Re: Request for comments: Breaking down the datatype mapping problem (ISSUE-69)

Richard - Thank you for breaking this complex issue down. Here at
Revelytix, we spent some time reviewing the issues and came up with the
following responses (shown inline below).

-David

On Tue, Nov 15, 2011 at 2:51 PM, Richard Cyganiak <richard@cyganiak.de>wrote:

> == Should mapped literals be in canonical form? ==
>
> So, when a DOUBLE is mapped to a literal, is it ok to produce
> "100.0"^^xsd:double or does it have to be the canonical "1.0E+2"?
>

R2RML should not mandate that canonical forms are produced.

== Should data be C14N'd before used in IRI generation? ==
>

There must be a way to make IRIs canonical. Seems that this can be done
either implicitly (the R2RML processor does it automatically) or explicitly
(by providing some kind of canonicalize function for the user to invoke).
Even if there is an R2RML prescribed canonical IRI form, the user needs to
be able to override this to produce exactly the IRI they want/need, without
regard for what the canonical IRI form would be. This could be as simple as
the user can produce an exact string to use as an IRI.

== How should datatype overrides be handled? ==
>
>
The spec currently says that the canonical string value from SQL is
> directly used, without mapping to an XSD form.


Are there cases when the canonical SQL string value does not produce a
valid XSD value for the target XSD type? If so, then it does not seem
acceptable to just use the canonical SQL string value.

== Should canonical forms be SQL canonical or XSD canonical? ==
>

We do not think that R2RML needs to define canonical forms for the output
values.

== Should unknown vendor-specific types be mapped to plain literals? ==
>

It seems fine for these to be plain literals by default, but we can't
mandate that because an implementer may provide a way to map a user defined
type to something other than a plain literal.


> == Should “recipes” for converting the SQL forms to XSD be presented? ==
>

This seems good to do in a non-normative fashion.

== Should the “recipes” be normative? ==
>

No.