[Esip-discovery] Datacasting, collection casting -- these should be harmonized

Mon Jan 28 10:57:42 EST 2013

There's a NASA RFC out for a RSS feed to publish metadata about satellite
image granules as they come in. The key content seems to be an
rss2:enclosure element with a link to a specific granule file (a kind of
dataset). Metadata beyond the standard RSS elements is completely soft
typed, therefore only interoperable within the confines of some community
profile about the datacasting:customEltDef's.

There's an ESIP RFC for an ATOM feed to publish metadata about collections.
The intention, based on the RFC, appears to be to enable software clients to
parse the feed content (atom:link elements) and set up interfaces for users
to access subsets of a dataset described by the feed. The RFC adopts
conventions for specifying geographic and temporal coverage (important). The
interesting thing (IMHO) about the ESIP proposal is the idea of include
links with opensearch descriptions for how to access subsets of the dataset,
e.g. using openDAP type requests, or OGC filter for WFS or CSW type
requests. The fact that there is an interface that allows URL-based subset
requests seems to be what makes something a collection.  

Its unclear to me why the community would need two such similar
specifications, other than to codify existing implementations. If the NASA
Datacasting RFC is just describing an existing RSS implementation, perhaps
it should be named something more like 'NASA satellite data RSS
conventions'?  If the NASA Datacasting proposal is meant to be forward
looking, perhaps it should utilize some of the ISO metadata conventions that
are being adopted by NASA
(http://earthdata.nasa.gov/wiki/main/index.php/ISO_19115_Home), consider
using ATOM instead of RSS, use registered MIME types?

steve

> -----Original Message-----
> From: esip-discovery-bounces at lists.esipfed.org [mailto:esip-discovery-
> bounces at lists.esipfed.org] On Behalf Of Lynnes, Christopher S. (GSFC-6102)
> Sent: Monday, January 28, 2013 5:39 AM
> To: Ruth Duerr
> Cc: Bingham, Andrew W; datacasting at list.jpl.nasa.gov; esip-
> discovery at lists.esipfed.org
> Subject: Re: [Esip-discovery] RFC ready to go?
> 
> Alright-y, I have (hopefully) disambiguated datacasting from collection
casting in
> the document, while leaving in a reference to the sibling DatacastingRSS.
> 
> On Jan 28, 2013, at 1:29 AM, Ruth Duerr <rduerratnsidc at gmail.com> wrote:
> 
> > Hi Chris,
> >
> > I finally did my homework from the ESIP meeting.  I seriously think that
there
> are enough differences between the Discovery cluster's conventions for
> OpenSearch/Collection Casting and Andy's Datacasting, that the two things
> should be kept quite separate.  So I disagree with Andy's suggestions
below.  I've
> put a number of comments in the google doc but was unable to actually edit
it.
> >
> > In any case, DataCasting has its own RFC and I think that is
appropriate.
> >
> > As for what to call the document, I tend to agree with Andy that there
are a lot
> of technologies that legitimately fall under the heading of "discovery".
The ESIP
> Discovery cluster has only worked on OpenSearch/Collection Casting, so
> perhaps the title should reflect that.
> >
> > Ruth
> >
> > On Jan 25, 2013, at 4:34 PM, "Bingham, Andrew W (3880)"
> <andrew.w.bingham at jpl.nasa.gov> wrote:
> >
> >> Chris et al.,
> >>
> >>  My apologies for not responding earlier - I'm not on the cluster email
list and
> received your recent email only via Nga.
> >>
> >> Below are my  comments to your RFC.
> >>
> >> Andy
> >>
> >>
> >>
> >> 1.  Replace Section 7.1.2 with an introduction to Datacasting.  Below
is my
> proposed text - which is intended to clear-up confusion with the
peer-reviewed
> literature.
> >>
> >> 7.1.2 Introduction to Datacasting
> >> Datacasting is  a publish-subscribe method where a data provider
publishes
> the availability of new data granules (data files) via an XML feed and a
data
> consumer subscribes to the feed to learn about recently available data
(Bingham
> et al., 2009).   The Datacasting Project
(http://datacasting.jpl.nasa.gov), which
> was funded under the NASA ACCESS Program (2005 and 2009), developed an
> RSS-based specification for the XML feeds, which is termed DatacastingRSS.
A
> NASA RFC for DatacastingRSS is currently under consideration
>
(https://earthdata.nasa.gov/wiki/main/images/a/a6/Datacasting-Standard-RFC-
> 20121108.pdf).  In this specification, data files related to a data set
are cast out
> in a single feed.  Linkages to the data set information is provided via
elements
> embedded in the channel tag;  information related to the data file
(spatial and
> temporal extent, link to the data file, browse representation etc.) are
provided
> via elements embedded in the item tag.  The DatacastingRSS specification
also
> allows for the definition and addition of "custom elements" that allows
data
> providers to add their own elements to the item tag. The default and
custom
> elements within the item tags, enables a Datacasting Feed Reader to filter
lists
> of items so data consumers can discover and utilize specific files.
> >>
> >> In this RFC, we have slightly modified the definition of the term
"Datacasting"
> - we consider Datacasting as a publish-subscribe method, but we extend its
use
> for announcing the availability of data sets, as well as data files. The
Atom
> specification proposed in this RFC therefore unifies the terminology for
> publishing data sets and data files.  However, the specification lacks the
concept
> of "custom elements" that exists under DatacastingRSS and therefore limits
the
> number of facets by which a user can discover files.
> >>
> >> References
> >> Bingham A.W, S. McCleese, T. Stough, R. G. Deen, K. Hussey and N.
Toole,
> 2009, Earth Science Datacasting: Informed Pull and Information
Integration,
> IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 47, NO. 10,
> OCTOBER 2009.
> http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5191107.
> >>
> >>
> >> 2.  The title "ESIP Discovery Conventions" is  too broad - I'd like to
think that
> DatacastingRSS is an ESIP Discovery Convention, but obviously does not fit
into
> your RFC!
> >> A more accurate title would be : Atom-based Discovery Conventions.
> >>
> >> 3.  Include tables illustrating the Atom specification for OpenSearch
and
> Datacasting respectively.  See the DatacastingRSS RFC for an example.
> >>
> >>
> >> ---
> >> Andrew W Bingham
> >> andrew.bingham at jpl.nasa.gov
> >>
> >> 818-354-1768 (office)
> >> 818-687-0626 (mobile)
> >>
> >>
> >> On 1/24/13 5:21 PM, "Quach, Nga T (388A)" <Nga.T.Chung at jpl.nasa.gov>
> wrote:
> >>
> >>>
> >>>
> >>>
> >>> Begin forwarded message:
> >>>
> >>>> From: "Lynnes, Christopher S. (GSFC-6102)"
> <christopher.s.lynnes at nasa.gov>
> >>>> Date: January 24, 2013, 12:31:54 PM PST
> >>>> To: "<esip-discovery at lists.esipfed.org>" <esip-
> discovery at lists.esipfed.org>
> >>>> Subject: [Esip-discovery] RFC ready to go?
> >>>>
> >>>> In terms of modifications to the ESIP Discovery RFC, it looks like we
have
> reached a stabilization point.  I am now going to import it into MS Word
next
> week, reformat a little and add table of contents.  So if there is
anything that still
> needs changing, speak (or write) now or forever etc etc etc.
> >>>>
> >>>>
> https://docs.google.com/document/d/1ymt5vsP2jw2YMVnc2B8uEI0BKTHcT4jS
> NVQzruLIFPA/edit
> >>>> --
> >>>> Dr. Christopher Lynnes     NASA/GSFC, Code 610.2    phone:
301-614-5185
> >>>> "Perfection is achieved, not when there is nothing left to add, but
when
> there is nothing left to take away" -- A. de Saint-Exupery
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> Esip-discovery mailing list
> >>>> Esip-discovery at lists.esipfed.org
> >>>> http://www.lists.esipfed.org/mailman/listinfo/esip-discovery
> >> _______________________________________________
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> >
> > _______________________________________________
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> 
> --
> Dr. Christopher Lynnes, NASA/GSFC, ph: 301-614-5185
> 
> 
> 
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