Re: A Direct Mapping of Relational Data to RDF is FPWD

My first reaction was that it might be a bit over-rigorous in this case:
sealed abstract class SQLDatatype   case class SQLInt () extends SQLDatatype   
case class SQLFloat () extends SQLDatatype   … 
case class SQLString () extends SQLDatatype
 
Using a sealed class here says that this is the complete set of possible data 
types.  That seems like painting yourself in a pretty small box when it comes to 
the richness of data types found in dbs in practice.  FYI, Revelytix is actually 
using Clojure for our implementation (although we considered Scala closely too). 
 

Some other comments:

1) I saw the requests for explanation of the #_ row IRIs on the list but I don't 
recall ever seeing the answer.  Easily could have been in the minutes that I 
didn't read though. :)   I saw the hash-vs-slash note in the spec but is the 
trailing _ just to have something after the #?

2) I was surprised at a first glance to see ,'s in the compound key IRIs but 
it's equivalent to the same information we're using in our subject IRIs.  

3) We were not smart enough to use blank nodes for tables w/o primary keys and 
just punted on the issue but I think the blank node solution works well.

4) We went back and forth on what to do when having multiple unique keys in a 
table and whether to create multiple "same as" identifiers in that case to the 
primary key subject IRI.  You're consistently using the PK subject IRI which I 
think is the right choice for the direct mapping.  I haven't looked at R2RML 
enough yet to understand the range of choices there.

5) Issue (formalism-model) refers to sections 5 and 6 but those should be 3 and 
4.  Personally, I find the definition to be easier to read than the rules, but 
that's probably due to familiarity.  

6) It would be really nice to see an equivalent R2RML that produces the direct 
mapping.



________________________________
From: Alexandre Bertails <bertails@w3.org>
To: Eric Prud'hommeaux <eric@w3.org>
Cc: Alex Miller <alexdmiller@yahoo.com>; Michael Hausenblas 
<michael.hausenblas@deri.org>; RDB2RDF WG <public-rdb2rdf-wg@w3.org>
Sent: Thu, November 18, 2010 12:53:14 PM
Subject: Re: A Direct Mapping of Relational Data to RDF is FPWD

On Thu, 2010-11-18 at 12:43 -0500, Eric Prud'hommeaux wrote:
> * Alex Miller <alexdmiller@yahoo.com> [2010-11-18 08:26-0800]
> > Looks great all.  I've just skimmed through it but it's interesting seeing 
>how 
>
> > you've handled certain issues in similar and different ways from what we've 
>done 
>
> > at Revelytix. 
> > 
> > We are interested in supporting these specs moving forward although I'm not 
>sure 
>
> > yet when we'll start working on it.  If things move along favorably we may 
>also 
>
> > be able to open source the implementation at some point.
> > 
> > I was surprised (and delighted) to see the Scala syntax in the spec too. :)  

> 
> It's perhaps over-rigorous for the purposes of presentation (uses case
> classes rather than type= to ensure type safety). The source:
>  
>https://dvcs.w3.org/hg/FeDeRate/file/tip/directmapping/src/main/scala/DirectMapping.scala
>

Case classes are the Scala algebraic datatype implementation. They
define both types (the classes) and type injectors (the constructors).

Sure, we should split the formal definition from the type-safety proof.

Pattern matching + type-checking is not "over-rigorous" when you gain
such confidence in your formalism.

Alexandre.

> 
> is editable by RDB2RDF members.
> 
> > ________________________________
> > From: Michael Hausenblas <michael.hausenblas@deri.org>
> > To: RDB2RDF WG <public-rdb2rdf-wg@w3.org>
> > Sent: Thu, November 18, 2010 10:06:29 AM
> > Subject: A Direct Mapping of Relational Data to RDF is FPWD
> > 
> > 
> > All,
> > 
> > Congrats to the team, esp. a big thanks to the editors - "A Direct Mapping
> > of Relational Data to RDF" [1] is now published as FPWD.
> > 
> > Cheers,
> >       Michael
> > 
> > [1] http://www.w3.org/TR/rdb-direct-mapping/
> > 
> > -- 
> > 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
> > http://linkeddata.deri.ie/
> > http://sw-app.org/about.html
>