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Re: Substantial comments on the DM Mapping

From: Michael Hausenblas <michael.hausenblas@deri.org>
Date: Mon, 8 Aug 2011 12:27:57 +0100
Cc: Eric Prud'hommeaux <eric@w3.org>, Juan Sequeda <juanfederico@gmail.com>, rdb2RDF WG <public-rdb2rdf-wg@w3.org>
Message-Id: <41C2F157-8AC9-46E8-A06B-8023638FE537@deri.org>
To: Ivan Herman <ivan@w3.org>


Thanks a lot for this feedback.


*This* is what I mean by prepare yourself ;)

Dr. Michael Hausenblas, Research Fellow
LiDRC - Linked Data Research Centre
DERI - Digital Enterprise Research Institute
NUIG - National University of Ireland, Galway
Ireland, Europe
Tel. +353 91 495730

On 8 Aug 2011, at 12:21, Ivan Herman wrote:

> Eric, Juan,
> as promised, these are the more substantial comments. I am no 100%  
> how you two divide up the work; I would expect most of the comments  
> would be handled by Eric except for the very last one...
> Cheers
> Ivan
> - The status of the document should reflect that this is last call.  
> Something like that should appear in the status section (text stolen  
> from another document):
> [[[
> This is a Last Call Working Draft and thus the Working Group has  
> determined that this document has satisfied the relevant technical  
> requirements and is sufficiently stable to advance through the  
> Technical Recommendation process.
> ]]]
> - It would be good to share the characterization of the direct  
> mapping and r2rml and how these two compare (answering the almost  
> inevitable question that the community would/will ask: why these  
> two?).
> The R2RM document currently says:
> [[[
> This specification has a companion that defines a direct mapping  
> from relational databases to RDF [DM]. In the direct mapping of a  
> database, the structure of the resulting RDF graph directly reflects  
> the structure of the database, the target RDF vocabulary directly  
> reflects the names of database schema elements, and neither  
> structure nor target vocabulary can be changed. With R2RML on the  
> other hand, a mapping author can define highly customized views over  
> the relational data.
> ]]]
> The same statement (well, modified for the DM case in terms of  
> 'companion') should maybe added to the DM document. The text that is  
> currently there is really not enough.
> - Section 2. The text currently says:
> "...RDF graph that is called the direct graph. This graph is  
> composed of relative IRIs that may be resolved against a base IRI"
> which seems to suggest that the RDF graph will have relative IRI-s  
> in their nodes. I do not think that is correct: an RDF graph always  
> uses absolute IRI-s. The usage of the base IRI is part of the  
> generation process and/or the specific serialization of the graph,  
> and not part of the final graph...
> - Section 2.5, generated turtle example: with the usage of @prefix,  
> the last few statements yield the subject as:
> <http://foo.example/DB/TaskAssignment/worker=7,project=pencil+survey_>
> Note the '_' character at the end. This contradicts 2.3 which would  
> yield:
> <http://foo.example/DB/TaskAssignment/worker=7,project=pencil+survey>
> I think the one in 2.5 is wrong.
> (b.t.w., as this is an informal section, it may be worth noting that  
> the '+' character in the URI stands for the encoding of the space  
> character)
> - Section 2.5: I do not think it is appropriate to keep issues in a  
> Last Call WD. The second issue is actually moot now, with both  
> formalisms in the document. The first issue should also be removed.
> - Section 3, definition row node: it says 'the row node is a  
> relative IRI...'. This is the same remark as above for the graph: a  
> node in an RDF Graph has an absolute IRI; the usage of the relative  
> URI is a generation/serialization artefact. What about
> "the relative IRI to define the node..."
> or something like that.
> - Section 3, the definition of the property IRI seems to contradict  
> the examples. Taking the very first example, the property IRI-s in  
> the example are of the form
> ... <http://foo.example/DB/People#fname> ...
> whereas, if I follow the specification here in section 3, I think I  
> would get:
> ... <http://foo.example/DB/People/fname#> ...
> I think the right one is the example, which also coincides with  
> entry [48] in A.4...
> Also, I am not sure the definition should refer to a primary key.  
> The property IRI generation should be valid for any column, and the  
> definition reads as if only primary keys were used...
> - Appendix B: the cross links should be redone. The target for the  
> link to Column IRI has been changed, the same for Table IRI, etc.  
> Essentially, all cross-links should be checked, and should point at  
> the normative definition.
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Monday, 8 August 2011 11:28:27 UTC

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