Difference between revisions of "Discovery Cast Atom Response Format v1.1"
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Revision as of 15:52, March 8, 2011
Notice
- This specification is based on DCP-1: ESIP Discovery Cast Atom Response Format v1.1
- This is currently a working draft document.
- See other versions.
- See Discussion Page for discussion of this.
Introduction
At the NASA Earth Science Data System Working Group meeting in New Orleans on October 21, 2010, a proposal was made to expand the scope of Federated search to cover Discovery more generally, thus bringing into the fold datacasting and servicecasting. Therefore a common Atom response format is needed that extends the Atom Syndication Format (RFC 4287) with extensions specific for Earth science data usage.
Scope
The Response Format is a common format used by OpenSearch, datacasting and servicecasting. However, note that some attributes (e.g., the Geo elements) may be less relevant for certain types of casts.
Namespace
- discovery: "http://esipfed.org/ns/discovery/1.1/"
Geo extensions
Adopted from the OpenSearch Geo extension and GeoRSS-Simple specifications. Use the "georss" namespace for defining box, circle, and polygon regions for each entry.
box (required support)
A bounding box with coordinates (west, south, east, north).
Example:
<georss:box>-180.0 -90.0 180.0 90.0</georss:box>
circle (optional)
A shape containing three coordinates (centerpoint latitude, centerpoint longitude, circle radius), where the lat/lon are in WGS84 format, and radius is in meter units.
Example of radius around a lat/lon point:
<georss:circle>34.0 -118.0 10000</georss:circle>
polygon (optional)
A list of lat-lon pairs in WGS84 format. space-delimited.
Example of radius around a lat/lon point:
<georss:polygon>45.256 -110.45 46.46 -109.48 43.84 -109.86 45.256 -110.45</georss:polygon>
Time extensions
Similar to the OpenSearch Time extension. Use the "time" namespace for defining time start and end for each entry. vallues for times must be in ISO 8601 string format.
Example:
<time:start>2005-01-01T00:00:00Z</time:start> <time:end>2005-01-01T03:00:00Z</time:end>
rel links
rel
Link type | Description |
---|---|
http://esipfed.org/ns/discovery/1.1/data# | Default data link. Data Casting Granules. OpenSearch Granules response. |
http://esipfed.org/ns/discovery/1.1/browse# | Appropriate for smaller browse images. See following for alternate browse links. |
http://esipfed.org/ns/discovery/1.1/documentation# | Default documentation. See following for alternate documentation links. |
http://esipfed.org/ns/discovery/1.1/metadata# | Data, collection, and service metadata. |
http://esipfed.org/ns/discovery/1.1/collection# | Data Casting Collection. Not for OpenSearch Collection response which uses OSDD instead. |
http://esipfed.org/ns/discovery/1.1/service# | Service Casting. |
http://esipfed.org/ns/discovery/1.1/event# | Natural phenomenon. |
http://esipfed.org/ns/discovery/1.1/feed# | Feed of various feeds. |
types
The rel links shall have an expected return type. Currently, there are no constraints on allowed types. Though a mime-type is highly recommended.
Example
<link href="http://host.com/my/file.nc" length="64959344" rel="http://esipfed.org/ns/discovery/1.1/data#" title="Granule File" type="application/x-netcdf" />
Pagination Support
Should we follow something like the OpenSearch convention for pagination? Pagination stats would be under the "opensearch" namespace. rel links to other pages contain precomputed links to the other paged feeds.
Example
<feed> ... <link href="http://host/to/this/feed" rel="self" /> <link href="http://host/to/first/page/feed" rel="first" /> <link href="http://host/to/next/page/feed" rel="next" /> <link href="http://host/to/last/page/feed" rel="last" /> <opensearch:totalResults>1000000</opensearch:totalResults> <opensearch:startIndex>0</opensearch:startIndex> <opensearch:itemsPerPage>10</opensearch:itemsPerPage> ... </feed>
Custom tag extensions
Domain-specific tags can be added with namespace at the top-level of <entry> tags.
Example
<entry> ... <gesdisc:dayNightFlag>day</gesdisc:dayNightFlag> ... </entry>
Example ESIP Discovery Atom response
An example of an Atom discovery response feed:
<?xml version="1.0" encoding="UTF-8"?> <feed xmlns="http://www.w3.org/2005/Atom" xmlns:opensearch="http://a9.com/-/spec/opensearch/1.1/" xmlns:georss="http://www.georss.org/georss"> <title>Granules</title> <updated>2010-12-13T18:30:02Z</updated> <author> <name>A NASA Center</name> </author> <id>urn:uuid:00000000-0000-0000-0000000000</id> <opensearch:totalResults>100000</opensearch:totalResults> <opensearch:startIndex>0</opensearch:startIndex> <opensearch:itemsPerPage>10</opensearch:itemsPerPage> <entry> <title>regrid-modis.aqua-avg.1hr.p5deg-v1.0-2005.01.01.blk1.nc</title> <link href="http://host.com/my/file.nc" length="64959344" title="Granule File" type="application/x-netcdf" /> <link href="http://host.com/my/file.nc" length="64959344" rel="http://esipfed.org/ns/discovery/1.1/data#" title="Granule File" type="application/x-netcdf" /> <geo:box>-180.0 -90.0 180.0 90.0</geo:box> <time:start>2005-01-01T00:00:00Z</time:start> <time:end>2005-01-01T03:00:00Z</time:end> <updated>2008-12-16T15:00:26Z</updated> </entry> </feed>
References
- OpenSearch
- OpenSearch Geo extension
- OpenSearch Time extension
- OpenSearch convention for pagination
- GeoRSS-Simple
- OGC OpenSearch GeoSpatial and Temporal Extensions (link needed)