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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 5988 (Obsoleted by RFC 8288) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Douglass 3 Internet-Draft Spherical Cow Group 4 Updates: 5545 (if approved) October 11, 2017 5 Intended status: Standards Track 6 Expires: April 14, 2018 8 Support for iCalendar Relationships 9 draft-ietf-calext-ical-relations-03 11 Abstract 13 This specification updates RELATED-TO defined in [RFC5545] and 14 introduces new iCalendar properties LINK, CONCEPT and REFID to allow 15 better linking and grouping of iCalendar components and related data. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on April 14, 2018. 34 Copyright Notice 36 Copyright (c) 2017 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 1.1. Structured iCalendar relationships . . . . . . . . . . . 3 53 1.2. Grouped iCalendar relationships . . . . . . . . . . . . . 3 54 1.3. Concept relationships . . . . . . . . . . . . . . . . . . 3 55 1.4. Linked relationships . . . . . . . . . . . . . . . . . . 4 56 1.5. Caching and offline use . . . . . . . . . . . . . . . . . 5 57 1.6. Conventions Used in This Document . . . . . . . . . . . . 5 58 2. Reference Types . . . . . . . . . . . . . . . . . . . . . . . 5 59 3. Link Relation Types . . . . . . . . . . . . . . . . . . . . . 5 60 4. Redefined Relation Type Value . . . . . . . . . . . . . . . . 5 61 5. New Property Parameters . . . . . . . . . . . . . . . . . . . 8 62 5.1. Rel . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 63 5.2. Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 64 6. New Value Data Types . . . . . . . . . . . . . . . . . . . . 9 65 7. New Properties . . . . . . . . . . . . . . . . . . . . . . . 10 66 7.1. Concept . . . . . . . . . . . . . . . . . . . . . . . . . 10 67 7.2. Link . . . . . . . . . . . . . . . . . . . . . . . . . . 11 68 7.3. Refid . . . . . . . . . . . . . . . . . . . . . . . . . . 13 69 8. Redefined RELATED-TO Property . . . . . . . . . . . . . . . . 13 70 8.1. RELATED-TO . . . . . . . . . . . . . . . . . . . . . . . 14 71 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 72 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 73 10.1. iCalendar Property Registrations . . . . . . . . . . . . 16 74 10.2. iCalendar Property Parameter Registrations . . . . . . . 16 75 10.3. iCalendar Value Data Type Registrations . . . . . . . . 16 76 10.4. iCalendar RELTYPE Value Registrations . . . . . . . . . 17 77 10.5. New Reference Type Registration . . . . . . . . . . . . 17 78 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 79 12. Normative References . . . . . . . . . . . . . . . . . . . . 18 80 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19 82 1. Introduction 84 iCalendar entities often need to be related to each other or to 85 associated meta-data. These relationships can take the following 86 forms 88 Structured iCalendar: iCalendar entities are related to each other 89 in some structured way, for example as parent, sibling, before, 90 after. 92 Grouped iCalendar: iCalendar entities are related to each other as a 93 group. CATEGORIES are often used for this purpose but are 94 problematic for application developers. 96 Linked: Entities are linked to each other through typed references. 98 1.1. Structured iCalendar relationships 100 The currently existing iCalendar [RFC5545] RELATED-TO property has no 101 support for temporal relationships as used by standard project 102 management tools. 104 The RELTYPE parameter is extended to take new values defining 105 temporal relationships, a GAP parameter is defined to provide lead 106 and lag values and RELATED-TO is extended to allow URI values. These 107 changes allow the RELATED-TO property to define a richer set of 108 relationships useful for project management. 110 1.2. Grouped iCalendar relationships 112 This specification defines a new REFID property which allows 113 arbitrary groups of entities to be associated with the same key 114 value. 116 REFID is used to identify a key allowing the association of tasks 117 that are related to the same object and retrieval of a task based on 118 this key. This may be, for example, to identify the tasks associated 119 with a given project without having to communicate the task structure 120 of the project, or, for example, in a package delivery system all 121 tasks associated to a specific package. 123 As such, the presence of a REFID property imparts no meaning to the 124 event. It is merely a key to allow retrieval. This is distinct from 125 categorisation which, while allowing grouping also adds meaning to 126 the entity to which it is attached. 128 1.3. Concept relationships 130 The name CONCEPT is used by the Simple Knowledge Organization System 131 defined in [W3C.CR-skos-reference-20090317]. This more accurately 132 defines what we mean by a catgeory. It's not the words but the 133 meaning. 135 The introduction of CONCEPT allows a more structured approach to 136 categorization, with the possibility of namespaced and path-like 137 values. Unlike REFID the CONCEPT property imparts some meaning. It 138 is assumed that the value of this property will reference a well 139 defined category. 141 The current [RFC5545] CATEGORY property is used as a free form 142 'tagging' field. As such it is difficult to establish formal 143 relationships between components based on their category. 145 Rather than attempt to add semantics to the current property it 146 seeems best to continue its usage as an informal tag and establish a 147 new property with more constraints. 149 1.4. Linked relationships 151 The currently existing iCalendar standard [RFC5545] lacks a general 152 purpose method for referencing additional, external information 153 relating to calendar components. 155 This document proposes a method for referencing typed external 156 information that can provide additional information about an 157 iCalendar component. This new LINK property is closely aligned to 158 the LINK header defined in [RFC5988] 160 The LINK property defines a typed reference or relation to external 161 meta-data or related resources. By providing type and format 162 information as parameters, clients and servers are able to discover 163 interesting references and make use of them, perhaps for indexing or 164 the presentation of interesting links for the user. 166 It is often necessary to relate calendar components. The current 167 RELATED-TO property only allows for a UID which is inadequate for 168 many purposes. Allowing other types may help but might raise a 169 number of backward compatibility issues. The link property can link 170 components in different collections or even on different servers. 172 When publishing events it is useful to be able to refer back to the 173 source of that information. The actual event may have been consumed 174 from a feed or an ics file on a web site. A LINK property can 175 provide a reference to the originator of the event. 177 Beyond the need to relate elements temporally, project management 178 tools often need to be able to specify the relationships between the 179 various events and tasks which make up a project. The LINK property 180 provides such a mechanism. 182 The LINK property SHOULD NOT be treated as just another attachment. 183 The ATTACH property is being extended to handle server-side 184 management and stripping of inline data. Clients may choose to 185 handle attachments differently as they are often an integral part of 186 the message - for example, the agenda. See 187 [I-D.daboo-caldav-attachments] 189 1.5. Caching and offline use 191 To facilitate offline display the link type may identify important 192 pieces of data which should be downloaded in advance. 194 In general, the calendar entity should be self explanatory without 195 the need to download referenced meta-data such as a web page. 197 1.6. Conventions Used in This Document 199 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 200 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 201 "OPTIONAL" in this document are to be interpreted as described in 202 [RFC2119]. 204 2. Reference Types 206 The actual reference value can take three forms specified by the type 207 parameter 209 URI: The default type. This is a URI referring to the target. 211 UID: This allows for linking within a single collection and the 212 value is assumed to be another component within that collection. 214 REFERENCE: An xpointer. In an XML environment it may be necessary 215 to refer to an external XML artifact. The XPointer is defined in 216 [W3C.WD-xptr-xpointer-20021219] and allows addressing portions of 217 XML documents. 219 3. Link Relation Types 221 [RFC5988] defines two form of relation types, registered and 222 extension. Registered relation types are added to a registry defined 223 by [RFC5988] while extension relation types are specified as unique 224 unregistered URIs, (at least unregistered in the [RFC5988] registry). 226 The relation types defined here will be registered with IANA in 227 accordance with the specifications in [RFC5988]. 229 4. Redefined Relation Type Value 231 Relationship parameter type values are defined in section 3.2.15. of 232 [RFC5545]. This specification redefines that type to include the new 233 temporal relationship values FINISHTOSTART, FINISHTOFINISH, 234 STARTTOFINISH and STARTTOSTART. It also adds the DEPENDS-ON value to 235 provide a link to a component upon which the current component 236 depends. 238 Format Definition: 240 This property parameter is defined by the following notation: 242 reltypeparam = "RELTYPE" "=" 243 ("PARENT" ; Parent relationship - Default 244 / "CHILD" ; Child relationship 245 / "SIBLING" ; Sibling relationship 246 / "DEPENDS-ON" ; refers to previous task 247 / "REFID" ; Relationship based on REFID 248 / "CONCEPT" 249 ; Relationship based on CONCEPT 250 / "FINISHTOSTART" ; Temporal relationship 251 / "FINISHTOFINISH" ; Temporal relationship 252 / "STARTTOFINISH" ; Temporal relationship 253 / "STARTTOSTART" ; Temporal relationship 254 / iana-token ; Some other IANA-registered 255 ; iCalendar relationship type 256 / x-name) ; A non-standard, experimental 257 ; relationship type 259 Description: This parameter can be specified on a property that 260 references another related calendar component. The parameter may 261 specify the hierarchical relationship type of the calendar 262 component referenced by the property when the value is PARENT, 263 CHILD or SIBLING. If this parameter is not specified on an 264 allowable property, the default relationship type is PARENT. 265 Applications MUST treat x-name and iana-token values they don't 266 recognize the same way as they would the PARENT value. 268 This parameter defines the temporal relationship when the value is 269 one of the project management standard relationships 270 FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART. 271 This property will be present in the predecessor entity and will 272 refer to the successor entity. The GAP parameter specifies the 273 lead or lag time between the predecessor and the successor. In 274 the description of each temporal relationship below we refer to 275 Task-A which contains and controls the relationship and Task-B the 276 target of the relationship. 278 RELTYPE=PARENT: See [RFC5545] section 3.2.15. 280 RELTYPE=CHILD: See [RFC5545] section 3.2.15. 282 RELTYPE=SIBLING: See [RFC5545] section 3.2.15. 284 RELTYPE=DEPENDS-ON: Indicates that the current calendar component 285 depends on the referenced calendar component in some manner. For 286 example a task may be blocked waiting on the other, referenced, 287 task. 289 RELTYPE=REFID: Establishes a reference from the current component to 290 components with a REFID property which matches the value given in 291 the associated RELATED-TO property. 293 RELTYPE=CONCEPT: Establishes a reference from the current component 294 to components with a CONCEPT property which matches the value 295 given in the associated RELATED-TO property. 297 RELTYPE=FINISHTOSTART: Task-B cannot start until Task-A finishes. 298 For example, when sanding is complete, painting can begin. 300 ============ 301 | Task-A |--+ 302 ============ | 303 | 304 V 305 ============ 306 | Task-B | 307 ============ 309 Figure 1: Finish to start relationship 311 RELTYPE=FINISHTOFINISH: Task-B cannot finish before Task-A is 312 finished, that is the end of Task-A defines the end of Task-B. 313 For example, we start the potatoes, then the meat then the peas 314 but they should all be cooked at the same time. 316 ============ 317 | Task-A |--+ 318 ============ | 319 | 320 ============ | 321 | Task-B |<-+ 322 ============ 324 Figure 2: Finish to finish relationship 326 RELTYPE=STARTTOFINISH: The start of Task-A (which occurs after Task- 327 B) controls the finish of Task-B. For example, ticket sales 328 (Task-B) end when the game starts (Task-A). 330 ============ 331 +--| Task-A | 332 | ============ 333 | 334 ============ | 335 | Task-B |<-+ 336 ============ 338 Figure 3: Start to finish relationship 340 RELTYPE=STARTTOSTART: The start of Task-A triggers the start of 341 Task-B, that is Task-B can start anytime after Task-A starts. 343 ============ 344 +--| Task-A | 345 | ============ 346 | 347 | ============ 348 +->| Task-B | 349 ============ 351 Figure 4: Start to start relationship 353 5. New Property Parameters 355 5.1. Rel 357 Parameter name: REL 359 Purpose: To specify the relationship of data referenced by a LINK 360 property. 362 Format Definition: 364 This parameter is defined by the following notation: 366 relparam = "REL" "=" 367 ("SOURCE" ; Link to source of this component 368 / DQUOTE uri DQUOTE 369 / x-name ; Experimental reference type 370 / iana-token) ; Other IANA registered type 372 Description: This parameter MUST be specified on all LINK 373 properties, and defines the type of reference. This allows 374 programs consuming this data to automatically scan for references 375 they support. In addition to the values defined here any value 376 defined in [RFC5988] may be used. There is no default relation 377 type. 379 REL=SOURCE: identifies the source of the event information. 381 Registration: These relation types are registered in [RFC5988] 383 5.2. Gap 385 Parameter name: GAP 387 Purpose: To specify the length of the gap, positive or negative 388 between two temporaly related components. 390 Format Definition: 392 This parameter is defined by the following notation: 394 gapparam = "GAP" "=" dur-value 396 Description: This parameter MAY be specified on the RELATED-TO 397 property, and defines the duration of time between the predecessor 398 and successor in an interval. When positive it defines the lag 399 time between a task and its logical successor. When negative it 400 defines the lead time. 402 An example of lag time might be if task A is "paint the room" and 403 task B is "hang the drapes" then task A may be related to task B 404 with RELTYPE=FINISHTOSTART with a gap long enough for the paint to 405 dry. 407 An example of lead time might be to relate a 1 week task A to the 408 end of task B with RELTYPE=STARTTOFINISH and a negative gap of 1 409 week so they finish at the same time. 411 6. New Value Data Types 413 This specification defines the following new value types to be used 414 with the VALUE property parameter: 416 UID VALUE=UID indicates that the associated value is the UID for a 417 component. 419 REFERENCE VALUE=REFERENCE indicates that the associated value is an 420 xpointer referencing an associated XML artifact. 422 7. New Properties 424 7.1. Concept 426 Property name: CONCEPT 428 Purpose: This property defines the formal categories for a calendar 429 component. 431 Value type: URI 433 Property Parameters: IANA, and non-standard parameters can be 434 specified on this property. 436 Conformance: This property can be specified zero or more times in 437 any iCalendar component. 439 Description: This property is used to specify formal categories or 440 classifications of the calendar component. The values are useful 441 in searching for a calendar component of a particular type and 442 category. 444 Within the "VEVENT", "VTODO", or "VJOURNAL" calendar components, 445 more than one formal category can be specified by using multiple 446 CONCEPT properties. 448 This categorization is distinct from the more informal "tagging" 449 of components provided by the existing CATEGORIES property. It is 450 expected that the value of the CONCEPT property will reference an 451 external resource which provides information about the 452 categorization. 454 In addition, a structured URI value allows for hierarchical 455 categorization of events. 457 Possible category resources are the various proprietary systems, 458 for example Library of Congress, or an open source derived from 459 something like the dmoz.org data. 461 Format Definition: 463 This property is defined by the following notation: 465 concept = "CONCEPT" conceptparam ":" 466 uri CRLF 468 conceptparam = *( 469 ; 470 ; The following is OPTIONAL, 471 ; and MAY occur more than once. 472 ; 473 (";" other-param) 474 ; 475 ) 477 Example: 479 The following is an example of this property. It points to a server 480 acting as the source for the calendar object. 482 SCONCEPT:http://example.com/event-types/sports 483 CONCEPT:http://example.com/event-types/arts/music 484 CONCEPT:http://example.com/task-types/delivery 486 7.2. Link 488 Property name: LINK 490 Purpose: This property provides a reference to external information 491 about a component. 493 Value type: URI, TEXT or REFERENCE 495 Property Parameters: Non-standard, reference type or format type 496 parameters can be specified on this property. 498 Conformance: This property MAY be specified in any iCalendar 499 component. 501 Description: When used in a component the value of this property 502 points to additional information related to the component. For 503 example, it may reference the originating web server. 505 Format Definition: 507 This property is defined by the following notation: 509 link = "LINK" linkparam / 510 ( 511 ";" "VALUE" "=" "TEXT" 512 ":" text 513 ) 514 ( 515 ";" "VALUE" "=" "REFERENCE" 516 ":" text 517 ) 518 ( 519 ";" "VALUE" "=" "URI" 520 ":" uri 521 ) 522 CRLF 524 linkparam = *( 526 ; the following is MANDATORY 527 ; and MAY occur more than once 529 (";" relparam) / 531 ; the following are MANDATORY 532 ; but MUST NOT occur more than once 534 (";" fmttypeparam) / 535 (";" labelparam) / 536 ; labelparam is defined in ... 538 ; the following is OPTIONAL 539 ; and MAY occur more than once 541 (";" xparam) 543 ) 545 Example: 547 The following is an example of this property. It points to a server 548 acting as the source for the calendar object. 550 LINK;REL=SOURCE;LABEL=The Egg:http://example.com/events 552 7.3. Refid 554 Property name: REFID 556 Purpose: This property value acts as a key for associated iCalendar 557 entities. 559 Value type: TEXT 561 Property Parameters: Non-standard parameters can be specified on 562 this property. 564 Conformance: This property MAY be specified multiple times in any 565 iCalendar component. 567 Description: The value of this property is a text identifier that 568 allows associated components to be located or retrieved as a 569 whole. For example all of the events in a travel itinerary would 570 have the same REFID value. 572 Format Definition: 574 This property is defined by the following notation: 576 refid = "REFID" refidparam ":" text CRLF 578 refidparam = *( 580 ; the following is OPTIONAL 581 ; and MAY occur more than once 583 (";" xparam) 585 ) 587 Example: 589 The following is an example of this property. 591 REFID:itinerary-2014-11-17 593 8. Redefined RELATED-TO Property 594 8.1. RELATED-TO 596 Property name: RELATED-TO 598 Purpose: This property is used to represent a relationship or 599 reference between one calendar component and another. The 600 definition here extends the definition in Section 3.8.4.5. of 601 [RFC5545] by allowing URI or UID values and a GAP parameter. 603 Value type: URI, UID or TEXT 605 Property Parameters: Relationship type, IANA and non-standard 606 property parameters can be specified on this property. 608 Conformance: This property MAY be specified in any iCalendar 609 component. 611 Description: By default or when VALUE=UID is specified, the property 612 value consists of the persistent, globally unique identifier of 613 another calendar component. This value would be represented in a 614 calendar component by the "UID" property. 616 By default, the property value points to another calendar 617 component that has a PARENT relationship to the referencing 618 object. The "RELTYPE" property parameter is used to either 619 explicitly state the default PARENT relationship type to the 620 referenced calendar component or to override the default PARENT 621 relationship type and specify either a CHILD or SIBLING 622 relationship or a temporal relationship. 624 The PARENT relationship indicates that the calendar component is a 625 subordinate of the referenced calendar component. The CHILD 626 relationship indicates that the calendar component is a superior 627 of the referenced calendar component. The SIBLING relationship 628 indicates that the calendar component is a peer of the referenced 629 calendar component. 631 The FINISHTOSTART, FINISHTOFINISH, STARTTOFINISH or STARTTOSTART 632 relationships define temporal relationships as specified in the 633 reltype parameter definition. 635 Changes to a calendar component referenced by this property can 636 have an implicit impact on the related calendar component. For 637 example, if a group event changes its start or end date or time, 638 then the related, dependent events will need to have their start 639 and end dates changed in a corresponding way. Similarly, if a 640 PARENT calendar component is cancelled or deleted, then there is 641 an implied impact to the related CHILD calendar components. This 642 property is intended only to provide information on the 643 relationship of calendar components. It is up to the target 644 calendar system to maintain any property implications of this 645 relationship. 647 Format Definition: 649 This property is defined by the following notation: 651 related = "RELATED-TO" relparam ( ":" text ) / 652 ( 653 ";" "VALUE" "=" "UID" 654 ":" uid 655 ) 656 ( 657 ";" "VALUE" "=" "URI" 658 ":" uri 659 ) 660 CRLF 662 relparam = *( 663 ; 664 ; The following are OPTIONAL, 665 ; but MUST NOT occur more than once. 666 ; 667 (";" reltypeparam) / 668 (";" gapparam) / 669 ; 670 ; The following is OPTIONAL, 671 ; and MAY occur more than once. 672 ; 673 (";" other-param) 674 ; 675 ) 677 Example: 679 The following are examples of this property. 681 RELATED-TO:jsmith.part7.19960817T083000.xyzMail@example.com 683 RELATED-TO:19960401-080045-4000F192713-0052@example.com 685 RELATED-TO;VALUE=URI;RELTYPE=STARTTOFINISH: 686 http://example.com/caldav/user/jb/cal/ 687 19960401-080045-4000F192713.ics 689 9. Security Considerations 691 Applications using the LINK property need to be aware of the risks 692 entailed in using the URIs provided as values. See [RFC3986] for a 693 discussion of the security considerations relating to URIs. 695 The CONCEPT and redefined RELATED-TO property have the same issues in 696 that values may be URIs. 698 10. IANA Considerations 700 10.1. iCalendar Property Registrations 702 The following iCalendar property names have been added to the 703 iCalendar Properties Registry defined in Section 8.3.2 of [RFC5545] 705 +----------+---------+-------------+ 706 | Property | Status | Reference | 707 +----------+---------+-------------+ 708 | CONCEPT | Current | Section 7.1 | 709 | LINK | Current | Section 7.2 | 710 | REFID | Current | Section 7.3 | 711 +----------+---------+-------------+ 713 10.2. iCalendar Property Parameter Registrations 715 The following iCalendar property parameter names have been added to 716 the iCalendar Parameters Registry defined in Section 8.3.3 of 717 [RFC5545] 719 +-----------+---------+-------------+ 720 | Parameter | Status | Reference | 721 +-----------+---------+-------------+ 722 | REL | Current | Section 5.1 | 723 | GAP | Current | Section 5.2 | 724 +-----------+---------+-------------+ 726 10.3. iCalendar Value Data Type Registrations 728 The following iCalendar property parameter names have been added to 729 the iCalendar Value Data Types Registry defined in Section 8.3.4 of 730 [RFC5545] 731 +-----------------+---------+-----------+ 732 | Value Data Type | Status | Reference | 733 +-----------------+---------+-----------+ 734 | UID | Current | Section 6 | 735 | REFERENCE | Current | Section 6 | 736 +-----------------+---------+-----------+ 738 10.4. iCalendar RELTYPE Value Registrations 740 The following iCalendar "RELTYPE" values have been added to the 741 iCalendar Relationship Types Registry defined in Section 8.3.8 of 742 [RFC5545] 744 +-------------------+---------+-----------+ 745 | Relationship Type | Status | Reference | 746 +-------------------+---------+-----------+ 747 | DEPENDS-ON | Current | Section 4 | 748 | REFID | Current | Section 4 | 749 | CONCEPT | Current | Section 4 | 750 | FINISHTOSTART | Current | Section 4 | 751 | FINISHTOFINISH | Current | Section 4 | 752 | STARTTOFINISH | Current | Section 4 | 753 | STARTTOSTART | Current | Section 4 | 754 +-------------------+---------+-----------+ 756 10.5. New Reference Type Registration 758 The following link relation values have been added to the Reference 759 Types Registry defined in Section 6.2.2 of [RFC5988] 761 +--------+---------+-------------+ 762 | Name | Status | Reference | 763 +--------+---------+-------------+ 764 | SOURCE | Current | Section 5.1 | 765 +--------+---------+-------------+ 767 11. Acknowledgements 769 The author would like to thank the members of the Calendaring and 770 Scheduling Consortium technical committees and the following 771 individuals for contributing their ideas, support and comments: 773 Adrian Apthorp, Cyrus Daboo, Marten Gajda, Ken Murchison 775 The author would also like to thank the Calendaring and Scheduling 776 Consortium for advice with this specification. 778 12. Normative References 780 [I-D.daboo-caldav-attachments] 781 Daboo, C. and A. Quillaud, "CalDAV Managed Attachments", 782 draft-daboo-caldav-attachments-03 (work in progress), 783 February 2014. 785 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 786 Requirement Levels", BCP 14, RFC 2119, 787 DOI 10.17487/RFC2119, March 1997, 788 . 790 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 791 Resource Identifier (URI): Generic Syntax", STD 66, 792 RFC 3986, DOI 10.17487/RFC3986, January 2005, 793 . 795 [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and 796 Scheduling Core Object Specification (iCalendar)", 797 RFC 5545, DOI 10.17487/RFC5545, September 2009, 798 . 800 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, 801 DOI 10.17487/RFC5988, October 2010, 802 . 804 [W3C.CR-skos-reference-20090317] 805 Bechhofer, S. and A. Miles, "SKOS Simple Knowledge 806 Organization System Reference", World Wide Web Consortium 807 CR CR-skos-reference-20090317, March 2009, 808 . 810 [W3C.REC-xml-20060816] 811 Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and 812 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth 813 Edition)", World Wide Web Consortium Recommendation REC- 814 xml-20060816, August 2006, 815 . 817 [W3C.WD-xptr-xpointer-20021219] 818 DeRose, S., Daniel, R., and E. Maler, "XPointer xpointer() 819 Scheme", World Wide Web Consortium WD WD-xptr-xpointer- 820 20021219, December 2002, 821 . 823 Author's Address 825 Michael Douglass 826 Spherical Cow Group 827 226 3rd Street 828 Troy, NY 12180 829 USA 831 Email: mdouglass@sphericalcowgroup.com 832 URI: http://sphericalcowgroup.com