GEOPRIV R. Mahy
Internet-Draft Plantronics
Intended status: Standards Track B. Rosen, Ed.
Expires: March 19, 2010 NeuStar
H. Tschofenig
Nokia Siemens Networks
September 15, 2009
A Document Format for Filtering and Reporting Location Notications in
the Presence Information Document Format Location Object (PIDF-LO)
draft-ietf-geopriv-loc-filters-06.txt
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Abstract
This document describes filters that limit asynchronous location
notifications to compelling events, designed as an extension to RFC
4661 "An XML-Based Format for Event Notification Filtering". The
resulting location information is conveyed in existing location
formats wrapped in the Presence Information Document Format
(PIDF-LO).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Filter Definitions . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Movement . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Speed Changes . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Element Value Changes . . . . . . . . . . . . . . . . . . 6
3.4. Entering or Exiting a Region . . . . . . . . . . . . . . . 6
3.5. Location Type . . . . . . . . . . . . . . . . . . . . . . 8
3.6. Rate Control . . . . . . . . . . . . . . . . . . . . . . . 10
4. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:location-filter . . . . . . . . . . 15
6.2. Schema Registration For location-filter . . . . . . . . . 15
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informational References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
Conveying location information encapsulated with a PIDF-LO [RFC4119]
document within SIP is described in
[I-D.ietf-sipcore-location-conveyance]. An alternative signaling
approach, which uses asynchronous communication, is available with
the SIP event notification mechanisms (see RFC 3265 [RFC3265]) and is
used by this document. Unfortunately, it is more complex since many
forms of location are measured as a continuous gradient. Unlike
notifications using discret quantities, it is difficult to know when
a change in location is large enough to warrant a notification. RFC
3265 can be used with so-called 'filters' (see RFC 4661 [RFC4661])
that allow the number of notifications to be reduced. The mechanism
described in this document defines an extension to RFC 4661
[RFC4661], which limits location notification to events that are of
relevance to the subscriber. These filters persist until they are
changed with a replacement filter.
The frequency of notifications necessary for various geographic
location applications varies dramatically. The subscriber should be
able to get asynchronous notifications with appropriate frequency and
granularity, without having to issue a large number of notifications
that are not important to the application.
This document defines the following list of events that may be
relevant to a subscriber:
1. the Device moves more than a specified distance since the last
notification
2. the Device exceeds a specified speed
3. the Device enters or exits a region (described by a circle or a
polygon)
4. one or more of the values of the specified address labels have
changed for the location of the Device. For example, the value
of the <A1> civic address element has changed from 'California'
to 'Nevada'.
5. the type of location information being requested.
6. the rate at which location information delivery is desired.
This document builds on the presence event package' [RFC3856], i.e.
an existing event package for communicating location information
inside the PIDF-LO.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
This document reuses terminology from [I-D.ietf-geopriv-arch].
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3. Filter Definitions
3.1. Movement
The <moved> element with a value in meters indicates the minimum
distance that the resource must have moved from the location of the
resource when the last notification was sent in order to trigger this
event. The distance is measured in meters absolutely from the point
of last notification rather than in terms of cumulative motion. The
<moved> element MUST only appear once as a child element of <filter>.
<?xml version="1.0" encoding="UTF-8"?>
<filter-set
xmlns="urn:ietf:params:xml:ns:simple-filter"
xmlns:ext="urn:ietf:params:xml:ns:location-filter">
<filter id="123" uri="sip:presentity@example.com">
<ext:moved>300</ext:moved>
</filter>
</filter-set>
Figure 1: Movement Filter Example
3.2. Speed Changes
Speed changes can be filtered with the help of RFC 4661 and the
functionality provided in [I-D.singh-geopriv-pidf-lo-dynamic], which
extends the PIDF-LO with support for spatial orientation, speed,
heading, and acceleration.
Figure 2 shows an example for a trigger that fires when the speed of
the Target changes by 3 meters per second.
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<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="dyn"
urn="urn:ietf:params:xml:schema:pidf:dynamic"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@example.com">
<trigger>
<changed by="3">
//dyn:speed
</changed>
</trigger>
</filter>
</filter-set>
Figure 2: Speed Change Example
3.3. Element Value Changes
Changes in values, for example related to civic location information,
can be provided by the base functionality offered with RFC 4661.
Figure 3 shows an example where a notification is sent when the civic
address tokens A1, A2, A3, or PC change.
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="ca"
urn="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@example.com">
<trigger>
<changed>//ca:A1</changed>
<changed>//ca:A2</changed>
<changed>//ca:A3</changed>
<changed>//ca:PC</changed>
</trigger>
</filter>
</filter-set>
Figure 3: Speed Change Example
3.4. Entering or Exiting a Region
The <enterOrExit> condition is satisfied when the Target enters or
exits a named 2-dimensional region described by a polygon (as defined
in Section 5.2.2 of [RFC5491]), or a circle (as defined in Section
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5.2.3 of [RFC5491]).
Figure 4 shows filter examples whereby a notification is sent when
the Target enters or exits an area described by a circle and Figure 5
describes an area using a polygon.
<?xml version="1.0" encoding="UTF-8"?>
<filter-set
xmlns="urn:ietf:params:xml:ns:simple-filter"
xmlns:ext="urn:ietf:params:xml:ns:location-filter"
xmlns:gml="http://www.opengis.net/gml"
xmlns:gs="http://www.opengis.net/pidflo/1.0">
<filter id="123" uri="sip:presentity@example.com">
<ext:enterOrExit>
<gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>42.5463 -73.2512</gml:pos>
<gs:radius uom="urn:ogc:def:uom:EPSG::9001">
850.24
</gs:radius>
</gs:Circle>
</ext:enterOrExit>
</filter>
</filter-set>
Figure 4: <enterOrExit> Circle Filter Example
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<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter"
xmlns:ext="urn:ietf:params:xml:ns:location-filter"
xmlns:gml="http://www.opengis.net/gml">
<filter id="123" uri="sip:presentity@example.com">
<ext:enterOrExit>
<gml:Polygon srsName="urn:ogc:def:crs:EPSG::4326">
<gml:exterior>
<gml:LinearRing>
<gml:posList>
43.311 -73.422 43.111 -73.322
43.111 -73.222 43.311 -73.122
43.411 -73.222 43.411 -73.322
43.311 -73.422
</gml:posList>
</gml:LinearRing>
</gml:exterior>
</gml:Polygon>
</ext:enterOrExit>
</filter>
</filter-set>
Figure 5: <enterOrExit> Polygon Filter Example
3.5. Location Type
The <locationType> element MAY be included as a child element of the
<filter> element and it contains a list of location information types
that are requested by the subscriber. The following list describes
the possible values:
any: The Notifier SHOULD attempt to provide LI in all forms
available to it.
geodetic: The Notifier SHOULD return a location by value in the form
of a geodetic location.
civic: The Notifier SHOULD return a location by value in the form of
a civic address.
The Notifier SHOULD return the requested location type or types. The
location types the LIS returns also depend on the setting of the
optional "exact" attribute. If the 'exact' attribute is set to
"true" then the Notifier MUST return either the requested location
type or provide an error response. The 'exact' attribute does not
apply (is ignored) for a request for a location type of "any".
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In the case of a request for specific locationType(s) and the 'exact'
attribute is false, the Notifier MAY provide additional location
types, or it MAY provide alternative types if the request cannot be
satisfied for a requested location type. The "SHOULD"-strength
requirements on this parameter for specific location types are
included to allow for soft-failover.
If the <locationType> element is absent, a value of "any" MUST be
assumed as the default.
The Notifier SHOULD provide location in the response in the same
order in which they were included in the "locationType" element in
the request. Indeed, the primary advantage of including specific
location types in a request when the 'exact' attribute is set to
"false" is to ensure that one receives the available locations in a
specific order. For example, a subscription for "civic" (with the
'exact' attribute set to "false") could yield any of the following
location types in the response:
o civic
o civic, geodetic
o geodetic (only if civic is not available)
For the example above, if the 'exact' attribute was "true", then the
only possible response is either a "civic" location or an error
message.
As stated above, the <locationType> element MAY carry the 'exact'
attribute. When the 'exact' attribute is set to "true", it indicates
to the Notifier that the contents of the <locationType> element MUST
be strictly followed. The default value of "false" allows the
Notifier the option of returning something beyond what is specified,
such as a set of location URIs when only a civic location was
requested. A value of "true" indicates that the Notifier MUST
provide a location of the requested type or types or MUST provide an
error.
An example is shown in Figure 6 that utilizes the <locationType>
element with the 'exact' and the 'responseTime' attribute.
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<?xml version="1.0" encoding="UTF-8"?>
<filter-set
xmlns="urn:ietf:params:xml:ns:simple-filter"
xmlns:ext="urn:ietf:params:xml:ns:location-filter">
<filter id="123" uri="sip:presentity@example.com">
<ext:locationType exact="true">
geodetic
</ext:locationType>
</filter>
</filter-set>
Figure 6: <locationType> Filter Example
3.6. Rate Control
[I-D.ietf-sipcore-event-rate-control] defines an extension to the SIP
events framework defining the following three "Event" header field
parameters that allow a subscriber to set a minimum, a maximum and an
average rate of event notifications generated by the notifier. This
document makes use of two of the parameters to accomplish
functionality equivalent to the 'responseTime' attribute used in HELD
[I-D.ietf-geopriv-http-location-delivery], namely "min-interval"
(which specifies a minimum notification time period between two
notifications, in seconds) and "max-interval" (which specifies a
maximum notification time period between two notifications, in
seconds.). Whenever the time since the most recent notification
exceeds the value in the "max-interval" parameter, then the current
state would be sent in its entirety, just like after a subscription
refresh.
If complete state is not immediately available, a NOTIFY containing
state (i.e. location) is generated some time between the time
included in 'min-interval' and the time in 'max-interval'. An
important use case for location based applications focuses on the
behavior of the initial NOTIFY message(s) and the information it
returns, for example in case of emergency call routing. When an
initial NOTIFY is transmitted it might not include complete state.
Subscriber Notifier
|---SUBSCRIBE(1)--->| Request state subscription
|<-------200--------| Acknowledge subscription
|<-----NOTIFY(2)----| Return current state information
|-------200(3)----->|
|<-----NOTIFY(4)----| Return current state information
|--------200------->|
Figure 7: SUBSCRIBE/NOTIFY with Rate Control
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Figure 7 shows a SUBSCRIBE/NOTIFY exchange. The initial SUBSCRIBE
message (1) has filters attached and contains a 'max-interval' rate
control parameter. In certain situations it is important to obtain
some amount of location information within a relatively short and
pre-defined period of time even if the obtained location information
contains a high amount of uncertainty and location information withy
less uncertainty at a later point in time. An example is emergency
call routing where a emergency services routing proxy may need to
obtain location information suitable for routing rather quickly and
subsequently a Public Safety Answering Point requests location
information for dispatch. To obtain location information in a timely
fashion using the SUBSCRIBE/NOTIFY mechanism, it is RECOMMENDED that
the initial SUBSCRIBE contains a 'max-interval' rate control
parameter (with a small value) that is in a later message updated to
a more sensible value. The 'max-interval' for this first request is
therefore much lower than thereafter. Updating the 'max-interval'
for the subscription can be performed in the 200 response (see
message 3) to the NOTIFY that contains state. Depending on the value
in the 'max-interval' parameter the Notifier may create a NOTIFY
message (see message 2) immediately in response to the SUBSCRIBE that
might be empty in case no location information is available at this
point in time. The desired location information may then arrive in
the subsequent NOTIFY message (see message 4).
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4. XML Schema
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
targetNamespace="urn:ietf:params:xml:ns:location-filter"
xmlns:filter="urn:ietf:params:xml:ns:location-filter"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:gml="http://www.opengis.net/gml">
<!-- These elements are child elements of the RFC 4661
<filter> element.
-->
<xs:element name="enterOrExit" type="gml:GeometryPropertyType"/>
<xs:element name="moved" type="filter:movedType"/>
<xs:complexType name="movedType">
<xs:simpleContent>
<xs:extension base="xs:double">
<xs:anyAttribute namespace="##any" processContents="lax"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
<xs:element name="locationType" type="filter:locationTypeType"/>
<xs:simpleType name="locationTypeBase">
<xs:union>
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:enumeration value="any"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType>
<xs:restriction base="filter:locationTypeList">
<xs:minLength value="1"/>
</xs:restriction>
</xs:simpleType>
</xs:union>
</xs:simpleType>
<xs:simpleType name="locationTypeList">
<xs:list>
<xs:simpleType>
<xs:restriction base="xs:token">
<xs:enumeration value="civic"/>
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<xs:enumeration value="geodetic"/>
</xs:restriction>
</xs:simpleType>
</xs:list>
</xs:simpleType>
<xs:complexType name="locationTypeType">
<xs:simpleContent>
<xs:extension base="filter:locationTypeBase">
<xs:attribute name="exact" type="xs:boolean"
use="optional" default="false"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:schema>
Figure 8: XML Schema
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5. Security Considerations
This document builds on a number of specifications, namely
o the SIP event notification mechanism, described in RFC 3265
[RFC3265], defining the SUBSCRIBE/NOTIFY messages.
o the presence event package, described in RFC 3856 [RFC3856], which
is a concrete instantiation of the general event notification
framework.
o PIDF-LO, described in RFC 4119 [RFC4119], as the XML container
that carries location information. PIDF payloads are exchanged
via the presence event package and the location object extension
of it provides the necessary functionality for this document.
o the filter framework, described in RFC 4661 [RFC4661], to offer
the ability to reduce the amount of notifications being sent.
Each of these documents listed above comes with a security
consideration section but the security and privacy aspects are best
covered by the SIP presence event package, see Section 9 of
[RFC3856], and with the GEOPRIV architectural description found in
[I-D.ietf-geopriv-arch]. The functionality for uploading
authorization policies and other information that limit access to
location information are provided by other protocols, such Common
Policy [RFC4745], Geolocation Policy [I-D.ietf-geopriv-policy] or
more recent work around HELD context
[I-D.winterbottom-geopriv-held-context]. The functionality described
in this document extends the filter framework with location specific
filters. Local policies might be associated with the usage of
certain filter constructs and with the amount of notifications
specific filter settings might cause.
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6. IANA Considerations
6.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:location-filter
This section registers a new XML namespace, as per the guidelines in
[RFC3688].
URI: urn:ietf:params:xml:ns:location-filter
Registrant Contact: IETF, GEOPRIV working group, <geopriv@ietf.org>,
as delegated by the IESG <iesg@ietf.org>.
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Location Filter Namespace</title>
</head>
<body>
<h1>Namespace for PIDF-LO Location Filters</h1>
<h2>urn:ietf:params:xml:ns:location-filter</h2>
<p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
</body>
</html>
END
6.2. Schema Registration For location-filter
This specification registers a schema, as per the guidelines in
[RFC3688].
URI: urn:ietf:params:xml:schema:location-filter
Registrant Contact: IETF, GEOPRIV Working Group
(geopriv@ietf.org), as delegated by the IESG (iesg@ietf.org).
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XML: The XML can be found as the sole content of Section 4.
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7. Contributors
We would like to thank Martin Thomson and James Polk for their
contributions to this document.
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8. Acknowledgments
Thanks to Richard Barnes and Alissa Cooper, Adam Roach, Allan
Thomson, James Winterbottom for their comments.
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9. References
9.1. Normative References
[GML] OpenGIS, "Open Geography Markup Language (GML)
Implementation Specification", OpenGIS OGC 02-023r4,
January 2003,
<http://www.opengis.org/techno/implementation.htm>.
[I-D.ietf-geopriv-arch]
Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
Tschofenig, H., and H. Schulzrinne, "An Architecture for
Location and Location Privacy in Internet Applications",
draft-ietf-geopriv-arch-00 (work in progress), July 2009.
[I-D.ietf-sipcore-event-rate-control]
Niemi, A., Kiss, K., and S. Loreto, "Session Initiation
Protocol (SIP) Event Notification Extension for
Notification Rate Control",
draft-ietf-sipcore-event-rate-control-00 (work in
progress), May 2009.
[I-D.singh-geopriv-pidf-lo-dynamic]
Schulzrinne, H., Singh, V., Tschofenig, H., and M.
Thomson, "Dynamic Extensions to the Presence Information
Data Format Location Object (PIDF-LO)",
draft-singh-geopriv-pidf-lo-dynamic-07 (work in progress),
August 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3856] Rosenberg, J., "A Presence Event Package for the Session
Initiation Protocol (SIP)", RFC 3856, August 2004.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", BCP 13, RFC 4288, December 2005.
[RFC4661] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa-
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Requena, "An Extensible Markup Language (XML)-Based Format
for Event Notification Filtering", RFC 4661,
September 2006.
[RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV
Presence Information Data Format Location Object (PIDF-LO)
Usage Clarification, Considerations, and Recommendations",
RFC 5491, March 2009.
9.2. Informational References
[I-D.ietf-geopriv-http-location-delivery]
Barnes, M., Winterbottom, J., Thomson, M., and B. Stark,
"HTTP Enabled Location Delivery (HELD)",
draft-ietf-geopriv-http-location-delivery-16 (work in
progress), August 2009.
[I-D.ietf-geopriv-policy]
Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
and J. Polk, "Geolocation Policy: A Document Format for
Expressing Privacy Preferences for Location Information",
draft-ietf-geopriv-policy-21 (work in progress),
July 2009.
[I-D.ietf-sipcore-location-conveyance]
Polk, J. and B. Rosen, "Location Conveyance for the
Session Initiation Protocol",
draft-ietf-sipcore-location-conveyance-01 (work in
progress), July 2009.
[I-D.winterbottom-geopriv-held-context]
Winterbottom, J., Tschofenig, H., and M. Thomson,
"Establishing Location URI Contexts using HTTP-Enabled
Location Delivery (HELD)",
draft-winterbottom-geopriv-held-context-04 (work in
progress), April 2009.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
Polk, J., and J. Rosenberg, "Common Policy: A Document
Format for Expressing Privacy Preferences", RFC 4745,
February 2007.
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Authors' Addresses
Rohan Mahy
Plantronics
345 Encincal Street
Santa Cruz, CA
USA
Email: rohan@ekabal.com
Brian Rosen (editor)
NeuStar
470 Conrad Dr.
Mars, PA 16046
US
Phone: +1 724 382 1051
Email: br@brianrosen.net
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Mahy, et al. Expires March 19, 2010 [Page 21]
