RE: ISSUE-3

Thanks Juan...

Tomorrow we are continuing presentations.  It might be a good idea to use email to exchange thoughts till we are done with the presentations next week.

One observation that I have which is kind of border line is the notion of R2RML supporting SQL DDL statements.  I think what we mean is RDFS/OWL equivalence to SQL DDL statements.  In other words, we are not creating SQL table but rather creating a class that maps an existing SQL table to the RDF world, etc..

If the above makes sense, one possibility is to have a table with 3 columns: SQL column (DDL statement): RDFS column (equivalence): OWL column (equivalence).  In the SQL column you would have create table, then in OWL the equivalent is to create a class, etc...

Ahmed

From: Juan Sequeda [mailto:juanfederico@gmail.com]
Sent: Monday, November 23, 2009 19:22
To: Ezzat, Ahmed
Cc: Marcelo Arenas; Sören Auer; Michael Hausenblas; Harry Halpin; RDB2RDF WG
Subject: Re: ISSUE-3

I have now updated the list and added justification

http://www.w3.org/2001/sw/rdb2rdf/wiki/Requirements/DDLCoverage

I have based this on our previous work [1] and a technical report of ours which is a survey of different approaches that take DDL and convert it to an ontology [2].

Looking forward to a discussion about this tomorrow.

[1] http://www.springerlink.com/content/mv58805364k31734/
[2] ftp://ftp.cs.utexas.edu/pub/techreports/tr09-04.pdf


Juan Sequeda, Ph.D Student
Dept. of Computer Sciences
The University of Texas at Austin
www.juansequeda.com<http://www.juansequeda.com>
www.semanticwebaustin.org<http://www.semanticwebaustin.org>

On Mon, Nov 23, 2009 at 6:09 PM, Juan Sequeda <juanfederico@gmail.com<mailto:juanfederico@gmail.com>> wrote:
I'm sure we will all have different points of views and opinions on this.

For example, the way we have done this (and we have shown this in our dexa paper [1]): We have mapped the create table to classes, except if the tables are binary relations, then they would map to object properties. How do we automatically do this? Reading the data dictionary or using describe operation.

I apologize for being a bit behind on this but I've been under the weather. I'm in the processing of finishing the list and I will take Ahmed's suggestion of writing justifications. We can then discuss this tomorrow.

[1] http://www.springerlink.com/content/mv58805364k31734/

Juan Sequeda, Ph.D Student
Dept. of Computer Sciences
The University of Texas at Austin
www.juansequeda.com<http://www.juansequeda.com>
www.semanticwebaustin.org<http://www.semanticwebaustin.org>


On Mon, Nov 23, 2009 at 11:48 AM, Ezzat, Ahmed <Ahmed.Ezzat@hp.com<mailto:Ahmed.Ezzat@hp.com>> wrote:


Here is my 2 cents:

The format of the information Juan is collecting needs to be modified.  I do not know if Juan read his email or not?  The list he is collecting is the list of features that the mapping language needs to support on the SQL side, i.e., ability to find out the PK for a given relation R; this is doable using DESC (describe) operation. I asked Juan to put usage scenarios for each item suggested on his page.  For example, scenario where creating a table is needed?  I did not want to go and edit the format of the page, and instead asked Juan to do that. Then myself and others can edit content.

There is another dimension to the mapping issue on the other side, which is not part of what Juan is doing, i.e., RDFS or OWL usage of the information you get from the RDBMS side.

Ahmed


-----Original Message-----
From: Marcelo Arenas [mailto:marcelo.arenas1@gmail.com<mailto:marcelo.arenas1@gmail.com>]
Sent: Monday, November 23, 2009 07:56
To: Ezzat, Ahmed
Cc: Juan Sequeda; Sören Auer; Michael Hausenblas; Harry Halpin; RDB2RDF WG
Subject: Re: ISSUE-3

Hi,

I am a bit confused about what we mean by "supporting a feature" of
DDL.  Assume that we are given a relation schema R(A, B) where A is
the primary key of R. The list says that primary keys should be
supported,  so should attribute A be a primary key of R(A, B) in the
RDF representation of this database? The problem with this is that
there is no way to enforce a key in RDF (RDFS). Are we just going to
describe in RDF that A is a primary key without enforcing it?
What about OWL? Are we planning to use owl:FunctionalProperty to
indicate that A is a primary key? Thanks!

All the best,

Marcelo

2009/11/18 Ezzat, Ahmed <Ahmed.Ezzat@hp.com<mailto:Ahmed.Ezzat@hp.com>>
>
>
> Hi Juan,
>
> You can approach this problem from different angles. Request: on the discussion page as an example:
>
> Tables item:
>
> Create Table
> Must be supported
>
>
> Let me suggest one of two formats: you can list for the Table bullet: create table, delete table, alter table, describe table or just list the ones you want to support?  I see as an example Describe table is the obvious one as a must.
>
> In either scenario you want to adopt, please have next to any DDL statement you want a justification, i.e., scenario(s) justifying its use.
> Thanks,
>
> Ahmed
>
> Ahmed K. Ezzat, Ph.D.
> HP Fellow, Business Intelligence Software Division
> Hewlett-Packard Corporation
> 11000 Wolf Road, Bldg 42 Upper, MS 4502, Cupertino, CA 95014-0691
> Office:      Email: Ahmed.Ezzat@hp.com<mailto:Ahmed.Ezzat@hp.com> Off: 408-447-6380  Fax: 1408796-5427  Cell: 408-504-2603
> Personal: Email: AhmedEzzat@aol.com<mailto:AhmedEzzat@aol.com> Tel: 408-253-5062  Fax:  408-253-6271
> From: Juan Sequeda [mailto:juanfederico@gmail.com<mailto:juanfederico@gmail.com>]
> Sent: Wednesday, November 18, 2009 7:00 AM
> To: Sören Auer
> Cc: Michael Hausenblas; Harry Halpin; RDB2RDF WG; Ezzat, Ahmed
> Subject: Re: ISSUE-3
>
> On Tue, Nov 17, 2009 at 3:32 PM, Sören Auer <auer@informatik.uni-leipzig.de<mailto:auer@informatik.uni-leipzig.de>> wrote:
> Michael Hausenblas wrote:
> Though I see your point, DDL is the most general form of what we are talking
> about, here, covering data model elements
>
> I actually think DDL is not a very general form, but rather a very specific language for creating and manipulating relational schema objects.
>
>
> IMO, we should stick to the specifics. Hence, using DDL should be appropriate.
>
>
> (for sure DROP, ALTER is not in
> scope, but this is a no-brainer, I guess ;)
>
> Ok, but DDLs consist *only* of such statements, cf. e.g.:
>
> http://dev.mysql.com/doc/refman/5.1/en/sql-syntax-data-definition.html
>
>
> What is missing from that list, that we should take in account?
>
> I'm fine with DDL and think we have used it in the discussion throughout as
> such ...
>
> We can use the term DDL if everybody in the group got used to it, but from a conceptual point of view I think this is wrong and in order to avoid confusion with the outside world we should rather talk about /data model elements/ or /schema objects/.
>
> I think we can combine the two in this list that we are going to make. But we should also be on the same page. I see that you have Foreign Key, Integrity Constraints and Referential Integrity separate. Why? Aren't referential constraints a subset of integrity constraints. And a foreign key is a referential constraints. Those shouldn't be separate, but express them as subclasses.
>
> Sören
>
>