Re: [ontolog-forum] ONTOLOG community event planning and scheduling sess

[Juan Sequeda <jsequeda@xxxxxxxxxxxxx>]

On Thu, Sep 12, 2013 at 8:33 AM, John F Sowa <sowa@xxxxxxxxxxx> wrote:

On 9/11/2013 10:48 PM, Juan Sequeda wrote:
> If you consider RDBMSs legacy systems, then we have the W3C RDB2RDF
> standards: Direct Mapping and R2RML, to bridge RDBMSs with the Semantic Web

Points to remember:

  1. RDBMSes are definitely *not* legacy systems.  They run the world
     economy today, and they'll continue running it for another 40 years.

Fair enough.

So what is the definition of legacy system? 

In my (short) experience, talking to real businesses and customers, many people consider RDBMSs as legacy systems. 

All in all, people want to bridge a previous technology (RDBMS) with new technology (Semweb). 

 

  2. RDB2RDF and Direct Mapping are throwbacks to ancient times of batch
     processing, and they only go in one direction.  They do *nothing*
     for interoperability.  In fact, they are *worse* than nothing,
     because they create an *illusion* of usefulness.

There are two modes of operation. ETL or Wrappers. 

With ETL, you have (if I understand correctly), what you are calling "batch processing". With wrappers, the data doesn't move. It continues to be in the RDBMS, and can be queried by SQL and SPARQL.

  3. The term NoSQL originally meant "no" as in "not exists".  But it
     quickly became an acronym for "Not only SQL".  Some of the most
     efficient NoSQL systems use SQL as their primary query language,
     but they implement SQL with new data structures and algorithms.

Our system, Ultrawrap, takes full advantage of the SQL infrastructure. We push down SPARQL optimization to the SQL optimizer. The result: the RDBMS successfully optimizes SPARQL and query execution of SPARQL vs SQL are comparable and sometimes equal.

More info: http://www.websemanticsjournal.org/index.php/ps/article/view/344

 

  4. The major vendors of *commercial* SQL-based and RDF-based tools have
     a far deeper and more successful understanding of interoperability:
     They support *both* SQL and SPARQL, and they enable them to run
     *concurrently* on the same data.

I agree. See above. 

 

Fundamental requirement:  Equal support for SQL and SPARQL.

I agree. See above.   

Recommendation:  Adopt Datalog (or a typed version of Datalog) as
the fundamental DB language, and specify the core of *both* SQL and
SPARQL in terms of Datalog.  But each of them has idiosyncratic
additions; they must be supported, but they should be deprecated.

I completely agree! And actually, it has been proven that SPARQL and non-recursive safe Datalog with negation have equivalent expressive power. Therefore, by classical results, SPARQL is equivalent from an expressive point of view to Relational Algebra (SQL). 

http://users.dcc.uchile.cl/~cgutierr/ftp/expressive-power-sparql.pdf

 

For further discussion of the issues, see the following article by
Michael Stonebraker in the Communications of the ACM:

http://www.labouseur.com/courses/db/Stonebraker-on-NoSQL-2011.pdf

The db directory of this website also contains other downloads that
address related topics:

http://www.labouseur.com/courses/db/

John

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