- From: Felix Sasaki <fsasaki@w3.org>
- Date: Sat, 24 Jan 2009 17:31:06 +0900
- To: Pierre-Antoine Champin <pchampin@liris.cnrs.fr>
- CC: public-media-annotation@w3.org
Pierre-Antoine Champin さんは書きました: > Hi, > > for action 78, I had to write a wiki page about some concerns I raised > during the last telecon about interoperability between mapped > properties. Since this is supposed to be matter for discussion rather > than a formal document, I think it is best to send it as a mail. > > > What triggered my concern was the mapping for Media RSS, between > ''dc:creator'' and ''dcterms:creator''. Just as a reminder, the Dublin > Core vocabulary has two versions: the legacy "elements" (usually > prefixed with ''dc'') and the "terms" (usually prefixed with > ''dcterms''). Each term is more specific than its corresponding element, > as its values are more constrained. For example, ''dc:creator'' can have > any type of value (including a plain string), while 'dcterms:creator'' > must have a URI, which must denote an instance of ''dcterms:Agent''. > If we decide to specify the ontology only as prose > Let us consider the example of ''dc:creator'' with a sample of mappings: > > * for XMP, its value is a sequence of strings, each string being the > name of an author. > > * for Media RDF, its value is either > - a plain string, > - an instance of ''foaf:Agent'' with at least a ''foaf:name'', or > - an instance of ''vcard'' with at least a ''fn''. > Since they are using ''dcterms'', it must also be inferred to be a > ''dcterms:Agent'' (which contradicts the use of a plain string...). It > may represent only one ("the primary") creator. > > * for ID3, the value of TOPE is a string, where names are separated by "/". > > > My point here is that, beyond the "high level" semantic links identified > by the mapping table, there are some "low level" discrepancies that are > both semantic (e.g. representing one or several creators) and syntactic > (slash-separated string or structured sequence). > > Leaving these issues to the implementation will inevitably lead to major > differences and a lack of interoperability. We could specify down to the > syntactical level the mapping for each property in each format, but what > about other formats ? > > I think a better way to limit the variability in implementations by > specifying precisely, for each property of our ontology, the expected > "low level" features of its value (and not only its "high level" > meaning) so that implementors know what they can keep from the original > metadata, and what they need to adapt (i.e. split ID3's TOPE field into > multiple values). > > This has to be done at least at the API level. But I guess this could > also be done to some extent at the ontology level (I do believe that > those "low level" features are *not only* syntactic), but that raises > again the problem of formally specifying the ontology or not. > > But the less specific we are in describing the ontology, the more > precise we will have to be in describing the API, in order to avoid "low > level" semantic discrepancies. > I agree very much with your analysis, Pierre-Antoine. +1 to have a very low wheight ontology and to be more precise in the API description. Also I am hoping very much that people will volunteer to actually test the mappings in toy implementations, no matter if relying on a complex ontology or a detailed API. No matter which way we go, let's test them now. Felix > regards > > Pierre-Antoine > > > >
Received on Saturday, 24 January 2009 08:31:52 UTC