LoST: A Location-to-Service Translation Protocol

Members of the IETF Emergency Context Resolution with Internet
Technologies (ECRIT) Working Group have published an updated Internet
Draft for the "LoST: A Location-to-Service Translation Protocol"
specification. The 77-page specification describes an XML-based protocol
for mapping service identifiers and geodetic or civic location
information to service contact URIs. In particular, it can be used to
determine the location-appropriate Public Safety Answering Point (PSAP)
for emergency services. Appendix A supplies a corresponding
non-normative RELAX NG Schema in XML Syntax. Protocols such as NAPTR
records and the Service Location Protocol (SLP) can be used to discover
servers offering a particular service. However, for an important class
of services the appropriate specific service instance depends both on
the identity of the service and the geographic location of the entity
that needs to reach it. Emergency telecommunications services are an
important example; here, the service instance is a Public Safety
Answering Point that has jurisdiction over the location of the user
making the call. The document describes a protocol for mapping a
service identifier and location information compatible with PIDF-LO
to one or more service URIs. Service identifiers take the form of the
service URNs; location information here includes revised civic location
information and a subset of the PIDL-LO profile which consequently
includes the Geo-Shapes defined for Geography Markup Language (GML).
Example service URI schemes include SIP, XMPP, and TEL. While the
initial focus is on providing mapping functions for emergency services,
it is likely that the protocol is applicable to other service URNs. For
example, in the United States, the "2-1-1" and "3-1-1" service numbers
follow a similar location-to- service behavior as emergency services.
LoST Satisfies the requirements for mapping protocols, providing a
number of operations, centered around mapping locations and service
URNs to service URLs and associated information. For civic addresses,
LoST can indicate which parts of the civic address are known to be
valid or invalid, thus providing address validation. LoST indicates
errors in the location data to facilitate debugging and proper user
feedback, but also provides best-effort answers. LoST queries can be
resolved recursively or iteratively.