GeoRSS and its relation to the SEMANTIC WEB Sanjay Gangaiah Sathwik Ramaswamy

Introduction  GeoRSS is simple proposal for geo-enabling, or tagging, "really simple syndication" (RSS) feeds with location information.  GeoRSS proposes a standardized way in which location is encoded with enough simplicity and descriptive power to satisfy most needs to describe the location of Web content.  GeoRSS is also intended to be a lightweight way to express geography in other XML-based formats – including XHTML.

Practical example: A Geo RSS feed populates ACMEs GeoRSS Map Viewer with State Parks in California (Mapufacture)

What is RSS ? RSS is a family of XML formats for exchanging news, especially news about Web pages or other Web content. Many dynamic web sites, especially "Blogs" now provide RSS "feeds" of their new or changed content. RSS is a simple, brief, and structured XML format Includes key descriptive elements like author, date, title, narrative description, and hypertext link, elements Helps the reader decide what source materials are worth examining in more detail. This concise, structured format has also proven useful for publishing all kinds of small, time-sensitive nuggets of information, including Flickr's photo journals, Craigslist classifieds, and local events.

Atom 1.0 Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (APP for short) is a simple HTTP-based protocol for creating and updating Web resources. Web feeds allow software programs to check for updates published on a web site. The feed can then be downloaded by web sites that syndicate content from the feed, or by feed reader programs that allow Internet users to subscribe to feeds and view their content. A feed contains entries, which may be headlines, full-text articles, excerpts, summaries, and/or links to content on a web site, along with various metadata. Web feeds are designed to be machine-readable rather than human- readable, which tends to be a source of confusion when people first encounter web feeds. This means that web feeds can also be used to automatically transfer information from one website to another, without any human intervention.

Why Geo RSS ?  Location needs to be described in an inter operable manner so that applications can Request Aggregate Share Map geographically tagged feeds.  It achieves upward compatibility across encodings.  Useful in the possibilities for geographic search and aggregation.

GeoRSS UML Model

GeoRSS Encodings GeoRSS has two encodings GeoRSS GML Geography Markup Language (GML) is an XML grammar written in XML Schema for the modelling, transport, and storage of geographic information. GML provides a variety of kinds of objects for describing geography including features, coordinate reference systems, geometry, topology, time, units of measure and generalized values. GeoRSS GML is a formal GML Application Profile, and supports a greater range of features than Simple, notably coordinate reference systems other than WGS84 latitude/longitude. It is designed for use with Atom 1.0, RSS 2.0 and RSS 1.0, although it can be used just as easily in non-RSS XML encodings. GeoRSS Simple has greater brevity, but also has limited extensibility. It can be used in all the same ways and places as GeoRSS GML. GeoRSS Simple The Simple serialization of GeoRSS is designed to be maximally concise, in both Srepresentation and conception. Each of the four GeoRSS objects require only a single tag. This simplicity comes at the cost of direct upward compatibility with GML. However, it is straightforward to devise transformations from this Simple serialization to the GML serialization through the GML model.

GeoRSS Concept GeoRSS itself is identified by a namespace, indicated by "georss:". The Geo RSS model must be expressed in a concrete form such as XML, RDF The core concepts of GeoRSS: CRS Geometry Tags Elevation

Coordinate Reference System (CRS) There aren't real grid lines or axes on the earth Any GeoRSS coordinates must refer to a coordinate reference system which has been defined and agreed to by geodesists and software makers alike. The GeoRSS CRS is the global (and GPS-preferred) WGS84 (World Geodetic system), latitude, longitude (in that order), using decimal degrees. GeoRSS lines and boundaries are allowed to do things like cross the dateline or circle the poles.

Geometry The geometric shapes which can be used to represent location in GeoRSS are: Point contains a single coordinate pair. The coordinate pair contains a latitude value and a longitude value in that order. Line contains two or more coordinate pairs. Each pair contains a latitude value and a longitude value in that order. Pairs are separated from each other by a space. Box contains exactly two coordinate pairs. Each pair contains a latitude value and a longitude value in that order. Pairs are separated from each other by a space. The first coordinate pair (lower corner) must be a point further west and south of the second coordinate pair (upper corner) and the box is always interpreted as not containing the 180 (or -180) degree longitude line other than on its boundary and not containing the North or South pole other than on its boundary.

Polygon contains at least four coordinate pairs. Each pair contains a latitude value and a longitude value in that order. The last coordinate pair must be identical to the first.

Tags There are 2 types Feature Type Tag GeoRSS geometry is meant to represent a real feature of the Earth's surface. The GeoRSS model allows for a single string containing a featuretypetag. No constraints are placed on this string. The intent is to allow a Feature Type folksonomy to emerge. The default is "location". Relationship Tag GeoRSS is a way of relating Web content to Earth features. The GeoRSS model allows for a single string containing a relationshiptag. No constraints are placed on this string. The intent is to allow a relationship folksonomy to emerge.The default relationship, "is-located-at" simply indicates that the subject of the content is located at the GeoRSS feature.

Elevation Expresses an elevation; GeoRSS Simple has two special tags. These tags are not meant to be used in the GML version since elevation values would be properly expressed based in more precise terms. The tags are elev and floor. elev is meant to contain "common" GPS elevation readings, i.e. height in meters from the WGS84 ellipsoid, which is a reading that should be easy to get from any GPS device. floor is meant to contain the floor number of a building. In some countries the numbering is different than in other countries, but since we'll know the location of the building, it should be fairly unambiguous.

GeoRSS in RDF In the RDF framework, the content and meaning of Simple GeoRSS can be stated in a few words: georss:point georss:line georss:polygon georss:box Each property has a string literal as value, with the detailed forms as explained on the Simple GeoRSS page. Asserting that the value of the property georss:point for an object A is "lat,long" means that the geographical location with these coordinates is associated with A. The nature of the association is left unspecified.

GeoRSS in RDF: Usage M 3.2, Mona Passage urn:uuid:1225c695-cfb8-4ebb-aaaa- 80da344efa6a T07:02:32Z We just had a big one

GeoRSS in RDF: Usage..contd city is-centered- at

GeoRSS in RDF Similarly, the properties georss:line, georss:polygon, and georss:box, assert the existence of associated earth-located geometries. These properties can be used in any RDF context to make simple geographical assertions about objects. However, there is nothing special about how GeoRSS properties are used in RSS we need only note that any of the RSS 1.0 elements can be annotated with GeoRSS properties, including rss:channel, rss:item, and rss:image.

GeoRDF example (Boat trip) Dino's Mt. Washington trip T18:30:02Z Calvin Setting off

GeoRDF example…contd T07:02:32Z getting ready to take the mountain! Crossing Muddy Creek T07:02:32Z Check out the salamanders here

GeoRDF example(Point) M 3.2, Mona Passage urn:uuid:1225c695-cfb8-4ebb-aaaa- 80da344efa6a We just had a big one

GeoRDF example(Line)

GeoRDF example(Polygon)

Relationship of GeoRSS GML and GML The GeoRSS GML encodings are very similar to what a formal GML profile would be. A Point geometry is expressed as follows: As can be seen, the GeoRSS GML encoding for a point is very similar to a full GML structure. However, in GeoRSS the assumption is made that the default CRS is WGS 84 lat/long 2d. This really simplifies the encoding and the ability of “hackers” to understand and implement GeoRSS.

Applications of Geo RSS  Perhaps, the most powerful advantages of GeoRSS feeds will be seen in the possibilities for geographic search and aggregation.  More than just getting feeds for a particular city or zip code, using GeoRSS, it will be posssible to search with all sorts of geographic criteria like - all earthquake-related items within 20 miles of your home. a feed of traffic accident items along your daily commute.  Once RSS feeds contain geographic location, applications like these and more will be possible.

GeoRSS : The History Dave Winer "plays around" with web feeds RSS “invented” – Netscape RSS v 0.9 released 1999 April - geotags.com registered by Andrew Daviel of Richmond, BC, Canada 2001: Internet draft submitted to the IETF for Geo-registration (geotagging) of HTML documents, Kaegi and Daviel. Never became a standard but significant because it appears to build on the iCalander syntax but is much richer and more semantically rigorous 2002: GeoURL concept established - geotagging of URL locations January: First version of the W3C "geo" vocabulary/syntax published. geo is a simple micro-format (RDF based) for geo-tagging web content using a point geometry May. First known instance of the use of the term "georss".

GeoRSS History… contd 2003 July: Harvard releases 2005 July. Raj Singh, Josh Lieberman, and Allan Doyle decided to go for georss. Raj Singh registers the georss.org domain on 7/20/2005. This could be considered the official start date of the current georss initiative. Allan Doyle sets up the georss server on an eogeo machine over the next couple of days August: All this discussion led to an August 18th teleconference to have a brainstorming session that included Allan Doyle, Josh Lieberman, Raj Singh, Ron Lake, and Carl Reed. There were series of teleconferences and s January: May be the first official version of this flavor of GeoRSS, ready for implementation.

Examples of GeoRSS implementations Explore-Our-Planet6 Planet6 GeoRSS feed reader users can read, listen and view latest news on the map and use links to mentioned places. The geofeed Explorer displays colored icons for each news entry. All sources have their individual color and icons and news entries are linked. Some examples on proper usage for feeds are listed in the post: interesting-rss-feeds-for-geotagging.html. There is a list for all users with exciting RSS channels, registered users define their favorites in the extended profile editor. Much of the data processing is done at geonames.org.

Explore-Our-Planet6

The Geonames "RSS to GeoRSS Converter" reads the entries of an RSS feed and searches the Geonames Database to find a location for the entry text. If a relevant location is found, its latitude and longitude are added to the RSS feed using the GeoRSS encoding. It works for any RSS feed, just pass the feed URL as a parameter to the converter and your feed entries will get latitude and longitude in real time. Geo-Names.org

USGS USGS publishes GeoRSS earthquake alerts. Following the Asian Tsunami, the Joint Research Centre at the European Commission built a real time tsunami alert system, by triggering an online tsunami simulation based on USGS published earthquake events, then publishing the results for subscription and visualization in GeoRSS. They use GeoRSS, with the addition of their own domain specific extensions. RSS is simply the fastest way to carry out their crucial work.

USGS

TripTracker TripTracker8 is used for creating and sharing travel journals. GPS track logs can be imported to automatically geotag photos; nearby photos are also grouped into geocoded trip entries. Trips are presented using a JavaScript map interface (similar to Google Maps, but with richer photo presentations). These maps render an Atom feed containing GeoRSS GML. TripTracker uses tags to present locations of trip entries and photos. They also use tags to render GPS track logs.

TripTracker And the resulting map:

GeoTagging GeoTagging, sometimes referred to as Geocoding, is the process of adding geographical identification metadata to various media such as websites, RSS feeds, or images. This data usually consists of latitude and longitude coordinates, though it can also include altitude and place names. Geocoding also refers to the process of taking non-coordinate based geographical identifiers, such as a postal address, and converting them into geographic coordinates. GeoTagging can help users find a wide variety of location-specific information. GeoTagging-enabled information services can also potentially be used to find news, websites, or other resources.

Basic Geo (WGS84 lat/long) Vocabulary The basic RDF vocabulary provides the Semantic Web community with a namespace for representing lat(itude), long(itude) and other information about spatially-located things, using WGS84 as a reference datum. The vocabulary is getting significant usage, both (as intended) within RDF documents, but also as a namespace used within non-RDF XML documents, such as RSS 2.0. This vocabulary begins an exploration of the possibilities of representing mapping/location data in RDF, and does not attempt to address many of the issues covered in the professional GIS world, notably by the Open Geospatial Consortium (OGC). Instead, a few basic terms are used in RDF when there is a need to describe latitudes and longitudes. The motivation for using RDF as a carrier for lat/long info is RDF's capability for cross-domain data mixing. We can describe not only maps, but the entities that are positioned on the map. And we can use any relevant RDF vocabularies to do so, without the need for expensive pre-coordination, or for changes to a centrally maintained schema.

A standalone example:

Database Tools of the Future? "The Two-Way Data Web". Atom and RSS web feed formats have already been used to create blog databases, and "Atom and RSS are evolving into tools for creating loosely-coupled databases on Internet scale." We could write a PHP or Perl script that parses an XML feed, then check the incoming URL's parameter string to determine what operation to perform. Let vendors know that we have the tools, for both end users as well as programmers, to read and write GeoRSS.

References: [1] OGC White Paper, An Introduction to GeoRSS: A Standards Based Approach for Geo-enabling RSS feeds. [2] podcasts.html [3] [4] [5] [6] [7] [8] [9] OGC Abstract Specification Topic 2, Spatial referencing by coordinates, Roger Lott