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Murchison, Ed. 5 Intended status: Standards Track Fastmail 6 Expires: August 19, 2021 February 15, 2021 8 VALARM Extensions for iCalendar 9 draft-ietf-calext-valarm-extensions-05 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 This document updates RFC5545. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on August 19, 2021. 36 Copyright Notice 38 Copyright (c) 2021 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 55 3. Extensible syntax for VALARM . . . . . . . . . . . . . . . . 3 56 4. Alarm Unique Identifier . . . . . . . . . . . . . . . . . . . 5 57 5. Alarm Related To . . . . . . . . . . . . . . . . . . . . . . 6 58 6. Alarm Acknowledgement . . . . . . . . . . . . . . . . . . . . 6 59 6.1. Acknowledged Property . . . . . . . . . . . . . . . . . . 7 60 7. Snoozing Alarms . . . . . . . . . . . . . . . . . . . . . . . 8 61 7.1. Relationship Type Property Parameter . . . . . . . . . . 9 62 8. Alarm Proximity Trigger . . . . . . . . . . . . . . . . . . . 9 63 8.1. Proximity Property . . . . . . . . . . . . . . . . . . . 10 64 8.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . 11 65 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 66 10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12 67 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 68 11.1. Property Registrations . . . . . . . . . . . . . . . . . 12 69 11.2. Relationship Types Registry . . . . . . . . . . . . . . 12 70 11.3. Proximity Value Registry . . . . . . . . . . . . . . . . 12 71 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 72 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 73 13.1. Normative References . . . . . . . . . . . . . . . . . . 13 74 13.2. Informative References . . . . . . . . . . . . . . . . . 14 75 Appendix A. Change History (To be removed by RFC Editor before 76 publication) . . . . . . . . . . . . . . . . . . . . 14 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 79 1. Introduction 81 The iCalendar [RFC5545] specification defines a set of components 82 used to describe calendar data. One of those is the "VALARM" 83 component which appears as a sub-component of "VEVENT" and "VTODO" 84 components. The "VALARM" component is used to specify a reminder for 85 an event or task. Different alarm actions are possible, as are 86 different ways to specify how the alarm is triggered. 88 As iCalendar has become more widely used and as client-server 89 protocols such as CalDAV [RFC4791] have become more prevalent, 90 several issues with "VALARM" components have arisen. Most of these 91 relate to the need to extend the existing "VALARM" component with new 92 properties and behaviors to allow clients and servers to accomplish 93 specific tasks in an interoperable manner. For example, clients 94 typically need a way to specify that an alarm has been dismissed by a 95 calendar user, or has been "snoozed" by a set amount of time. To 96 date, this has been done through the use of custom "X-" properties 97 specific to each client implementation, leading to poor 98 interoperability. 100 This specification defines a set of extensions to "VALARM" components 101 to cover common requirements for alarms not currently addressed in 102 iCalendar. Each extension is defined in a separate section below. 103 For the most part, each extension can be supported independently of 104 the others, though in some cases one extension will require another. 105 In addition, this specification describes mechanisms by which clients 106 can interoperably implement common features such as "snoozing". 108 2. Conventions Used in This Document 110 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 111 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 112 "OPTIONAL" in this document are to be interpreted as described in 113 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 114 capitals, as shown here. 116 When XML element types in the namespaces "DAV:" and 117 "urn:ietf:params:xml:ns:caldav" are referenced in this document 118 outside of the context of an XML fragment, the string "DAV:" and 119 "CALDAV:" will be prefixed to the element type names respectively. 121 3. Extensible syntax for VALARM 123 Section 3.6.6 of [RFC5545] defines the syntax for "VALARM" components 124 and properties within them. However, as written, it is hard to 125 extend this by adding, e.g., a new property common to all types of 126 alarm. Since many of the extensions defined in this document need to 127 extend the base syntax, an alternative form for the base syntax is 128 defined here, with the goal of simplifying specification of the 129 extensions. 131 A "VALARM" calendar component is re-defined by the following 132 notation: 134 alarmcext = "BEGIN" ":" "VALARM" CRLF 135 *alarmprop 136 "END" ":" "VALARM" CRLF 138 alarmprop = ( 140 ; the following are REQUIRED, 141 ; but MUST NOT occur more than once 143 action / trigger / 144 ; one set of action properties MUST be 145 ; present and MUST match the action specified 146 ; in the ACTION property 148 actionprops / 150 ; the following are OPTIONAL, 151 ; and MAY occur more than once 153 x-prop / iana-prop 155 ) 157 actionprops = *audiopropext / *disppropext / *emailpropext 159 audiopropext = ( 161 ; 'duration' and 'repeat' are both OPTIONAL, 162 ; and MUST NOT occur more than once each, 163 ; but if one occurs, so MUST the other 165 duration / repeat / 167 ; the following is OPTIONAL, 168 ; but MUST NOT occur more than once 170 attach 172 ) 174 disppropext = ( 176 ; the following are REQUIRED, 177 ; but MUST NOT occur more than once 179 description / 181 ; 'duration' and 'repeat' are both OPTIONAL, 182 ; and MUST NOT occur more than once each, 183 ; but if one occurs, so MUST the other 185 duration / repeat 187 ) 189 emailpropext = ( 191 ; the following are all REQUIRED, 192 ; but MUST NOT occur more than once 194 description / summary / 196 ; the following is REQUIRED, 197 ; and MAY occur more than once 199 attendee / 201 ; 'duration' and 'repeat' are both OPTIONAL, 202 ; and MUST NOT occur more than once each, 203 ; but if one occurs, so MUST the other 205 duration / repeat 207 ; the following is OPTIONAL, 208 ; and MAY occur more than once 210 attach 212 ) 214 4. Alarm Unique Identifier 216 This extension adds a "UID" property to "VALARM" components to allow 217 a unique identifier to be specified. The value of this property can 218 then be used to refer uniquely to the "VALARM" component. 220 The "UID" property defined here follows the definition in 221 Section 3.8.4.7 of [RFC5545] with the security and privacy updates in 222 Section 5.3 of [RFC7986]. In particular it MUST be a globally unique 223 identifier that does not contain any security- or privacy-sensitive 224 information. 226 The "VALARM" component defined in Section 3 is extended here as: 228 alarmprop =/ ( 230 ; the following is OPTIONAL, 231 ; but MUST NOT occur more than once 233 uid 235 ) 237 5. Alarm Related To 239 It is often convenient to relate one or more "VALARM" components to 240 other "VALARM" components (e.g., see Section 7). This can be 241 accomplished if the "VALARM" components each have their own "UID" 242 property (as per Section 4). 244 This specification updates the usage of the "RELATED-TO" property 245 defined in Section 3.8.4.5 of [RFC5545] to enable its use with 246 "VALARM" components. Specific types of relationships between 247 "VALARM" components can be identified by registering new values for 248 the "RELTYPE" property parameter defined in Section 3.2.15 of 249 [RFC5545]. 251 The "VALARM" component defined in Section 3 is extended here as: 253 alarmprop =/ ( 255 ; the following is OPTIONAL, 256 ; and MAY occur more than once 258 related 260 ) 262 6. Alarm Acknowledgement 264 There is currently no way for a "VALARM" component to indicate 265 whether it has been triggered and acknowledged. With the advent of a 266 standard client/server protocol for calendaring and scheduling data 267 ([RFC4791]) it is quite possible for an event with an alarm to exist 268 on multiple clients in addition to the server. If each of those is 269 responsible for performing the action when an alarm triggers, then 270 multiple "alerts" are generated by different devices. In such a 271 situation, a calendar user would like to be able to "dismiss" the 272 alarm on one device and have it automatically dismissed on the others 273 too. 275 Also, with recurring events that have alarms, it is important to know 276 when the last alarm in the recurring set was acknowledged, so that 277 the client can determine whether past alarms have been missed. 279 To address these needs, this specification adds an "ACKNOWLEDGED" 280 property to "VALARM" components to indicate when the alarm was last 281 sent or acknowledged. This is defined by the syntax below. 283 alarmprop =/ ( 285 ; the following is OPTIONAL, 286 ; but MUST NOT occur more than once 288 acknowledged 290 ) 292 6.1. Acknowledged Property 294 Property Name: ACKNOWLEDGED 296 Purpose: This property specifies the UTC date and time at which the 297 corresponding alarm was last sent or acknowledged. 299 Value Type: DATE-TIME 301 Property Parameters: IANA and non-standard property parameters can 302 be specified on this property. 304 Conformance: This property can be specified within "VALARM" calendar 305 components. 307 Description: This property is used to specify when an alarm was last 308 sent or acknowledged. This allows clients to determine when a 309 pending alarm has been acknowledged by a calendar user so that any 310 alerts can be dismissed across multiple devices. It also allows 311 clients to track repeating alarms or alarms on recurring events or 312 to-dos to ensure that the right number of missed alarms can be 313 tracked. 315 Clients SHOULD set this property to the current date-time value in 316 UTC when a calendar user acknowledges a pending alarm. Certain 317 kinds of alarms, such as email-based alerts, might not provide 318 feedback as to when the calendar user sees them. For those kinds 319 of alarms, the client SHOULD set this property when the alarm is 320 triggered and the action successfully carried out. 322 When an alarm is triggered on a client, clients can check to see 323 if an "ACKNOWLEDGED" property is present. If it is, and the value 324 of that property is greater than or equal to the computed trigger 325 time for the alarm, then the client SHOULD NOT trigger the alarm. 326 Similarly, if an alarm has been triggered and an "alert" presented 327 to a calendar user, clients can monitor the iCalendar data to 328 determine whether an "ACKNOWLEDGED" property is added or changed 329 in the alarm component. If the value of any "ACKNOWLEDGED" 330 property in the alarm changes and is greater than or equal to the 331 trigger time of the alarm, then clients SHOULD dismiss or cancel 332 any "alert" presented to the calendar user. 334 Format Definition: This property is defined by the following 335 notation: 337 acknowledged = "ACKNOWLEDGED" *acknowledgedparam ":" datetime CRLF 339 acknowledgedparam = ( 341 ; the following is OPTIONAL, 342 ; and MAY occur more than once 344 (";" other-param) 346 ) 348 Example: The following is an example of this property: 350 ACKNOWLEDGED:20090604T084500Z 352 7. Snoozing Alarms 354 Users often want to "snooze" an alarm, and this specification defines 355 a standard approach to accomplish that. 357 To "snooze" an alarm, clients create a new "VALARM" component within 358 the parent component of the "VALARM" that was triggered and is being 359 "snoozed" (i.e., as a "sibling" component of the "VALARM" being 360 snoozed). The new "VALARM" MUST be set to trigger at the user's 361 chosen "snooze" interval after the original alarm triggered. Clients 362 SHOULD use an absolute "TRIGGER" property with a "DATE-TIME" value 363 specified in UTC. 365 Clients MUST add a "RELATED-TO" property to the new "VALARM" 366 component with a value set to the "UID" property value of the 367 "VALARM" component being snoozed. If the "VALARM" component being 368 snoozed does not already have a "UID" property, the client MUST add 369 one. The "RELATED-TO" property added to the new "VALARM" component 370 MUST include a "RELTYPE" property parameter with a value set to 371 "SNOOZE". 373 When the "snooze" alarm is triggered and dismissed the client MUST do 374 one of the following with the corresponding "VALARM" component: 376 o Set the "ACKNOWLEDGED" property (see Section 6.1) 378 o Remove the component 379 Alternatively, if the "snooze" alarm is itself "snoozed", the client 380 MUST remove the original "snooze" alarm and create a new one, with 381 the appropriate trigger time and relationship set. 383 Note that regardless of the final disposition of the "snooze" alarm 384 when triggered, the original "VALARM" component is left unchanged. 386 7.1. Relationship Type Property Parameter 388 This specification adds the "SNOOZE" relationship type for use with 389 the "RELTYPE" property defined in Section 3.2.15 of [RFC5545]. This 390 is used when relating a "snoozed" "VALARM" component to the original 391 alarm that the "snooze" was generated for. 393 8. Alarm Proximity Trigger 395 VALARMs are currently triggered when a specific date-time is reached. 396 It is also desirable to be able to trigger alarms based on location, 397 e.g. when arriving at or departing from a particular location. 399 This specification adds the following properties to "VALARM" 400 components to indicate when an alarm can be triggered based on 401 location. 403 "PROXIMITY" - indicates that a location based trigger is to be 404 used and which direction of motion is used for the trigger 406 "STRUCTURED-LOCATION" [I-D.ietf-calext-eventpub-extensions] - used 407 to indicate the actual location to trigger off, specified using a 408 geo: URI [RFC5870] which allows for two or three coordinate values 409 with an optional uncertainty 411 alarmprop =/ ( 413 ; the following is OPTIONAL, 414 ; but MUST NOT occur more than once 416 proximity / 418 ; the following is OPTIONAL, 419 ; and MAY occur more than once, but only 420 ; when a PROXIMITY property is also present 422 structured-location 424 ) 426 Typically, when a "PROXIMITY" property is used there is no need to 427 specify a time-based trigger using the "TRIGGER" property. However, 428 since "TRIGGER" is defined as a required property for a "VALARM" 429 component, for backwards compatibility it has to be present, but 430 ignored. To indicate a "TRIGGER" that is to be ignored, clients 431 SHOULD use a value a long time in the past. A value of 432 "19760401T005545Z" has been commonly used for this purpose. 434 8.1. Proximity Property 436 Property Name: PROXIMITY 438 Purpose: This property indicates that a location based trigger is 439 applied to an alarm. 441 Value Type: TEXT 443 Property Parameters: IANA and non-standard property parameters can 444 be specified on this property. 446 Conformance: This property can be specified within "VALARM" calendar 447 components. 449 Description: This property is used to indicate that an alarm has a 450 location-based trigger. Its value identifies the direction of 451 motion used to trigger the alarm. One or more location values 452 MUST be set using "STRUCTURED-LOCATION" properties. 454 When the property value is set to "ARRIVE", the alarm is triggered 455 when the calendar user agent arrives in the vicinity of any of the 456 specified locations. When set to "DEPART", the alarm is triggered 457 when the calendar user agent departs from the vicinity of any 458 specified locations. Note that the meaning of "vicinity" in this 459 context is implementation defined. 461 When the property value is set to "CONNECT", the alarm is 462 triggered when the calendar user agent connects to an automobile 463 that is enabled for Bluetooth(R) [BTcore]. When set to 464 "DISCONNECT", the alarm is triggered when the calendar user agent 465 disconnects from an automobile that is enabled for Bluetooth(R). 467 Format Definition: This property is defined by the following 468 notation: 470 proximity = "PROXIMITY" *proximityparam ":" proximityvalue CRLF 472 proximityparam = ( 474 ; the following is OPTIONAL, 475 ; and MAY occur more than once 477 (";" other-param) 479 ) 481 proximityvalue = "ARRIVE" / "DEPART" / 482 "CONNECT" / "DISCONNECT" / iana-token / x-name 484 8.2. Example 486 The following example shows a "VALARM" component with a proximity 487 trigger set to trigger when the device running the calendar user 488 agent leaves the vicinity defined by the structured location 489 property. Note use of the "u=" parameter with the "geo" URI to 490 define the precision of the location determination. 492 BEGIN:VALARM 493 UID:77D80D14-906B-4257-963F-85B1E734DBB6 494 TRIGGER;VALUE=DATE-TIME:19760401T005545Z 495 ACTION:DISPLAY 496 DESCRIPTION:Remember to buy milk 497 TRIGGER;VALUE=DATE-TIME:19760401T005545Z 498 PROXIMITY:DEPART 499 STRUCTURED-LOCATION;VALUE=URI:geo:40.443,-79.945;u=10 500 END:VALARM 502 9. Security Considerations 504 In addition to the security properties of iCalendar (see Section 7 of 505 [RFC5545]), VALARMs, if not monitored properly, can be used to "spam" 506 users and/or leak personal information. For instance, an unwanted 507 audio or display alert could be considered spam. Or an email alert 508 could be used to leak a user's location to a third party or to send 509 unsolicited email to multiple users. Therefore, CalDAV clients and 510 servers that accept iCalendar data from a third party (e.g. via iTIP 511 [RFC5546], a subscription feed, or a shared calendar) SHOULD remove 512 all VALARMs from the data prior to storing in their calendar system. 514 10. Privacy Considerations 516 Proximity VALARMs, if not used carefully, can leak a user's past, 517 present, or future location. For instance, storing an iCalendar 518 resource containing proxmity VALARMs to a shared calendar on CalDAV 519 server can expose to anyone that has access to that calendar the 520 user's intent to leave from or arrive at a particular location at 521 some future time. Furthermore, if a CalDAV client updates the shared 522 iCalendar resource with an ACKNOWLEDGED property when the alarm is 523 triggered, will leak the exact date and time that the user left from 524 or arrived at the location. Therefore, CalDAV clients that implement 525 proximity alarms SHOULD give users the option of storing and/or 526 acknowledging the alarms on the local device only and not storing the 527 alarm and/or acknowledgment on a remote server. 529 11. IANA Considerations 531 11.1. Property Registrations 533 This document defines the following new iCalendar properties to be 534 added to the registry defined in Section 8.2.3 of [RFC5545] and 535 located here: 537 +--------------+---------+----------------------+ 538 | Property | Status | Reference | 539 +--------------+---------+----------------------+ 540 | ACKNOWLEDGED | Current | RFCXXXX, Section 6.1 | 541 | PROXIMITY | Current | RFCXXXX, Section 8.1 | 542 +--------------+---------+----------------------+ 544 11.2. Relationship Types Registry 546 This document defines the following new iCalendar relationship type 547 to be added to the registry defined in Section 8.3.8 of [RFC5545] and 548 located here: 551 +-------------------+---------+----------------------+ 552 | Relationship Type | Status | Reference | 553 +-------------------+---------+----------------------+ 554 | SNOOZE | Current | RFCXXXX, Section 7.1 | 555 +-------------------+---------+----------------------+ 557 11.3. Proximity Value Registry 559 This document creates a new iCalendar registry for values of the 560 "PROXIMITY" property located here: 562 Additional values MAY be used, provided the process described in 563 Section 8.2.1 of [RFC5545] is used to register them, using the 564 template in Section 8.2.6 of [RFC5545]. 566 The following table has been used to initialize the Proximity Value 567 Registry. 569 +------------+---------+----------------------+ 570 | Value | Status | Reference | 571 +------------+---------+----------------------+ 572 | ARRIVE | Current | RFCXXXX, Section 8.1 | 573 | DEPART | Current | RFCXXXX, Section 8.1 | 574 | CONNECT | Current | RFCXXXX, Section 8.1 | 575 | DISCONNECT | Current | RFCXXXX, Section 8.1 | 576 +------------+---------+----------------------+ 578 12. Acknowledgments 580 This specification came about via discussions at the Calendaring and 581 Scheduling Consortium. Also, thanks to the following for providing 582 feedback: Bernard Desruisseaux, Mike Douglass, Jacob Farkas, Jeffrey 583 Harris, Ciny Joy, Barry Leiba, and Daniel Migault. 585 13. References 587 13.1. Normative References 589 [I-D.ietf-calext-eventpub-extensions] 590 Douglass, M., "Event Publishing Extensions to iCalendar", 591 draft-ietf-calext-eventpub-extensions-18 (work in 592 progress), January 2021. 594 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 595 Requirement Levels", BCP 14, RFC 2119, 596 DOI 10.17487/RFC2119, March 1997, 597 . 599 [RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault, 600 "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791, 601 DOI 10.17487/RFC4791, March 2007, 602 . 604 [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and 605 Scheduling Core Object Specification (iCalendar)", 606 RFC 5545, DOI 10.17487/RFC5545, September 2009, 607 . 609 [RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource 610 Identifier for Geographic Locations ('geo' URI)", 611 RFC 5870, DOI 10.17487/RFC5870, June 2010, 612 . 614 [RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986, 615 DOI 10.17487/RFC7986, October 2016, 616 . 618 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 619 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 620 May 2017, . 622 13.2. Informative References 624 [BTcore] Bluetooth Special Interest Group, "Bluetooth Core 625 Specification Version 5.0", December 2016, 626 . 629 [RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent 630 Interoperability Protocol (iTIP)", RFC 5546, 631 DOI 10.17487/RFC5546, December 2009, 632 . 634 Appendix A. Change History (To be removed by RFC Editor before 635 publication) 637 Changes in ietf-04: 639 1. Addressed security review comments from Valery Smyslov. 641 2. Addressed Genart review comments from Roni Even. 643 3. Added text addressing management of Proximity Value Registry. 645 Changes in ietf-03: 647 1. Fixed ABNF to be properly extended. 649 2. Addressed AD review comments from Barry Leiba. 651 Changes in ietf-02: 653 1. Addressed some WGLC comments from Daniel Migault. 655 Changes in ietf-01: 657 1. Reintroduced the RELATED-TO property for VALARMs and the SNOOZE 658 value for the RELTYPE property parameter. 660 2. Add Privacy Considerations section. 662 Changes in ietf-00: 664 1. Submitted as CALEXT draft. 666 Changes in daboo-05: 668 1. Added Murchison as editor. 670 2. Updated keywords boilerplate. 672 3. Added reference to UID security/privacy recommendations. 674 4. Removed default alarms. 676 5. Removed ALARM-AGENT property. 678 6. Added text about using TRIGGER value in the past in addition to 679 ACTION:NONE to have a default alarm be ignored. 681 7. Removed text about related alarms. 683 8. Removed URL alarm action. 685 9. Added reference to draft-ietf-calext-eventpub-extensions for 686 STRUCTURED-LOCATION. 688 10. Added CONNECT and DISCONNECT PROXIMITY property values. 690 11. Added Security Considerations. 692 12. Editorial fixes. 694 Changes in daboo-04: 696 1. Changed "ID" to "AGENT-ID". 698 2. Add more text on using "ACKNOWLEDGED" property. 700 3. Add "RELATED-TO" as a valid property for VALARMs. 702 4. Add "SNOOZE" relationship type for use with VALARMs. 704 5. State that "TRIGGER" is typically ignored in proximity alarms. 706 6. Added "PROXIMITY" value registry. 708 7. Added a lot more detail on default alarms including new action 709 and property. 711 Changes in daboo-03: none - resubmission of -02 713 Changes in daboo-02: 715 1. Updated to 5545 reference. 717 2. Clarified use of absolute trigger in UTC in snooze alarms 719 3. Snooze alarms should be removed when completed 721 4. Removed status and replaced last-triggered by acknowledged 722 property 724 5. Added location-based trigger 726 6. IANA registry tables added 728 Changes in daboo-01: 730 1. Removed DESCRIPTION as an allowed property in the URI alarm. 732 2. Added statement about what to do when ALARM-AGENT is not present. 734 3. Allow multiple ALARM-AGENT properties to be present. 736 4. Removed SNOOZE-UNTIL - snoozing now accomplished by creating a 737 new VALARM. 739 5. Remove VALARM by reference section. 741 6. Added more detail to CalDAV default alarms. 743 Authors' Addresses 745 Cyrus Daboo 746 Apple Inc. 747 1 Infinite Loop 748 Cupertino, CA 95014 749 USA 751 Email: cyrus@daboo.name 752 URI: http://www.apple.com/ 753 Kenneth Murchison (editor) 754 Fastmail US LLC 755 1429 Walnut St, Suite 1201 756 Philadephia, PA 19102 757 USA 759 Email: murch@fastmailteam.com 760 URI: http://www.fastmail.com/