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Datacasting XML Feed Specification

Overview

Datacasting feeds conform to the RSS 2.0 standard. We also use extensions from the geoRSS namespace and have developed a Datacasting namespace. The specifics of the Datacasting feed standard are described in the chart below.

The value of a Datacasting Feed is dependent on the quality of the metadata associated with the feed and each item. In addition to the standard tags below, the publisher can create customElement tags describing the data. CustomElement tags can be used to communicate summary data or to call out the location of a feature of interest in the data. The metadata associated with the feed and its items is used by the Datacasting Feed Reader to filter, download and visualize the data.

When developing a Datacasting feed, think about the users of the data that you are publishing. What metadata will help them decide which data is of use to them?


XML Elements

Required Channel Elements
Element Description Namespace Example
title Title of the entire RSS feed RSS2.0 AVHRR Sea Surface Temerature at 4km
link A link to the site for the instrument or spacecraft RSS2.0 http://winds.jpl.nasa.gov/missions/quikscat/
description A short description of the feed RSS2.0 The Satellite Communications Facility at the Johns Hopkins University / Applied Physics Laboratory regularly receives and the Ocean Remote Sensing Group records and processes imagery from the Advanced High Resolution Radiometer (AVHRR) on the NOAA polar-orbiting satellites.
datacasting: channelUID String which uniquely identifies the datastream and is used in forming the datastore directory name. datacasting  
 
Optional Channel Elements
Element Description Namespace Example
managingEditor The email address of the person responsible for the feed. RSS2.0 BigDog@jpl.nasa.gov
webMaster Email address of the webmaster RSS2.0 BigDogWebmaster@jpl.nasa.gov
lastBuildDate The last time the content changed. We recommend that this element is included for performance reasons. RSS2.0 <lastBuildDate> Wed, Jul 12, 15:55:00 PDT </lastBuildDate>
generator A string indicating the program used to generate the channel RSS2.0 <generator> Datacasting Server 0.0.1a </generator>
docs A URL pointing to a description of the Datacasting RSS feed specification RSS2.0 <docs> http://datacasting.jpl.nasa.gov/ datacasting_mod </docs>
ttl Time to Live - the number of minutes the channel can be cached before being reloaded from the source RSS2.0 <ttl>60</ttl>
skipHours Hours of the day when the feed will not be published RSS2.0 <skipHours> 23,0,1,2,3 </skipHours>
skipDays Days of the week then the feed will not be published RSS2.0 <skipDays>SAT, SUN</skipDays>
datacasting: format The description of the data file format in ESML. Also define an attribute: URL which points to a ESML file served off the provider's site which we cache on download of the product. May specify an isPermaLink attribute (see guid in RSS2.0) datacasting ESML to indicate HDF-SFS
(NOTE: ESML support to be added ibeginning April 2008)
datacasting: dataSource A string indicating the name of the instrument/platform/etc. with which the data was collected and processed datacasting <datacasting:dataSource> AVHRR </datacasting:dataSource>
datacasting: customEltDef This element will define any custom metadata items. The element will have required "name" and "type" and optional "displayName" and "units" attributes which will specify the kind of metadata.

Valid types are: string, integer, float, boolean, date, point, envelope. Boolean values can be either "true" or "false". Date accepts another optional attribute, "format", that specifies how values will be parsed, default format is UTC. See Sun Java docs for SimpleDateFormat.		 datacasting <datacasting:customEltDef name="quadrantId" type="integer" />

<datacasting:customEltDef name="rainDepth" type="float" units="cm" />

<datacasting:customEltDef name="stormDescription" type="string" />

<datacasting:customEltDef type="date" name="hurricaneDate" format="yyyy-MM-dd'T'HH:mm:ss.SSSZ" />

<datacasting:customEltDef type="boolean" name="overLand" displayName="Hurricane is Over Land" />

<datacasting:customEltDef type="point" name="hurricaneCenter" displayName="Hurricane Center" />

<datacasting:customEltDef type="envelope" name="regionOfInterest" displayName="Region of Interest" />
 
Candidate Channel Elements
datacasting: dataAnalyst The email address of an engineer who understands the data and would be cabable of understanding and adding custom elements to the feed. datacasting BigDog@jpl.nasa.gov
 
Required Item Elements
Element Description Namespace Example
title Title of the item RSS2.0 <title>Day 1, 2005 AVHRR Sea Surface Temperature</title>
link Link to an HTML document for the item RSS2.0 <link>http://podaac.jpl.nasa.gov/ </link>
description Short description of the item RSS2.0 <description>4km Sea Surface Temperatures</description>
enclosure Describes the data object attached to this item RSS2.0 <enclosure length=13601501 url="ftp://podaac.jpl.nasa.gov/ daily/ascending/4km/2005/sst/ 2005001.s04d4pfrt-sst.hdf" type="x-data/hdf-eos"\>
datacasting: fileName A filename which the Feed Reader will use when downloading and saving the enclosure. Some enclosure URLs may not imply a simple filename, so this is the place to specify it. This is required if you have an enclosure. datacasting <datacasting:productName> foo-bar-20060905-blah.nc </datacasting:productName>
pubDate Date that this item was published RSS2.0 <pubDate>Fri, Mar 17, 2006 3:58 UTC</pubDate>
 
Optional Item Elements
Element Description Namespace Example
source RSS channel from which this item came RSS2.0 <source>datacasting.jpl.nasa.gov/ example-feed.xml</source>
guid A string which uniquely identifies this item RSS2.0 <guid>2005001.s04d4pfrt-sst.hdf</guid>
datacasting: acquisitionStartDate Date of the data item collection start at the instrument datacasting <datacasting:acquisitionStartDate>
Tue, 26 Jun 2007 13:47:00 GMT
</datacasting:acquisitionStartDate>
datacasting: acquitisionEndDate Date of the data item collection end at the instrument datacasting  <datacasting:acquisitionEndDate>
Tue, 26 Jun 2007 13:52:00 GMT
</datacasting:acquisitionEndDate>
datacasting: acquitisionDuration The duration of data collection (for observations where duration is short or unimportant, this can be omitted) in HH:MM:SS.sss datacasting <datacasting:acquisitionDuration>
00:05:00.00
</datacasting:acquisitionDuration>
georss: where Describes the location of the data product georss <georss:where>
<gml:Envelope>
<gml:lowerCorner>31.000000 16.000000</gml:lowerCorner>
<gml:upperCorner>56.000000 72.000000</gml:upperCorner>
</gml:Envelope>
</georss:where>
datacasting: customElement Any tags assocaiated with a previously declared datacasting:customEltDef above. This element shall include "name" and "value" attributes elements specifying a value instance of custom metadata with the same name for this item.

In the case of customElements that contain georss markup (point and envelope types), the value attribute is unused and the value appears between the tags. (see example at right)

Instances of customElement without a customEltDef cannot be processed.		 datacasting <datacasting:customElement name="quadrantId" value="3"/>

<datacasting:customElement name="rainDepth" value="8.12"/>

<datacasting:customElement name="stormDescription" value="4 miles off the coast of Florida"/>

<datacasting:customElement name="hurricaneData" value="2009-09-12T12:34:56.789-0800"/>

<datacasting:customElement name="overLand" value="true"/>

<datacasting:customElement name="hurricaneCenter">
<georss:where>
<gml:point>
<gml:pos>35.4 -120.75</gml:pos>
</gml:point>
</georss:where>
</datacasting:customElement>

<datacasting:customElement name="regionOfInterest">
<georss:where>
<gml:Envelope>
<gml:lowerCorner>31.000000 16.000000</gml:lowerCorner>
<gml:upperCorner>56.000000 72.000000</gml:upperCorner>
</gml:Envelope> </georss:where>
</datacasting:customElement>
 

 
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