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Daboo 3 Internet-Draft Apple 4 Updates: 5545 (if approved) K. Murchison, Ed. 5 Intended status: Standards Track Fastmail 6 Expires: January 14, 2021 July 13, 2020 8 VALARM Extensions for iCalendar 9 draft-ietf-calext-valarm-extensions-02 11 Abstract 13 This document defines a set of extensions to the iCalendar VALARM 14 component to enhance use of alarms and improve interoperability 15 between clients and servers. 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 January 14, 2021. 34 Copyright Notice 36 Copyright (c) 2020 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 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 53 3. Extensible syntax for VALARM . . . . . . . . . . . . . . . . 3 54 4. Alarm Unique Identifier . . . . . . . . . . . . . . . . . . . 5 55 5. Alarm Related To . . . . . . . . . . . . . . . . . . . . . . 6 56 6. Alarm Acknowledgement . . . . . . . . . . . . . . . . . . . . 6 57 6.1. Acknowledged Property . . . . . . . . . . . . . . . . . . 7 58 7. Snoozing Alarms . . . . . . . . . . . . . . . . . . . . . . . 8 59 7.1. Relationship Type Property Parameter . . . . . . . . . . 9 60 8. Alarm Proximity Trigger . . . . . . . . . . . . . . . . . . . 9 61 8.1. Proximity Property . . . . . . . . . . . . . . . . . . . 10 62 8.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . 11 63 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 64 10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 11 65 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 66 11.1. Property Registrations . . . . . . . . . . . . . . . . . 12 67 11.2. Relationship Types Registry . . . . . . . . . . . . . . 12 68 11.3. Proximity Value Registry . . . . . . . . . . . . . . . . 12 69 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 70 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 71 13.1. Normative References . . . . . . . . . . . . . . . . . . 13 72 13.2. Informative References . . . . . . . . . . . . . . . . . 13 73 13.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 14 74 Appendix A. Change History (To be removed by RFC Editor before 75 publication) . . . . . . . . . . . . . . . . . . . . 14 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 78 1. Introduction 80 The iCalendar [RFC5545] specification defines a set of components 81 used to describe calendar data. One of those is the "VALARM" 82 component which appears as a sub-component of "VEVENT" and "VTODO" 83 components. The "VALARM" component is used to specify a reminder for 84 an event or task. Different alarm actions are possible, as are 85 different ways to specify how the alarm is triggered. 87 As iCalendar has become more widely used and as client-server 88 protocols such as CalDAV [RFC4791] have become more prevalent, 89 several issues with "VALARM" components have arisen. Most of these 90 relate to the need to extend the existing "VALARM" component with new 91 properties and behaviors to allow clients and servers to accomplish 92 specific tasks in an interoperable manner. For example, clients 93 typically need a way to specify that an alarm has been dismissed by a 94 calendar user, or has been "snoozed" by a set amount of time. To 95 date, this has been done through the use of custom "X-" properties 96 specific to each client implementation, leading to poor 97 interoperability. 99 This specification defines a set of extensions to "VALARM" components 100 to cover common requirements for alarms not currently addressed in 101 iCalendar. Each extension is defined in a separate section below. 102 For the most part, each extension can be supported independently of 103 the others, though in some cases one extension will require another. 104 In addition, this specification describes mechanisms by which clients 105 can interoperably implement common features such as "snoozing". 107 2. Conventions Used in This Document 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 111 "OPTIONAL" in this document are to be interpreted as described in BCP 112 14 [1] [RFC2119] [RFC8174] when, and only when, they appear in all 113 capitals, as shown here. 115 When XML element types in the namespaces "DAV:" and 116 "urn:ietf:params:xml:ns:caldav" are referenced in this document 117 outside of the context of an XML fragment, the string "DAV:" and 118 "CALDAV:" will be prefixed to the element type names respectively. 120 3. Extensible syntax for VALARM 122 Section 3.6.6 of [RFC5545] defines the syntax for "VALARM" components 123 and properties within them. However, as written, it is hard to 124 extend this by adding, e.g., a new property common to all types of 125 alarm. Since many of the extensions defined in this document need to 126 extend the base syntax, an alternative form for the base syntax is 127 defined here, with the goal of simplifying specification of the 128 extensions. 130 A "VALARM" calendar component is re-defined by the following 131 notation: 133 alarmcext = "BEGIN" ":" "VALARM" CRLF 134 alarmprop 135 "END" ":" "VALARM" CRLF 137 alarmprop = *( 139 ; the following are REQUIRED, 140 ; but MUST NOT occur more than once 142 action / trigger / 143 ; one set of action properties MUST be 144 ; present and MUST match the action specified 145 ; in the ACTION property 147 actionprops / 149 ; the following is OPTIONAL, 150 ; and MAY occur more than once 152 x-prop / iana-prop 154 ) 156 actionprops = audiopropext / disppropext / emailpropext 158 audiopropext = *( 160 ; 'duration' and 'repeat' are both OPTIONAL, 161 ; and MUST NOT occur more than once each, 162 ; but if one occurs, so MUST the other 164 duration / repeat / 166 ; the following is OPTIONAL, 167 ; but MUST NOT occur more than once 169 attach 171 ) 173 disppropext = *( 175 ; the following are REQUIRED, 176 ; but MUST NOT occur more than once 178 description / 180 ; 'duration' and 'repeat' are both OPTIONAL, 181 ; and MUST NOT occur more than once each, 182 ; but if one occurs, so MUST the other 184 duration / repeat 186 ) 188 emailpropext = *( 190 ; the following are all REQUIRED, 191 ; but MUST NOT occur more than once 193 description / summary / 195 ; the following is REQUIRED, 196 ; and MAY occur more than once 198 attendee / 200 ; 'duration' and 'repeat' are both OPTIONAL, 201 ; and MUST NOT occur more than once each, 202 ; but if one occurs, so MUST the other 204 duration / repeat 206 ; the following is OPTIONAL, 207 ; and MAY occur more than once 209 attach 211 ) 213 4. Alarm Unique Identifier 215 This extension adds a "UID" property to "VALARM" components to allow 216 a unique identifier to be specified. The value of this property can 217 then be used to refer uniquely to the "VALARM" component. 219 The "UID" property defined here follows the definition in 220 Section 3.8.4.7 of [RFC5545] with the security and privacy updates in 221 Section 5.3 of [RFC7986]. In particular it MUST be a globally unique 222 identifier that does not contain any security- or privacy-sensitive 223 information. 225 The "VALARM" component defined in Section 3 is extended here as: 227 alarmprop /= *( 229 ; the following is OPTIONAL, 230 ; but MUST NOT occur more than once 232 uid 234 ) 236 5. Alarm Related To 238 It is often convenient to relate one or more "VALARM" components to 239 other "VALARM" components (e.g., see Section 7). This can be 240 accomplished if the "VALARM" components each have their own "UID" 241 property (as per Section 4). 243 This specification updates the usage of the "RELATED-TO" property 244 defined in Section 3.8.4.5 of [RFC5545] to enable its use with 245 "VALARM" components. Specific types of relationships between 246 "VALARM" components can be identified by registering new values for 247 the "RELTYPE" property parameter defined in Section 3.2.15 of 248 [RFC5545]. 250 The "VALARM" component defined in Section 3 is extended here as: 252 alarmprop /= *( 254 ; the following is OPTIONAL, 255 ; but MAY occur more than once 257 related 259 ) 261 6. Alarm Acknowledgement 263 There is currently no way for a "VALARM" component to indicate 264 whether it has been triggered and acknowledged. With the advent of a 265 standard client/server protocol for calendaring and scheduling data 266 ([RFC4791]) it is quite possible for an event with an alarm to exist 267 on multiple clients in addition to the server. If each of those is 268 responsible for performing the action when an alarm triggers, then 269 multiple "alerts" are generated by different devices. In such a 270 situation, a calendar user would like to be able to "dismiss" the 271 alarm on one device and have it automatically dismissed on the others 272 too. 274 Also, with recurring events that have alarms, it is important to know 275 when the last alarm in the recurring set was acknowledged, so that 276 the client can determine whether past alarms have been missed. 278 To address these needs, this specification adds an "ACKNOWLEDGED" 279 property to "VALARM" components to indicate when the alarm was last 280 sent or acknowledged. This is defined by the syntax below. 282 alarmprop /= *( 284 ; the following is OPTIONAL, 285 ; but MUST NOT occur more than once 287 acknowledged 289 ) 291 6.1. Acknowledged Property 293 Property Name: ACKNOWLEDGED 295 Purpose: This property specifies the UTC date and time at which the 296 corresponding alarm was last sent or acknowledged. 298 Value Type: DATE-TIME 300 Property Parameters: IANA and non-standard property parameters can 301 be specified on this property. 303 Conformance: This property can be specified within "VALARM" calendar 304 components. 306 Description: This property is used to specify when an alarm was last 307 sent or acknowledged. This allows clients to determine when a 308 pending alarm has been acknowledged by a calendar user so that any 309 alerts can be dismissed across multiple devices. It also allows 310 clients to track repeating alarms or alarms on recurring events or 311 to-dos to ensure that the right number of missed alarms can be 312 tracked. 314 Clients SHOULD set this property to the current date-time value in 315 UTC when a calendar user acknowledges a pending alarm. Certain 316 kinds of alarm may not provide feedback as to when the calendar 317 user sees them, for example email based alerts. For those kinds 318 of alarms, the client SHOULD set this property when the alarm is 319 triggered and the action successfully carried out. 321 When an alarm is triggered on a client, clients can check to see 322 if an "ACKNOWLEDGED" property is present. If it is, and the value 323 of that property is greater than or equal to the computed trigger 324 time for the alarm, then the client SHOULD NOT trigger the alarm. 325 Similarly, if an alarm has been triggered and an "alert" presented 326 to a calendar user, clients can monitor the iCalendar data to 327 determine whether an "ACKNOWLEDGED" property is added or changed 328 in the alarm component. If the value of any "ACKNOWLEDGED" 329 property in the alarm changes and is greater than or equal to the 330 trigger time of the alarm, then clients SHOULD dismiss or cancel 331 any "alert" presented to the calendar user. 333 Format Definition: This property is defined by the following 334 notation: 336 acknowledged = "ACKNOWLEDGED" acknowledgedparam ":" datetime CRLF 338 acknowledgedparam = *( 340 ; the following is OPTIONAL, 341 ; and MAY occur more than once 343 (";" other-param) 345 ) 347 Example: The following is an example of this property: 349 ACKNOWLEDGED:20090604T084500Z 351 7. Snoozing Alarms 353 Users often want to "snooze" an alarm, and this specification defines 354 a standard approach to accomplish that. 356 To "snooze" an alarm, clients create a new "VALARM" component within 357 the parent component of the "VALARM" that was triggered and is being 358 "snoozed" (i.e., as a "sibling" component of the "VALARM" being 359 snoozed). The new "VALARM" MUST be set to trigger at the user's 360 chosen "snooze" interval after the original alarm triggered. Clients 361 SHOULD use an absolute "TRIGGER" property with a "DATE-TIME" value 362 specified in UTC. 364 Clients SHOULD add a "RELATED-TO" property to the new "VALARM" 365 component with a value set to the "UID" property value of the 366 "VALARM" component being snoozed. If the "VALARM" component being 367 snoozed does not already have a "UID" property, the client SHOULD add 368 one. The "RELATED-TO" property added to the new "VALARM" component 369 SHOULD include a "RELTYPE" property parameter with a value set to 370 "SNOOZE". 372 When the "snooze" alarm is triggered and dismissed the client SHOULD 373 remove the corresponding "VALARM" component, or set the 374 "ACKNOWLEDGED" property (see Section 6.1). Alternatively, if the 375 "snooze" alarm is itself "snoozed", the client SHOULD remove the 376 original "snooze" alarm and create a new one, with the appropriate 377 trigger time and relationship set. 379 7.1. Relationship Type Property Parameter 381 This specification adds the "SNOOZE" relationship type for use with 382 the "RELTYPE" property defined in Section 3.2.15 of [RFC5545]. This 383 is used to relate a "snoozed" "VALARM" component to the original 384 alarm that the "snooze" was generated for. 386 8. Alarm Proximity Trigger 388 VALARMs are currently triggered when a specific date-time is reached. 389 It is also desirable to be able to trigger alarms based on location, 390 e.g. when arriving at or departing from a particular location. 392 This specification adds the following properties to "VALARM" 393 components to indicate when an alarm can be triggered based on 394 location. 396 "PROXIMITY" - indicates that a location based trigger is to be 397 used and which direction of motion is used for the trigger 399 "STRUCTURED-LOCATION" [I-D.ietf-calext-eventpub-extensions] - used 400 to indicate the actual location to trigger off, specified using a 401 geo: URI [RFC5870] which allows for two or three coordinate values 402 with an optional uncertainty 404 alarmprop /= *( 406 ; the following is OPTIONAL, 407 ; but MUST NOT occur more than once 409 proximity / 411 ; the following is OPTIONAL, 412 ; and MAY occur more than once, but only 413 ; when a PROXIMITY property is also present 415 structured-location 417 ) 419 Typically, when a "PROXIMITY" property is used there is no need to 420 specify a time-based trigger using the "TRIGGER" property. However, 421 since "TRIGGER" is defined as a required property for a "VALARM" 422 component, for backwards compatibility it has to be present, but 423 ignored. To indicate a "TRIGGER" that is to be ignored, clients 424 SHOULD use a value a long time in the past. A value of 425 "19760401T005545Z" has been commonly used for this purpose. 427 8.1. Proximity Property 429 Property Name: PROXIMITY 431 Purpose: This property indicates that a location based trigger is 432 applied to an alarm. 434 Value Type: TEXT 436 Property Parameters: IANA and non-standard property parameters can 437 be specified on this property. 439 Conformance: This property can be specified within "VALARM" calendar 440 components. 442 Description: This property is used to indicate that an alarm has a 443 location-based trigger. Its value identifies the direction of 444 motion used to trigger the alarm. One or more location values are 445 set using "STRUCTURED-LOCATION" properties. 447 When the property value is set to "ARRIVE", the alarm is triggered 448 when the calendar user agent arrives in the vicinity of any of the 449 specified locations. When set to "DEPART", the alarm is triggered 450 when the calendar user agent departs from the vicinity of any 451 specified locations. 453 When the property value is set to "CONNECT", the alarm is 454 triggered when the calendar user agent connects to a Bluetooth(R) 455 [BTcore]-enabled automobile. When set to "DISCONNECT", the alarm 456 is triggered when the calendar user agent disconnects from a 457 Bluetooth(R)-enabled automobile. 459 Format Definition: This property is defined by the following 460 notation: 462 proximity = "PROXIMITY" proximityparam ":" proximityvalue CRLF 464 proximityparam = *( 466 ; the following is OPTIONAL, 467 ; and MAY occur more than once 469 (";" other-param) 471 ) 473 proximityvalue = "ARRIVE" / "DEPART" / 474 "CONNECT" / "DISCONNECT" / iana-token / x-name 476 Example: The following is an example of this property: 478 PROXIMITY:ARRIVE 480 8.2. Example 482 The following example shows a "VALARM" component with a proximity 483 trigger set to trigger when the device running the calendar user 484 agent leaves the vicinity defined by the structured location 485 property. Note use of the "u=" parameter with the "geo" URI to 486 define the precision of the location determination. 488 BEGIN:VALARM 489 UID:77D80D14-906B-4257-963F-85B1E734DBB6 490 TRIGGER;VALUE=DATE-TIME:19760401T005545Z 491 ACTION:DISPLAY 492 DESCRIPTION:Remember to buy milk 493 TRIGGER;VALUE=DATE-TIME:19760401T005545Z 494 PROXIMITY:DEPART 495 STRUCTURED-LOCATION;VALUE=URI:geo:40.443,-79.945;u=10 496 END:VALARM 498 9. Security Considerations 500 VALARMs, if not monitored properly, can be used to "spam" users and/ 501 or leak personal information. For instance, an unwanted audio or 502 display alert could be considered spam. Or an email alert could be 503 used to leak a user's location to a third party or to send 504 unsolicited email to multiple users. Therefore, CalDAV clients and 505 servers that accept iCalendar data from a third party (e.g. via iTIP 506 [RFC5546], a subscription feed, or a shared calendar) SHOULD remove 507 all VALARMs from the data prior to storing in their calendar system. 509 10. Privacy Considerations 511 Proximity VALARMs, if not used carefully, can leak a user's past, 512 present, or future location. For instance, storing an iCalendar 513 resource containing proxmity VALARMs to a shared calendar on CalDAV 514 server can expose to anyone that has access to that calendar the 515 user's intent to leave from or arrive at a particular location at 516 some future time. Furthermore, if a CalDAV client updates the shared 517 iCalendar resource with an ACKNOWLEDGED property when the alarm is 518 triggered, will leak the exact date and time that the user left from 519 or arrived at the location. Therefore, CalDAV clients that implement 520 proximity alarms SHOULD give users the option of storing and/or 521 acknowledging the alarms on the local device only and not storing the 522 alarm and/or acknowledgment on a remote server. 524 11. IANA Considerations 526 11.1. Property Registrations 528 This document defines the following new iCalendar properties to be 529 added to the registry defined in Section 8.2.3 of [RFC5545]: 531 +--------------+---------+----------------------+ 532 | Property | Status | Reference | 533 +--------------+---------+----------------------+ 534 | ACKNOWLEDGED | Current | RFCXXXX, Section 6.1 | 535 | PROXIMITY | Current | RFCXXXX, Section 8.1 | 536 +--------------+---------+----------------------+ 538 11.2. Relationship Types Registry 540 This document defines the following new iCalendar relationship type 541 to be added to the registry defined in Section 8.3.8 of [RFC5545]: 543 +-------------------+---------+----------------------+ 544 | Relationship Type | Status | Reference | 545 +-------------------+---------+----------------------+ 546 | SNOOZE | Current | RFCXXXX, Section 7.1 | 547 +-------------------+---------+----------------------+ 549 11.3. Proximity Value Registry 551 This document creates a new iCalendar registry for values of the 552 "PROXIMITY" property: 554 +------------+---------+----------------------+ 555 | Value | Status | Reference | 556 +------------+---------+----------------------+ 557 | ARRIVE | Current | RFCXXXX, Section 8.1 | 558 | DEPART | Current | RFCXXXX, Section 8.1 | 559 | CONNECT | Current | RFCXXXX, Section 8.1 | 560 | DISCONNECT | Current | RFCXXXX, Section 8.1 | 561 +------------+---------+----------------------+ 563 12. Acknowledgments 565 This specification came about via discussions at the Calendaring and 566 Scheduling Consortium. Also, thanks to the following for providing 567 feedback: Bernard Desruisseaux, Mike Douglass, Jacob Farkas, Jeffrey 568 Harris, and Ciny Joy. 570 13. References 572 13.1. Normative References 574 [I-D.ietf-calext-eventpub-extensions] 575 Douglass, M., "Event Publishing Extensions to iCalendar", 576 draft-ietf-calext-eventpub-extensions-15 (work in 577 progress), October 2019. 579 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 580 Requirement Levels", BCP 14, RFC 2119, 581 DOI 10.17487/RFC2119, March 1997, 582 . 584 [RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault, 585 "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791, 586 DOI 10.17487/RFC4791, March 2007, 587 . 589 [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and 590 Scheduling Core Object Specification (iCalendar)", 591 RFC 5545, DOI 10.17487/RFC5545, September 2009, 592 . 594 [RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource 595 Identifier for Geographic Locations ('geo' URI)", 596 RFC 5870, DOI 10.17487/RFC5870, June 2010, 597 . 599 [RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986, 600 DOI 10.17487/RFC7986, October 2016, 601 . 603 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 604 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 605 May 2017, . 607 13.2. Informative References 609 [BTcore] Bluetooth Special Interest Group, "Bluetooth Core 610 Specification Version 5.0", December 2016, 611 . 614 [RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent 615 Interoperability Protocol (iTIP)", RFC 5546, 616 DOI 10.17487/RFC5546, December 2009, 617 . 619 13.3. URIs 621 [1] https://tools.ietf.org/html/bcp14 623 Appendix A. Change History (To be removed by RFC Editor before 624 publication) 626 Changes in ietf-02: 628 1. Addressed some WGLC comments from Daniel Migault. 630 Changes in ietf-01: 632 1. Reintroduced the RELATED-TO property for VALARMs and the SNOOZE 633 value for the RELTYPE property parameter. 635 2. Add Privacy Considerations section. 637 Changes in ietf-00: 639 1. Submitted as CALEXT draft. 641 Changes in daboo-05: 643 1. Added Murchison as editor. 645 2. Updated keywords boilerplate. 647 3. Added reference to UID security/privacy recommendations. 649 4. Removed default alarms. 651 5. Removed ALARM-AGENT property. 653 6. Added text about using TRIGGER value in the past in addition to 654 ACTION:NONE to have a default alarm be ignored. 656 7. Removed text about related alarms. 658 8. Removed URL alarm action. 660 9. Added reference to draft-ietf-calext-eventpub-extensions for 661 STRUCTURED-LOCATION. 663 10. Added CONNECT and DISCONNECT PROXIMITY property values. 665 11. Added Security Considerations. 667 12. Editorial fixes. 669 Changes in daboo-04: 671 1. Changed "ID" to "AGENT-ID". 673 2. Add more text on using "ACKNOWLEDGED" property. 675 3. Add "RELATED-TO" as a valid property for VALARMs. 677 4. Add "SNOOZE" relationship type for use with VALARMs. 679 5. State that "TRIGGER" is typically ignored in proximity alarms. 681 6. Added "PROXIMITY" value registry. 683 7. Added a lot more detail on default alarms including new action 684 and property. 686 Changes in daboo-03: none - resubmission of -02 688 Changes in daboo-02: 690 1. Updated to 5545 reference. 692 2. Clarified use of absolute trigger in UTC in snooze alarms 694 3. Snooze alarms should be removed when completed 696 4. Removed status and replaced last-triggered by acknowledged 697 property 699 5. Added location-based trigger 701 6. IANA registry tables added 703 Changes in daboo-01: 705 1. Removed DESCRIPTION as an allowed property in the URI alarm. 707 2. Added statement about what to do when ALARM-AGENT is not present. 709 3. Allow multiple ALARM-AGENT properties to be present. 711 4. Removed SNOOZE-UNTIL - snoozing now accomplished by creating a 712 new VALARM. 714 5. Remove VALARM by reference section. 716 6. Added more detail to CalDAV default alarms. 718 Authors' Addresses 720 Cyrus Daboo 721 Apple Inc. 722 1 Infinite Loop 723 Cupertino, CA 95014 724 USA 726 Email: cyrus@daboo.name 727 URI: http://www.apple.com/ 729 Kenneth Murchison (editor) 730 Fastmail US LLC 731 1429 Walnut St, Suite 1201 732 Philadephia, PA 19102 733 USA 735 Email: murch@fastmailteam.com 736 URI: http://www.fastmail.com/