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Re: SQL delimited vs regular identifiers

From: Richard Cyganiak <richard@cyganiak.de>
Date: Mon, 7 Nov 2011 19:13:58 +0000
Cc: public-rdb2rdf-comments@w3.org
Message-Id: <66BE8144-05F6-4AF0-8692-5419E41EF908@cyganiak.de>
To: David McNeil <dmcneil@revelytix.com>
David,

The Note in Section 5 has been reverted to an earlier state:
http://www.w3.org/2001/sw/rdb2rdf/r2rml/#logical-tables

Can you please let us know whether this addresses your comment?

Thanks,
Richard


On 13 Oct 2011, at 18:13, David McNeil wrote:

> 
> ---------- Forwarded message ----------
> From: David McNeil <dmcneil@revelytix.com>
> Date: Thu, Oct 13, 2011 at 11:30 AM
> Subject: SQL delimited vs regular identifiers
> To: RDB2RDF WG <public-rdb2rdf-wg@w3.org>
> 
> 
> I have several comments/questions about this note in section 5 of the R2RML draft [1]
> 
> "Note that in R2RML, column name specified as an RDF plain literal or within curly braces, is considered a delimited SQL identifier."
> 
> 1) My reading of this is that a column or table name in an R2RML mapping, like: 
> rr:column "age"
> would be interpreted as a delimited identifier: "age", as opposed to a regular (un-quoted) identifier: age
> 
> For the case where SQL identifiers in the database are regular identifiers, this has the effect of making the identifiers used in the mapping case sensitive by default (since a regular identifier of AGE in the database would not match a delimited identifier of "age" from the mapping). In my experience most SQL identifiers are regular identifiers and users are accustomed to entering identifiers in a case in-sensitive manner. So it seems to me that it would be more useful if R2RML supported case in-sensitive identifier usage by default. This could be accomplished by interpreting RDF plain literals as regular identifiers.
> 
> 2) It is not clear to me how this matches the resolution identified in "ISSUE-35: Case sensitivity of SQL identifiershttp://www.w3.org/2001/sw/rdb2rdf/track/issues/35" [2]
> 
> 3) As far as I can tell this approach is not documented in the normative parts of the spec.
> 
> 4) Why does it call out "column name[s]", why not other SQL identifiers embedded in R2RML?
> 
> 5) How are users to enter a regular identifier as a SQL identifier in R2RML?
> 
> 6) Per the normative part of the spec, is the user expected to be able to enter a delimited identifier as:
> rr:column "\"age\""
> 
> 7) The grammar of the note needs some work.
> 
> I admit these are slippery ideas, so perhaps I am not analyzing it all correctly.
> 
> -David
> 
> [1] http://www.w3.org/2001/sw/rdb2rdf/r2rml/#logical-tables
> [2] http://www.w3.org/2001/sw/rdb2rdf/track/issues/35
> 
Received on Monday, 7 November 2011 19:14:29 GMT

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