Hi Doug, all,
I've been working on a Java API, inspired by the Climate Science
Modelling Language, whose data model is very similar to that of the CDM
(and one day they might be completely harmonized). This is intended to
be a "thin skin" API that provides a common, "GIS-friendly" interface to
datasets in various forms. We use it to access data in various forms
(including NetCDF, through nj4). The primary use case is to enable
simple visualization and intercomparison of models and observations in
GIS-like applications. It is evolving from a refactoring of our ncWMS
software.
The code is not quite ready for sharing yet, but please reply off-list
if you're interested in using, or contributing to, the library.
(Apologies for using this list to make a plug, but it seemed relevant to
the conversation...)
Cheers, Jon
-----Original Message-----
From: netcdf-java-bounces@xxxxxxxxxxxxxxxx
[mailto:netcdf-java-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Doug Lindholm
Sent: 28 March 2010 18:59
To: John Caron
Cc: netcdf-java@xxxxxxxxxxxxxxxx
Subject: Re: [netcdf-java] Common Data Model plans
Hi John,
While presenting our Time Series Data Server poster
(http://sourceforge.net/projects/tsds/files/TSDS_poster_nobg.pdf/downloa
d)
at AGU, for example, I talked with some people who live in a CDF centric
environment. They have their tools that are likewise tightly coupled to
the CDF APIs. It is not realistic for them to refactor their system and
retool their clients to use the NetCDF libraries, but it may be
reasonable for them to abstract out a CDM interface and break the
coupling between "client" code and "server" code. Once that happens, any
code that writes to the CDM interface can interoperate.
I agree that providing the ideal CDM API is a grand idea and bound to be
fraught with pesky reality. So, I guess my question is, is such an API
part of the vision for the CDM? I take it the answer is that it is
desirable but not immediately practical, or funded.
Thanks,
Doug
On 3/27/10 12:03 PM, John Caron wrote:
> Hi Doug:
>
> While there are some simple UML descriptions of the CDM, the real
> work and thought is in the netcdf-Java library and API. It evolves
> from the ground up, as we deal with more datasets and data types.
>
> In an ideal world, we probably would develop an interface that
> corresponds to a "pure" CDM description. In the real world, theres
> not enough resources or motivation to do so. Also, its still evolves,
> esp at the feature type APIs, and i dont think its time yet to cast
> that in stone.
>
> Can you describe some use-case in some detail? Why would a group
> "never adopt NetCDF-Java" ? What is the issue there that could be
> solved by a lightweight API ?
>
> John
>
>
>
> Doug Lindholm wrote:
>> I still intend to focus on Java, but I want to be able to plug in
>> a light-weight alternative to NetCDF-Java. I have a system with a
>> data model implementation that is consistent with the CDM. Instead
>> of writing an IOSP or subclassing NetcdfFile and taking on all of
>> NetCDF's dependencies, I'd like to have a Java Interface that my
>> data model could implement. All "client" code would then write to
>> that interface. NetCDF and other implementations of that same
>> interface would then be usable by that same client.
>>
>> I work with groups that will never adopt NetCDF-Java but they
>> might implement a simple set of Java Interfaces with their data
>> model. This would lower a lot of barriers to interoperability. Is
>> the CDM moving in this direction or is the plan to expose all other
>> data via the NetCDF-Java API?
>>
>> Thanks, Doug
>>
>> On 3/26/10 2:15 PM, Richard Signell wrote:
>>> Doug,
>>>
>>>> What is the state of the Common Data Model
>>>> (http://www.unidata.ucar.edu/software/netcdf-java/CDM/)? Is
>>>> there a complete definition of the model. The UML on that page
>>>> communicates the idea well, but I'd like to see an interface
>>>> that I could program to. Right now, I am uncomfortably tightly
>>>> coupled to the NetCDF Java implementation.
>>>
>>> What other language are you planning to be coupled to?
>>>
>>> Just thought others in the community might be curious besides
>>> me.
>>>
>>> -Rich
>>>
>>
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