Re: Observation Dataset Conventions


I think it would be great if you could work with Joe Sirott's group to
create an explicit Convention that would be consistent with the use of
something like the Dapper doubly nested sequences for collections of
profiles and time series.  I would prefer that you inquire if they are

If this is only a few days work, I would put it at a fairly high
priority, especially if there's a chance we could have be working on a
draft Convention before the GO-ESSP meeting, as a concrete example of
greater interoperability that could be achieved by extending the CF
conventions to handle this kind of data.

I'm also Cc:ing Steve Hankin to let him know about the possibility of
you and Joe Sirott's group working together on this.

Also, our IOOS DMAC team considers this a high priority, and is making
a recommendation about it to the DMAC Steering Team next week.  I'd
give you a URL, but it's currently on a restricted access Wiki.  I'll
send the text of the recommendation in the next email ...


John Caron wrote:
> The UnidataObsConvention are a recommendation for how to write observation 
> data into netcdf-3 files. Dappper is a method of serving this kind of data 
> through OpenDAP. So the closest analogue would be to make the TDS serve 
> (through opendap) UnidataObsConvention files using the same structures as 
> Dapper. Currently if you throw those files at the TDS openddap server, you 
> would see the linked lists, which makes performance suck, because each read 
> of an obs becomes a round trip to the server.
> I was thinking of solving this at the "Point Obs" datatype API, but the idea 
> of using the dapper doubly nested sequences seems like a viable alternative.  
> There are probably a few subtle issues concerning performance and 
> scalability, however, and the fastest way to discover them is probably to 
> just implement it and see.
> The docs you point to implicitly describe dapper "Conventions". Probably with 
> some interaction between us and Joe Sirott's group, we could create an 
> explicit Convention. Do you want to inquire if they are interested, or should 
> I, or ? Its probably only a few days work. How high a priority is this from 
> your POV?
> Russ Rew wrote:
> > Ethan,
> > 
> > 
> >>I don't know enough about the Dapper convention to give a really good 
> >>answer to this. Is there a link from the Dapper page that goes into 
> >>detail on their convention? I did see where it mentions the GDS but 
> >>still didn't find any details on the convention. One thing is that 
> >>Dapper uses nested structures a fair amount while the Unidata obs 
> >>convention doesn't really go into that much. Perhaps because their 
> >>backends are database driven and we're nc3 based. We also haven't dealt 
> >>with some data types that might require more sequence type stuff.
> > 
> > 
> > My understanding is that Dapper serves a doubly-nested sequences, such as:
> > 
> > Sequence{ lon,
> >       lat;
> >       depth;
> >       Sequence{ temperature, 
> >                     time} time_series;
> >         } mooring_collection;
> > 
> > This is the closest I've seen to describing the Dapper OPeNDAP output
> > conventions:
> > 
> >
> > 
> > For input, it aggregates netCDF data that follows several conventions:
> > 
> >     * ARGO GDAC netCDF
> >     * ARGO NODC netCDF
> >     * EPIC netCDF
> >     * Opendap sequence data (must follow Dapper metadata conventions).
> > 
> >
> > 
> > 
> >>As far as agreeing on consistent conventions. Seems like it would be a 
> >>good idea, probably take a bit of work on both sides to understand both 
> >>data models. John has talked to Joe Sirott about Dapper more than I have 
> >>(and probably looked at Dapper more closely as well) so he may have more 
> >>details he can provide.
> > 
> > 
> > OK, thanks for the information.  I'm just trying to learn enough about
> > this to be able to defend a recommendation we are making to the IOOS
> > DMAC Steering Team, to use Dapper in a pilot project.
> > 
> > --Russ

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