Re: [ontolog-forum] Knowledge graphs by Google and Facebook

[William Frank <williamf.frank@xxxxxxxxx>]

On Sat, Jan 19, 2013 at 5:31 PM, Obrst, Leo J. <lobrst@xxxxxxxxx> wrote:

Relational databases are nearly always under the closed world assumption. There may be exceptions, but they are few.

I have never been able to understand this closed world stuff, except as a formal theory that was unnecessary and undesirable. I always thought that 'not' in a relational query meant 'not found', rather than 'not true' until somebody told me about 'closed worlds.'   And, I still don't know  why 'not found' doesn't work as well. The closed world "assumption" is so obviously FALSE, I ask, why should we make false assumptions,and why should we teach users of databases to think this way, when they speak to customers on the phone, as they increasingly seem to do. And it seems to me to be quite pernicious, Wasn't Big Brother always saying something along these lines?   Reading about it has never gotten me to the bottom of the matter in a doable amount of time.  Can somebody help me out with this?

Similarly, logic programming in general is under closed world assumption, though there are variants (well-formed semantics) and answer set programming (which can have negation operators under both CWA and OWA).

Thanks,
Leo

>-----Original Message-----
>From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-
>bounces@xxxxxxxxxxxxxxxx] On Behalf Of John F Sowa
>Sent: Saturday, January 19, 2013 3:45 PM
>To: [ontolog-forum]
>Subject: Re: [ontolog-forum] Knowledge graphs by Google and Facebook
...
>
>SQL and SPARQL can be used for either open world or closed world
>databases.  It is true that nearly all the stuff on the WWW is open
>world, but many, if not most relational DBs are also open world.
>





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William Frank

413/376-8167


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