Reference implementations

[Tom McGlynn (NASA/GSFC Code 660.1)]

If you feel that data models are not subject to the requirement of two 
reference implementations, that's fine but then this discussion is moot 
regardless.  If you think they are then you are quibbling about my 
choice of words. Feel free to substitute whichever you like for 'protocol'.

     Regards,
     Tom

Matthew Graham wrote:
> But a data model is not a protocol.
>
> -- Matthew
>
> On May 10, 2016, at 4:37 PM, Tom McGlynn (NASA/GSFC Code 660.1) wrote:
>
>> This kind of using the fact that you have written a definition of the model counting as an implementation of the model sounds awfully incestuous. I have always read the requirement as having two different groups using the protocol in some service, ideally one that supports doing astronomy.
>>
>>     Tom McGlynn
>>
>> Matthew Graham wrote:
>>> So once we have a mapping standard with reference implementations any DM model specified in VO-DML could automatically have a reference implementation (according to these criteria) which would make life easier. Time to get that mapping spec out :)
>>>
>>> -- Matthew
>>>
>>>
>>>
>>> On May 10, 2016, at 4:00 PM, Laurino, Omar wrote:
>>>
>>>> Hi,
>>>>
>>>> I agree with Gerard that items 1) and 2) look like the same, unless one brings in a standard for instance serializations. Since we can have standardized mapping strategies (as different recommendations) that map instances of valid VODML/XML models and their standard serializations, I don't think a valid serialization of an instance should be required for data models: this should be guaranteed by the mapping standard(s) and their reference implementations.
>>>>
>>>> As for the ModelImport requirement, it makes sense for "low level" models but not for "high level" ones, plus there is no way to guarantee that all types defined by a model are extendable/usable by other models. It gets too complicated.
>>>>
>>>> I would suggest we include the "model import" evidence as a "soft requirement", to be evaluated on a case-by-case basis depending on the use cases of the model. For STC, it makes a lot of sense to require this additional proof of interoperability, because the model is intended to be a building block for other models.
>>>>
>>>> Or, we might be to *require* that at least one reference implementation is a mission/archive/service-specific model that extends the standard one. So, if we had a model for Sources/Catalogs, at least one reference implementation should be a mission/archive/system-specific model that proofs the model can be meaningfully extended by actual specializations. Other than properly validating as VODML/XML, this model should be evaluated for its domain-specific content, and that's probably not something you can automate. This should also be a good way to involve implementors from the community, so it's probably my preferred one.
>>>>
>>>> Omar.
>>>>
>>>>
>>>> On Tue, May 10, 2016 at 9:38 AM, Gerard Lemson <gerard.lemson at gmail.com <mailto:gerard.lemson at gmail.com>> wrote:
>>>>
>>>>     Hi
>>>>     What is meant by item 2, "An XML serialization of the DM".
>>>>     The standard representation (serialization?) of a VO-DML data
>>>>     model is VO-DML/XML, i.e. XML. And that is the representation
>>>>     that can be validated (step 1?) using automated means, for
>>>>     example using XSLT scripts in the vo-dml/xslt folder on volute at gavo.
>>>>     If 2) is meant to imply an XML serialization of an *instance* of
>>>>     the model, that we can only do once we have a standard XML
>>>>     representation of instances of models. That does not yet exist.
>>>>     The original VO-URP framework does contain an automated XML
>>>>     Schema generator for its version of VO-DML, that has not yet been
>>>>     ported to VO-DML.
>>>>     And of course the mapping document describes how one can describe
>>>>     instances serialized in VOTable, but that is a different standard.
>>>>
>>>>     For what it's worthy, I think that an "implementation of VO-DML"
>>>>     is a data model expressed using that language (in VO-DML/XML to
>>>>     be precise) and validated using software. The latter enforces
>>>>     that the language should allow automated validtion.
>>>>     I think interoperable implementations of VO-DML are two or more
>>>>     valid models that are linked by "modelimport" relationships.
>>>>     I.e.one model "imports" the other(s) and uses types from the
>>>>     other as roles or super types in the definition of its own types.
>>>>     This is supported by the VODMLID/VODMLREF meachanism of the language.
>>>>
>>>>     Cheers
>>>>     Gerard
>>>>
>>>>
>>>>     On Tue, May 10, 2016 at 9:04 AM, Matthew Graham
>>>>     <mjg at cd3.caltech.edu <mailto:mjg at cd3.caltech.edu>> wrote:
>>>>
>>>>         Hi,
>>>>
>>>>         We're trying to define specifically what would satisfy the
>>>>         reference implementation requirement for an IVOA Spec in the
>>>>         context of a data model. The proposal is that:
>>>>
>>>>         (1) If the DM has been described using VO-DML it can be
>>>>         validated as valid VO-DML
>>>>
>>>>         (2) An XML serialization of the DM can be validated
>>>>
>>>>         so therefore is the combination of the two sufficient to
>>>>         demonstrate the validity and potential interoperability of
>>>>         the data model (which is the purpose of the reference
>>>>         implementations).
>>>>
>>>>                 Cheers,
>>>>
>>>>                 Matthew
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> -- 
>>>> Omar Laurino
>>>> Smithsonian Astrophysical Observatory
>>>> Harvard-Smithsonian Center for Astrophysics
>>>> 100 Acorn Park Dr. R-377 MS-81
>>>> 02140 Cambridge, MA
>>>> (617) 495-7227