Output dataset section

[dachafra]

@pmaria I don't know why output-dataset was included in #244, but please, use this PR to review the whole section.

[pmaria]

The output dataset section is missing descriptions on multivalued term maps and on language maps and datatype maps.

[dachafra]

Descriptions of datatype/language maps and multivalues are provided

[dachafra]

@pmaria can we merge this PR?

[pmaria]

Some notes on parts of the text that were merged earlier and I cannot comment on in this PR:

line 93 and 94. The mentions of [=URI=] can be left out, since a URI is an IRI.

I notice in the Adding Triples to the Output Dataset section two points that are new compared to R2RML:

5. RDF graphs MUST NOT contain duplicate triples. Adding multiple identical triples to the same graph has the same effect as adding it once.

I cannot recall discussing this in the group. But I do not agree with this point. Deduping does not matter in many cases, and should depend on the implementation and the use case.

6. The scope of blank nodes is limited to the output dataset being generated.

This is true, but seems somewhat misplaced in this section. I think it would make more sense in the Generated RDF Term of a Term Map section.

[dachafra]

Both points you mention @pmaria are included in R2RML, see last sentence of R2RML spec 11.1, but, indeed, the scope of BN is not in this sect. I'll move it to the corresponding one with a reference.