A way to generate PK-strings or new blank nodes

Hi there,

I am currently playing with R2RML, and experiences a few
difficulties while trying to implement a "Direct mapping"
generator as a R2RML graph. (using this mapping on an
INFORMATION_SCHEMA schema should generate the direct
mapping).

The main problem is to generate the row nodes. I don't
specially want to follow the PK-string defined into the
direct mapping document (it would be nice to do it, but I
don't think it is actually possible without using an SGBDR
specific construction). So I decided to simply use unique
IRIs or unique blank nodes, but this is no more
possible: because I don't know the fields into my tables,
I cannot create a template that will make only unique
values, and I cannot do it for blank node labels anymore.

A solution would be to have a construction such as:

rr:subjectMap [
  rr:termType rr:BlankNode;
];

(note the absence of rr:constant, rr:column and
rr:template properties)

The behavior would the be, for example, to generate a new
blank node with a reserved name such as "rrauto_X" where X
is a natural ...

Or perhaps does anybody know a way to generate the
PK-string using an R2RML mapping ? Please let me know ...

Best regards,

Fabian Pijcke