Re: Intrinsic vs extrinsic metadata (my action #54)

Hi Andrea,

Thanks again for your comments and for being part of this discussion!
Please, find some more comments below:

>> 2. From the diagram it is not clear if some metadata elements are
> specific to data, datasets or their distributions, or, rather, they can be
> used for all of them. E.g., "access metadata" are just for distributions or
> also for data/sets?
> >
> > The initial idea was to identify metadata to describe datasets. I
> included access metadata is part of the classification, but I'm not sure if
> this type of metadata should be used to describe datasets or distributions.
> Moreover, it is not clear for me what types of metadata should be used to
> describe the distributions. For example, should we use the same ones that
> we use to describe datasets?
>
> IMHO, this depends on how the different entities are defined. E.g.,
> supposing that the notions of dataset and distribution correspond to
> the ones defined in DCAT, access metadata concern distributions - a
> dataset is an abstract entity, you can access just its representations
> - or manifestations, using the FRBR terminology.
>

I agree with you Andrea! Dataset is an abstract entity and it makes more
sense that distributions have access metadata instead of the dataset
itself. However, I think that we can keep the metadata hierarchy proposed
in the diagram of [1]. Then, later on we need to identify what type of
metadata concerns datasets or distributions.


> >> 3. I wonder whether structural metadata are meant to describe only the
> structure (database schema) or also the content (database instances)?
> Actually, in VoID structural metadata are doing both.
> >
> > Structural metadata should describe the data itself. They should provide
> an interpretation for the dataset content (i.e. the data). It can be seen
> as the vocabulary (ontology) that describes the data. I think this idea is
> different from the structural metadata proposed by VOID. If you have a RDF
> distribution for a given dataset, maybe you can have a VOID description for
> this specific distribution.
>
> I see the point. So, the description is only intensional (i.e., about
> the characteristics of the entities in the dataset), or also
> extensional (e.g, how many entities are in the dataset, and which are
> such entities)?
>

Yes, in this case is only intensional. Information about the number of
triples is specific for RDF distributions, and it should be part of the
metadata that describes the distribution. Does it make sense for you?


> >> 4. The diagram does not model the fact that metadata are, in turn,
> data. As such, metadata records may be available in different formats
> (metadata distributions) and they can be described by other metadata (this
> scheme is, in theory, recursive). A real world example is given by INSPIRE
> [1], where we have "metadata on metadata", providing information concerning
> the provenance of a metadata record (responsible, language,
> creation/publication/modification dates).
> >
> > Yes, this is a good observation! I agree that metadata itself may have
> some properties (metadata) . Maybe, we can consider that these properties
> will be associated to the class metadata and will be inherited by the
> sublasses. Does it make sense for you?
>
> I was thinking that, in order to model this, it might be enough to
> make metadata as a subclass of entity "data". This would also model:
> - the "recursive" nature of metadata (i.e., in theory, you may have
> metadata on metadata, which in turn can be described by other metadata
> and so on);
> - the fact that, as data, also metadata have distributions.
>
>
I was trying to represent this in the diagram, but it is not easy. I
considered metadata as a subclass of data, so both data and metadata may
have different distributions. However, I consider that the dataset itself
is decribed by metadata not the data. In this case, we need another
association to represent that metadata is also described by metadata. I
attached the pdf version of the diagram together with the ppt. Please, let
me know what do you think and fell free to make modifications.

Thanks again!
Bernadette



> Cheers,
>
> Andrea
>


[1] http://lists.w3.org/Archives/Public/public-dwbp-wg/2014Jul/0006.html


-- 
Bernadette Farias Lóscio
Centro de Informática
Universidade Federal de Pernambuco - UFPE, Brazil
----------------------------------------------------------------------------