Proposal:

Location for Atom Syndication

Abstract:

This document specifies the minimal, fundamental representation of spatial location within Atom [1] feeds and entries.

Introduction:

Joshua Lieberman suggested "Ground State for Atom" as a name for this work. "Ground" resonates well with "geography", but the original German "grund" means fundamental -- this proposal aims to be a fundamental, minimal specification for location in Atom, relying on, and consistent with, other Atom and AtomPub extensions [2,3] wherever possible, with a minimum of invention. (Author's note: think "n=1".)

Examples:

   <?xml version="1.0" encoding="utf-8"?>
   <feed
     xmlns="http://www.w3.org/2005/Atom"
     xmlns:georss="http://www.georss.org/georss"
     xmlns:gml="http://www.opengis.net/gml"
     >

     <title>Example Feed</title>
     <link href="http://example.org/"/>
     <updated>2003-12-13T18:30:02Z</updated>
     <author>
       <name>John Doe</name>
     </author>
     <id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>

     <entry>
       <title>Atom-Powered Robots Run Amok</title>
       <link href="http://example.org/2003/12/13/atom03"/>
       <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
       <updated>2003-12-13T18:30:02Z</updated>
       <summary>Some text.</summary>
       
       <georss:where>
         <gml:Point>
           <gml:pos>40.5 -105.8</gml:pos>
         </gml:Point>
       </georss:where>

     </entry>

   </feed>

Notation Conventions:

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 BCP 14, [RFC2119], as scoped to those conformance targets.

The XML Namespaces URIs [W3C.REC-xml-names-19990114] for the XML elements and attributes described in this specification are:

http://www.georss.org/georss and http://www.opengis.net/gml

In this document, the namespace prefix "georss:" is used for the http://www.georss.org/georss Namespace URI, "gml:" is used for the http://www.opengis.net/gml Namespace URI. Note that the choice of namespace prefix is arbitrary and not semantically significant.

The text of this specification provides the sole definition of conformance.

The "georss:where" Extension Element:

The "georss:where" element conveys spatial location for an entry. To Atom, it is a structured extension element [4]. The element SHALL contain a GML "simple features profile" geometry [5].

Cardinality: An Atom entry or feed SHALL have 0-1 "georss:where" elements.

Links to Locations:

Under debate in another thread ...

Relationship to GeoRSS 1.0:

This specification will be compatible with the geometry encoding aspect of GeoRSS 1.0 (the bulk of that spec). GeoRSS 1.0 elements "elev", "radius" (obviated by use of GML), "floor", "featurename", and "featuretypetag" (level n>1 features) SHALL be omitted.

Security Considerations:

As this specification defines an extension to the Atom Syndication Format, it is subject to the same security considerations defined in [RFC4287].

(Though if we add links to location to this specification, there will be some considerations similar to those in RFC 4685 and 4946.)

IANA Considerations:

None.

Acknowledgements:

Some portions of text in this document have been adapted from
[RFC4287] and [RFC4685] in order to maintain a stylistic and technical alignment with that specification.

Author's Address:

Sean Gillies

EMail: sean.gillies@gmail.com
URI: http://zcologia.com/sgillies

Normative References:

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", http://tools.ietf.org/html/bcp14, http://tools.ietf.org/html/rfc2119, March 1997.

[W3C.REC-xml-names-19990114] Hollander, D., Bray, T., and A. Layman, "Namespaces in XML", W3C REC REC-xml-names-19990114, January 1999.

[RFC4287] Nottingham, M. and R. Sayre, "The Atom Syndication Format", RFC 4287, December 2005.

[RFC4685] Snell, J., "Atom Threading Extension", http://tools.ietf.org/html/rfc4685, September 2006.

References:

[1] Atom Syndication Format: http://tools.ietf.org/html/rfc4287
[2] Atom Threading Extension: http://tools.ietf.org/html/rfc4685
[3] Atom License Extension: http://tools.ietf.org/html/rfc4946
[4] Structured Extension Elements: http://tools.ietf.org/html/rfc4287#section-6.4.2
[5] GMLSF: http://portal.opengeospatial.org/files/?artifact_id=15201