Re: Comments on Eric's Section 2

Richard,

Have you seen the new version:
http://www.w3.org/2001/sw/rdb2rdf/directGraph/alt

<http://www.w3.org/2001/sw/rdb2rdf/directGraph/alt>For the record, it was
not Marcelo/Juan's decision to fork document in the first place.


Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com


On Sat, Nov 6, 2010 at 11:13 PM, Richard Cyganiak <richard@cyganiak.de>wrote:

> All,
>
> I'm travelling and a few days behind the latest RDB2RDF news and continue
> to be baffled by events, especially the decision by Ashok and Thomas to
> abandon work on Eric's version of the direct mapping document in favour of
> the Juan/Marcelo version.
>
> I had a checkout of Eric's version and reviewed it while on the plane,
> which now apparently was a waste of time, but I'll share the comments
> anyway.
>
> Having read both documents, I think that Eric's is better written, gets the
> same information across in a more concise and accurate way, and has just
> sufficient examples to make everything clear. It deals with corner cases
> that are not addressed in the /alt version. Altogether I think that it's
> superior to the /alt document. I still don't understand why Juan and Marcelo
> have forked the document in the first place, but seriously I don't think
> that their changes have led to a superior Section 2 -- their version simply
> says the same things in a generally harder-to-digest style in more words.
>
> For the record: If the issues that I list below can be addressed, along
> with the three from my other email I sent earlier, then I support
> publication of an FPWD that consists of:
>
> - Eric's sections 1 and 2
> - followed by Eric's set semantics based formal approach
> - and Juan/Marcelo's datalog based formal approach
> - with an issue box explaining that both of these are work-in-progress
> candidates for the formal semantics.
>
> And that's the last thing I intend to say about the direct mapping thingy
> until the three editors have managed to present the WG with a single version
> of the document endorsed by all of them.
>
> Best,
> Richard
>
>
> Comments on Eric's draft
>
> 1. Section 2.1 is IMHO unnecessary and confuses more than it helps. I would
> move its first two sentences into the Introduction, and remove the rest, in
> particular the SPARQL example. The same goes for the SPARQL example in 2.4,
> I would remove it. SPARQL query evaluation is a completely different topic
> and requires a ton of knowledge that is not essential for understanding the
> default mapping, so I honestly don't see how this helps the average reader.
>
> 2. Section 2.2: The predicate for reference triples is described as: “an
> IRI composed of the stem, table name and column name and value for each
> column in the foreign key”. I don't understand why it says “and value”? The
> object is described as: “the subject created for the referred triple”. Do
> you mean “referenced row”?
>
> 3. Please provide a rationale for the “#_” at the end of generated IRIs in
> the text. In my opinion, this is entirely unnecessary and a useless
> complication. I see there is an issue box for that in the document, that's
> great, but if you want to have the “#_” thing in the FPWD then there should
> be text stating why it is necessary. My proposal for FPWD would be to
> s/#_//g and state in the issue box that this is subject to more discussion.
>
> 4. Inconsistency: Section 2.2 states that predicate IRIs have hashes, while
> all the examples have slashes.
>
> 5. You should define the terms “row IRI” or “row identifier” and “column
> IRI”, and use them throughout, instead of saying sloppy things like “a IRI
> composed of the stem, table name and column name” or “the subject of the
> referenced row”. I think this is done pretty well in the directGraph/alt
> draft.
>
> 6. Why a reference to [SQL99]? I thought we had agreed to use SQL Core
> 2008? You can copy the reference from the R2RML draft.
>
> 7. Both “URI” and “IRI” are used. I suppose it should be “IRI” everywhere?
>
> 8. In order to have an improved narrative in the section titles, I propose
> splitting 2.2 into one section “Identifiers for rows and columns” and one
> section “Row mapping rules”. (Not essential for FPWD)
>
> 9. Section 2.5: “Hierarchies” can refer to many things in an SQL context,
> so it's a bit hard to figure out what the section refers to. The first
> sentence should perhaps talk about “hierarchies of tables that represent
> specializations of the same concept” or something similar. The People table
> should perhaps be removed from the example, because it is not relevant to
> the example and makes understanding the relevant parts of the example
> harder.
>
> 10. Given that the question of many-to-many table mappings is an open
> issue, there should be at least a section about it that is empty except for
> an issue box. (I have more to say on this topic, but don't expect that
> discussion to be resolved before FPWD)
>
> 11. See my comments to Juan and Marcelo asking for inclusion of table IRIs
> and of a triple that associates each row to its table. I'd really like to
> see a proposal for this in the FPWD, but at least an issue box would be
> essential. I note that the directGraph/alt version already has this.
>
>
>