I agree with Michael ... the key point back on the original topic (IIRC at this
point) is that these meanings of NULL seem to tend more toward OWA than CWA,
and CWA was the big complaint being levied against RDBMS/SQL. (01)
[Btw and way not important ... hopefully a "fun fact" type of thing for those
who care to spend the time: I was the developer of a very early (~1976) RDBMS
for real-time operating environments ... "RTFILE", named for the DEC RT-11 OS
at the time, later ported to many other environments from PCs to supercomputers
... niche product with modest commercial success (for the time) in the
engineering, academic, and military segments ... product rights eventually sold
(cheaply) to a large telco and I went to work for Oracle ... main claim to
fame, however, was a hand-written note from Niklaus Wirth who used RTFILE at
ETH (probably very briefly), "RTFILE ist wunderbar!".] (02)
Cheers,
BobN (03)
-----Original Message-----
From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Michael Brunnbauer
Sent: Tuesday, January 22, 2013 12:13 PM
To: [ontolog-forum]
Subject: Re: [ontolog-forum] Knowledge graphs by Google and Facebook (04)
Hello Ed, (05)
On Tue, Jan 22, 2013 at 11:51:28AM -0500, Barkmeyer, Edward J wrote:
> At the risk of sounding like an old pedagogue, you might consider reading a
>Ted Codd paper from about 1980 on the possible interpretations of Null.
> My recollection is that he identified at least 4 possible interpretations:
> 1) No value is meaningful (the property does not apply to things with
>whatever other properties are documented)
> Example: a person whose marital status is "single" does not have a value
>for "spouse"
> 2) No value in this instance (the thing does not have an instance of this
>property)
> Example: a person may have no value for "mobile phone number" (by not
>having the service)
> 3) The value should exist but is not known (no one entered this datum)
> Example: a missing "date of birth"
> 4) Whether there is a value is unknown
> And there is a further state that we now sometimes see:
> 5) The value has been redacted. It may be in the database, but it is not
>in the query result, because the requester does not have the authority to ask
>for it (in this case).
>
> And there may well be others. "Null" is a Humpty Dumpty word. (06)
This Humpty Dumpty word seems to have a lot of use cases. Looks quite useful
to me (and has been in RDB projects). (07)
Do current RDBs actually behave differently regarding Null ? Otherwise I would
not see any problem. I don't care a bit about semantics as long as my tool has
a well defined behavior. (08)
Regards, (09)
Michael Brunnbauer (010)
--
++ Michael Brunnbauer
++ netEstate GmbH
++ Geisenhausener Straße 11a
++ 81379 München
++ Tel +49 89 32 19 77 80
++ Fax +49 89 32 19 77 89
++ E-Mail brunni@xxxxxxxxxxxx
++ http://www.netestate.de/
++
++ Sitz: München, HRB Nr.142452 (Handelsregister B München)
++ USt-IdNr. DE221033342
++ Geschäftsführer: Michael Brunnbauer, Franz Brunnbauer
++ Prokurist: Dipl. Kfm. (Univ.) Markus Hendel (011)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J (012)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J (013)
|