 whether any collections identified by its internal member URIs can be 935 ordered. 937 Furthermore, RFC 3253 [RFC3253] introduces the live properties 938 DAV:supported-method-set (section 3.1.3) and DAV:supported-live- 939 property-set (section 3.1.4). Servers MUST support these properties 940 as defined in RFC 3253. 942 10.1 Example: Using OPTIONS for the Discovery of Support for Ordering 944 >> Request: 946 OPTIONS /somecollection/ HTTP/1.1 947 Host: example.org 949 >> Response: 951 HTTP/1.1 200 OK 952 Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE 953 Allow: MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, ORDERPATCH 954 DAV: 1, 2, ordered-collections 956 The DAV header in the response indicates that the resource 957 /somecollection/ is level 1 and level 2 compliant, as defined in 959 [RFC2518]. In addition, /somecollection/ supports ordering. The Allow 960 header indicates that ORDERPATCH requests can be submitted to 961 /somecollection/. 963 10.2 Example: Using Live Properties for the Discovery of Ordering 965 >> Request: 967 PROPFIND /somecollection HTTP/1.1 968 Depth: 0 969 Content-Type: text/xml; charset="utf-8" 970 Content-Length: xxx 972 973 974 975 976 977 978 980 >> Response: 982 HTTP/1.1 207 Multi-Status 983 Content-Type: text/xml; charset="utf-8" 984 Content-Length: xxx 986 987 988 989 http://example.org/somecollection 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 HTTP/1.1 200 OK 1017 1018 1019 1021 Note that actual responses MUST contain a complete list of supported 1022 live properties. 1024 11 Security Considerations 1026 This section is provided to make WebDAV applications aware of the 1027 security implications of this protocol. 1029 All of the security considerations of HTTP/1.1 and the WebDAV 1030 Distributed Authoring Protocol specification also apply to this 1031 protocol specification. In addition, ordered collections introduce a 1032 new security concern. This issue is detailed here. 1034 11.1 Denial of Service and DAV:ordering-type 1036 There may be some risk of denial of service at sites that are 1037 advertised in the DAV:ordering-type property of collections. However, 1038 it is anticipated that widely-deployed applications will use hard- 1039 coded values for frequently-used ordering semantics rather than 1040 looking up the semantics at the location specified by DAV:ordering- 1041 type. This risk will be further reduced if clients observe the 1042 recommendation of section 5.1 that they not send requests to the URI 1043 in DAV:ordering-type. 1045 12 Internationalization Considerations 1047 This specification follows the practices of [RFC2518] in encoding all 1048 human-readable content using [XML] and in the treatment of names. 1049 Consequently, this specification complies with the IETF Character Set 1050 Policy [RFC2277]. 1052 WebDAV applications MUST support the character set tagging, character 1053 set encoding, and the language tagging functionality of the XML 1054 specification. This constraint ensures that the human-readable 1055 content of this specification complies with [RFC2277]. 1057 As in [RFC2518], names in this specification fall into three 1058 categories: names of protocol elements such as methods and headers, 1059 names of XML elements, and names of properties. Naming of protocol 1060 elements follows the precedent of HTTP, using English names encoded 1061 in USASCII for methods and headers. The names of XML elements used in 1062 this specification are English names encoded in UTF-8. 1064 For error reporting, [RFC2518] follows the convention of HTTP/1.1 1065 status codes, including with each status code a short, English 1066 description of the code (e.g., 423 Locked). Internationalized 1067 applications will ignore this message, and display an appropriate 1068 message in the user's language and character set. 1070 This specification introduces no new strings that are displayed to 1071 users as part of normal, error-free operation of the protocol. 1073 For rationales for these decisions and advice for application 1074 implementors, see [RFC2518]. 1076 13 IANA Considerations 1078 This document uses the namespaces defined by [RFC2518] for properties 1079 and XML elements. All other IANA considerations mentioned in 1080 [RFC2518] also apply to this document. 1082 14 Copyright 1084 To be supplied by the RFC Editor. 1086 15 Intellectual Property 1088 To be supplied by the RFC Editor. 1090 16 Acknowledgements 1092 This draft has benefited from thoughtful discussion by Jim Amsden, 1093 Steve Carter, Tyson Chihaya, Geoff Clemm, Ken Coar, Ellis Cohen, 1094 Bruce Cragun, Jim Davis, Spencer Dawkins, Mark Day, Rajiv Dulepet, 1095 David Durand, Lisa Dusseault, Chuck Fay, Roy Fielding, Yaron Goland, 1096 Fred Hitt, Alex Hopmann, Marcus Jager, Chris Kaler, Manoj 1097 Kasichainula, Rohit Khare, Daniel LaLiberte, Steve Martin, Larry 1098 Masinter, Jeff McAffer, Surendra Koduru Reddy, Max Rible, Sam Ruby, 1099 Bradley Sergeant, Nick Shelness, John Stracke, John Tigue, John 1100 Turner, Kevin Wiggen, and others. 1102 Normative References 1104 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1105 Requirement Levels", BCP 14, RFC 2119, March 1997. 1107 [RFC2277] Alvestrand, H.T., "IETF Policy on Character Sets and 1108 Languages", BCP 18, RFC 2277, January 1998. 1110 [RFC2396] Berners-Lee, T., Fielding, R.T. and Masinter, L., "Uniform 1111 Resource Identifiers (URI): Generic Syntax", RFC 2396, 1112 August 1998. 1114 [RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S.R. and 1115 Jensen, D., "HTTP Extensions for Distributed Authoring -- 1116 WEBDAV", RFC 2518, February 1999. 1118 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1119 Masinter, L., Leach, P. and Berners-Lee, T., "Hypertext 1120 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1122 [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and 1123 Whitehead, J., "Versioning Extensions to WebDAV", RFC 1124 3253, March 2002. 1126 [XML] Bray, T., Paoli, J., Sperberg-McQueen, C.M. and Maler, E., 1127 "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC- 1128 xml, October 2000. 1130 Author's Addresses 1132 Judith Slein 1133 Xerox Corporation 1134 800 Phillips Road, 105-50C 1135 Webster, NY 14580 1137 EMail: jslein@crt.xerox.com 1139 Jim Whitehead 1140 UC Santa Cruz, Dept. of Computer Science 1141 1156 High Street 1142 Santa Cruz, CA 95064 1143 US 1145 EMail: ejw@cse.ucsc.edu 1146 Jason Crawford 1147 IBM Research 1148 P.O. Box 704 1149 Yorktown Heights, NY 10598 1151 EMail: ccjason@us.ibm.com 1153 Julian F. Reschke 1154 greenbytes GmbH 1155 Salzmannstrasse 152 1156 Muenster, NW 48159 1157 Germany 1159 Phone: +49 251 2807760 1160 Fax: +49 251 2807761 1161 EMail: julian.reschke@greenbytes.de 1162 URI: http://greenbytes.de/tech/webdav/ 1164 A Extensions to the WebDAV Document Type Definition 1166 1167 1168 1169 1170 1171 1172 1173 1174 1176 B Change Log 1178 B.1 Since draft-ietf-webdav-ordering-protocol dated December 1999 1180 Updated contact information for all previous authors. 1181 Specify charset when using text/xml media type. 1182 Made sure artwork fits into 72 columns. 1183 Removed "Public" header from OPTIONS example. 1184 Added Julian Reschke to list of authors. 1185 Fixed broken XML in PROPFIND example and added DAV:orderingtype to 1186 list of requested properties. 1187 Added support for DAV:supported-live-property-set and DAV:supported- 1188 method-set as mandatory features. 1190 B.2 Since draft-ietf-webdav-ordering-protocol-02 1192 Updated change log to refer to expired draft version as "December 1193 1999" version. 1194 Started rewrite marshalling in RFC3253-style and added precondition 1195 and postcondition definitions. 1196 On his request, removed Geoff Clemm's name from the author list 1197 (moved to Acknowledgments). 1198 Renamed "References" to "Normative References". 1199 Removed reference to "MKREF" method. 1201 B.3 Since draft-ietf-webdav-ordering-protocol-03 1203 Added a set of issues regarding marshalling. 1204 Changed host names to use proper "example" domain names (no change 1205 tracking). Fixed host/destination header conflicts. Fixed "allow" 1206 header (multiline). Removed irrelevant response headers. Abbreviated 1207 some URIs (no change tracking). 1208 Removed Jim Davis and Chuck Fay from the author list (and added them 1209 to the Acknowledgements section). 1210 Updated section on setting the position when adding new members, 1211 removed old section on Position header. 1212 Started work on Index section. 1213 Changed structure for section 7 (no change tracking). 1214 Removed header and XML elements section (contents moved to other 1215 sections). 1216 Started new section on relation to versioned collections as per 1217 RFC3253. 1218 Do not return 424's for in ORDERPATCH multistatus (it's atomic 1219 anyway). 1221 B.4 Since draft-ietf-webdav-ordering-protocol-04 1223 Added proper reference to definition of "Coded-URL". 1224 Closed issue ordering-type-values (content model simplified and XML 1225 element / DAV property renamed) and updated examples. 1226 Renamed precondition DAV:orderingtype-set to DAV:ordering-type-set 1227 (no change tracking). 1228 Closed issue ordered-header-name (header name changed to "ordering- 1229 type", contents matches live property). 1230 Closed issue ordermember-format (now takes segment instead of href). 1231 Renamed compliance class to "ordered-collections" for consistency 1232 with newer specs, and to allow detection of compliance to final 1233 version of spec. 1234 Updated reference to XML spec to 1.0, 2nd edition. 1236 B.5 Since draft-ietf-webdav-ordering-protocol-05 1238 Typos fixed. 1239 Renamed DAV:ordermember to DAV:order-member. 1240 Made RFC3253-compatible pre/postcondition handling a MUST 1241 requirement. 1242 Reference definition of "protected property" from RFC3253. 1243 Added explanation of role of DTD fragments to Notation section. 1244 Clarified semantics for operations on versioned collections and 1245 collection versions. 1247 Index 1249 C 1251 Client-Maintained Ordering 1252 3 1254 D 1256 DAV:collection-must-be-ordered precondition 1257 6.1 1258 DAV:custom ordering type 1259 4.1.1 1260 DAV:initialize-collection-version-ordering-type 1261 9.2 1262 DAV:initialize-ordering-type 1263 9.3 1264 DAV:initialize-version-controlled-bindings-ordered postcondition 1265 9.2 1266 DAV:initialize-version-history-bindings-ordered 1267 9.3 1268 DAV:ordered-collections-supported precondition 1269 5.1 1270 DAV:ordering-modified postcondition 1271 7 1272 DAV:ordering-type property 1273 4.1.1 1274 DAV:ordering-type-set postcondition 1275 5.1, 7 1276 DAV:position-set postcondition 1277 6.1 1278 DAV:segment-must-identify-member precondition 1279 6.1 1280 DAV:unordered ordering type 1281 4.1.1 1282 DAV:update-version-controlled-collection-members-ordered 1283 9.4 1284 DAV:update-version-ordering-type 1285 9.4 1287 H 1289 Headers 1290 Ordering-Type 5.1 1292 O 1294 Ordered Collection 1295 3 1296 Ordering-Type header 1297 5.1 1298 ORDERPATCH method 1299 7 1301 P 1303 Postconditions 1304 DAV:ordering-type-set 5.1, 7 1305 DAV:position-set 6.1 1306 DAV:ordering-type-set 5.1, 7 1307 DAV:ordering-modified 7 1308 DAV:initialize-version-controlled-bindings-ordered 9.2 1309 DAV:initialize-collection-version-ordering-type 9.2 1310 DAV:initialize-version-history-bindings-ordered 9.3 1311 DAV:initialize-ordering-type 9.3 1312 DAV:update-version-controlled-collection-members-ordered 9.4 1313 DAV:update-version-ordering-type 9.4 1315 Preconditions 1316 DAV:ordered-collections-supported 5.1 1317 DAV:collection-must-be-ordered 6.1 1318 DAV:segment-must-identify-member 6.1 1320 Protected properties 1321 DAV:ordering-type 4.1.1 1323 S 1325 Server-Maintained Ordering 1326 3 1328 U 1330 Unordered Collection 1331 3 1333 Full Copyright Statement 1335 Copyright (C) The Internet Society (2003). All Rights Reserved. 1337 This document and translations of it may be copied and furnished 1338 to others, and derivative works that comment on or otherwise 1339 explain it or assist in its implementation may be prepared, 1340 copied, published and distributed, in whole or in part, without 1341 restriction of any kind, provided that the above copyright notice 1342 and this paragraph are included on all such copies and derivative 1343 works. 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