On 9/24/2013 8:51 AM, Kingsley Idehen wrote:
> The WHERE CLAUSE of SQL isn't a nirvana. It's a slot. (01)
More precisely, it has the expressive power of FOL. It supports
the Boolean operators AND, OR, and NOT. With the existential
quantifier and the option of nested WHERE clauses, that supports
first-order logic (but without functional expressions). (02)
That expressive power is the equivalent of Datalog for queries
and for views. A Datalog rule is the equivalent of a virtual
relation in SQL. (03)
When applied to any RDB (or the equivalent in RDF), those queries
can be evaluated in polynomial time. (04)
> My issue is all about what you can do within the slot when you
> have an entity relationship model oriented graph endowed with
> machine-comprehensible semantics. (05)
To say that SQL or Datalog expressions are just slots is highly
misleading. But I agree that E-R models are very useful. In fact,
type hierarchies and E-R diagrams are the two most widely used UML
diagrams. Together, they can represent most published OWL ontologies.
The other UML diagrams go far beyond OWL. And programmers know them. (06)
> SQL RDBMS products don't support Reference types as native data
> types -- its a silo by definition with an inability to semantically
> intermingle data across engines from different vendors (07)
The limitations of those products were recognized for over 30 years --
by all the major DB researchers, developers, and users. That was the
theme of the ANSI/SPARC conceptual schema in 1978. But that work ended
in a technical report instead of a standard -- because certain vendors
felt that standards would threaten their market dominance. (08)
> I specifically provided a SPASQL (SPARQL inside SQL) example to showcase
> what can be achieved in the SQL WHERE CLAUSE when you leverage SPARQL.
> If there is some concrete alternative to what I provided, I am sure
> someone could post and example just as I did. (09)
Prolog and other logic-based languages have been accessing both
relational and graph-based databases for over 30 years. (010)
Experian, for example, uses Prolog on huge data volumes to evaluate
everybody's credit worthiness. They process resources of every kind.
Unfortunately, Experian, by the nature of their business, are too
secretive to tell anybody exactly what they do and how they do it. (011)
> Sharing this presentation I stumbled upon based on its relevance to
> a variety of discussion threads on this list.
>
> [1]
>http://de.slideshare.net/kurzum/nif-20-tutorial-content-analysis-and-the-semantic-web (012)
I strongly support LOD and open standards. But this proposal claims
that NL content should be mapped to RDF + OWL. That teeny-tiny *silo*
may be useful for DBpedia -- but it's hopelessly inadequate for NLP. (013)
John (014)
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