Schema.org Alignment Task Group - 2012-04-05 telecon - report
Agenda: http://wiki.dublincore.org/index.php/Schema.org_Alignment/Telecon_20120405
This report: http://wiki.dublincore.org/index.php/Schema.org_Alignment/Telecon_20120405_Report
Present: Tom (chair), Karen, Gordon, Antoine, Bernard, Kai (IRC)
Tom: We have:
* wiki pages with the information we need for comparing terms to be mapped (e.g., [1])
* pages on issues raised (e.g., https://github.com/dcmi/schema.org/issues/9)
* the draft mappings themselves, in RDF/XML format, on GitHub (https://github.com/dcmi/schema.org)
* the mailing list, with a bit of everything.
The information and comments we need to consider in order to make the
mappings is spread all over and poorly linked. It is tedious even to pull these together
into an agenda.
Information about the properties and classes we are considering had to be
laboriously cut-and-paste into [1] -- and we will have no way of knowing if
the sources have changed if not by manually clicking on the links.
Finally, the RDF/XML format on GitHub is nice, because it is already in a
machine-readable form, but it is not friendly for users, so we would have
to find some way to generate a Web page from these mappings that people can
read and use. The RDF/XML format is also not ideal for citing in the
GitHub issue tracker, because URIs with line references will be thrown out
of sync as soon as we make edits.
Finally, it is still unclear how we will be able to collect comments on the
mappings on an ongoing basis.
Antoine, you suggested we might move the mappings from RDF/XML into RDFa [2]?
[1] http://wiki.dublincore.org/index.php/Schema.org_Alignment/Mappings_Details
[2] https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1204&L=dc-architecture&F=&S=&P=2541
Antoine: we could put these mappings into RDFa and point off to the discussion threads.
For example, we could have an HTML representation of URL above - plus pointers to GitHub
issue tracker and mailing list. We could add RDFa markup into the head of that section.
We could use the HTML of the wiki page as a starting point.
[3] http://wiki.dublincore.org/index.php/Schema.org_Alignment/Mappings_Details#schema:Organization_rdfs:subClassOf_dct:Agent
ACTION: Antoine and Tom to put wiki document Mappings_Details into RDFa.
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Issue 9: schemaorg type-properties and rdfs:domain (Bernard)
https://github.com/dcmi/schema.org/issues/9
Bernard: The Schema at RDFS.org is Michael Hausenblas's interpretation. It is
more or less endorsed by schema.org itself, because there is a link. But there
is also a rather inconspicuous schemaorg.owl schema, which is not in sync with
the larger schema.org activity. DanBri says that the implicit semantics at
schema.org are not as specific as at rdfs.org. He suggests we use schema.org.
I am perplexed; am unsure we can rely on something that is not explicit.
Issue: how will people use mappings that we publish? I just spoke with someone
who is using schema.org for a newspaper in French; they transform existing DC
into schema.org markup. Do we rely on something pragmatic? Turn DC into
Schema.org markup? Or do we say clearly we are using rdfs.org because schema.org
does not make available the equivalent?
Karen: It seems like a coin toss because we don't know which will be more stable.
We should pick the one we think is more stable.
Bernard: If you go to schema.org itself, there are no formal definitions, but
"types" and "properties" and "expected values", etc. but as DanBri explains,
these are not the formal semantics of RDFS domain and range.
These semantics are not expressed formally anywhere - except by Dan. I think
this is a shaky foundation to build on.
Some properties are defined with a domain of Person _or_ Organization, for
example. If you want to express this "or", it translates into OWL union.
Antoine: Agree, but Dan seems to be saying we should not consider these domain
statements, etc, as stable. Sceptical about the value of really precise
semantics in the DC context, because alot of properties are loosely defined -
just like Schema.org.
Bernard: But URIs used on both sides are the same (at schema.org and rdfs.org).
If you assert any equivalence between DC and Schema.org property, the URI you
use as subject of the triple is something that has a weird status now.
Schema.org does not provide a description, because the URI is not dereferenceable.
The only dereferenceable definition is given by Schema.org. If we make mappings,
we have to be explicit about where the semantics are defined. If not at rdfs.org,
where is there a formal definition?
Antoine: Okay with me to use rdfs.org. I will flag it if I see an rdfs.org definition
that is overcommitted - with semantics that are more constrained than the schema.org
version.
GordonD: +1 for using rdfs.org
Karen: I'm not sure how we could do this otherwise. How could we express equivalence
between things in RDF and things not in RDF?
Antoine: If equivalence is asserted between DC and non-RDF terms, implies that the
target propertiy "is a property" - an analogous problem.
Bernard: Antoine, this relates to HTTP Range-14. If the owner of the URI at
Schema.org does not declare the semantics of the URI, someone else will, and
this is exactly what is happening. Giving semantics to URIs not owned is
what is happening now. The other users of the URI will rely on the first
formal definition provided by whomever - not necessarily the publisher of
the URI. Of course, if Schema.org publishes formal definitions, we should
use them, but until then no choice.
Tom: If we were to decide otherwise, we would have to change the contents of [4],
which uses the formal definitions at rdfs.org.
[4] http://wiki.dublincore.org/index.php/Schema.org_Alignment/Mappings_Details
RESOLVED Use rdfs.org as basis of the mapping.
RESOLVED To Kirsten's question [5] -- how to add new proposals for mappings
-- the response is to wait until the RDFa file is done, then fold in new
proposals there.
[5] https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1202&L=dc-architecture&F=&S=&P=14738
--
Tom Baker <[log in to unmask]>
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