Dynamic Extensions to the Presence Information Data Format Location Object (PIDF-LO)
Extracted elements (16)
Angular measures for <orientation> and <heading> are expressed relative to the presentity's current position using compass bearing from North (increasing toward East) to allow a single scalar representation that maps naturally to WGS 84 geodetic coordinates.
Rate-of-change information was added to PIDF-LO to enable applications to extrapolate positions between periodic location measurements and to support direct monitoring use cases such as verifying that a delivery vehicle observes speed limits.
Dynamic information can be safely ignored by a recipient that does not support this specification, enabling backward compatibility with existing PIDF-LO consumers.
Dynamic locations assume the same WGS 84 coordinate reference systems constrained by RFC 5491: either the 2D CRS 'urn:ogc:def:crs:EPSG::4326' (latitude, longitude) or the 3D CRS 'urn:ogc:def:crs:EPSG::4979' (latitude, longitude, altitude).
Dynamic information MAY be included in PIDF-LO without any other location information being present.
If two angular measures are present in an <orientation> or <heading> element, the values MUST be separated by whitespace.
When dynamic information is associated with information about the instantaneous position of the presentity, the <Dynamic> element MUST be included in the same <location-info> element as the corresponding geodetic or civic location information.
While a series of location snapshots already allows guessing future positions, explicitly including speed and heading in PIDF-LO makes future-location inference substantially easier. The privacy and security requirements of RFC 4119, RFC 3694, and RFC 3693 apply with greater urgency to documents carrying dynamic elements.
The <Dynamic> element is defined for conveying dynamic information about a moving presentity within PIDF-LO. It contains three optional child elements: <orientation>, <speed>, and <heading>, and is placed within the <location-info> element.
The <heading> element describes the directional component of velocity (direction of travel). It contains one or two angular values in degrees relative to current position; when only one angle is given, the associated <speed> contains only the horizontal speed component.
The <orientation> element describes the spatial orientation (direction of facing) of the presentity. It contains one or two angular values in degrees expressed relative to the current position, using the WGS 84 CRS.
The <speed> element carries the scalar time rate of change in position (speed without regard to direction). Values are expressed in meters per second as an xs:double.
This document registers a new XML namespace 'urn:ietf:params:xml:ns:pidf:geopriv10:dynamic' in the IETF XML Registry (RFC 3688) for the dynamic feature extensions to PIDF-LO.
This document registers a new XML schema under URI 'urn:ietf:params:xml:schema:pidf:dynamic' in the IETF XML Registry (RFC 3688), corresponding to the schema defined in Section 4.
Dynamic location information increases the severity of an information leak compared to static snapshots because attackers can use velocity, heading, and orientation data to anticipate the future location of a presentity. Deployers are strongly advised to provide users with access control mechanisms over location distribution.
The <Dynamic> element is defined by the XML schema at namespace 'urn:ietf:params:xml:ns:pidf:geopriv10:dynamic'. It uses a dynamicType complex type with optional orientation, speed (xs:double), and heading child elements. The directionType is a whitespace-separated list of one or two xs:double values.