Re: Keeping R2RML free of Direct Mapping dependency (ISSUE-25)

On Tue, Apr 26, 2011 at 3:25 AM, Ivan Herman <ivan@w3.org> wrote:

> If the group decides not to make a reference to the Direct Mapping in in
> R2RML, then we still have to define what happens to those parts of the table
> that a specific R2RML file does not cover. In other words, we would have to
> define a default behaviour.


Ivan - Thanks for the response. The default behavior (as you described later
in your message) would be to not map those entities to RDF. It is my
understanding that this is what the current R2RML spec requires but I don't
think this is explicitly stated. The closest I can find at a quick skim is
section 1.4 "The output of an R2RML mapping is an RDF dataset. The RDF
triples in the dataset are the result of applying the mapping rules of each
TriplesMap to the rows of its logical table." I think this behavior (only
mapping entities that have been explicitly mapped) is legitimate. The use
cases that I have been working with require the R2RML mapper to have
explicit control over what is mapped.

Even under the scheme that allows the Direct Mapping constructs to be
invoked from an R2RML mapping I think that not mapping the entities would be
the default behavior. It would only be if the R2RML mapping indicated
"please use the Direct Mapping for RDB entity <X>" that the Direct Mapping
would be used.

-David