RegistryQuery query

[Patrick Dowler]

"A NOT_EQUAL B"  aka "A != B" aka "NOT ( A EQUAL B)" 

which agrees with Tony's assertion that NOT is a unary boolean operator.
You can negate any other boolean expression.

Patrick

On Tuesday 8 June 2004 15:00, Arnold Rots wrote:
> Unless you read NOT_EQUAL as a combination of a binary operator
> (EQUAL) and a unary operator (NOT):
> i.e., read "A NOT_EQUAL B" as "A EQUAL (NOT B)"
>
>   - Arnold
>
> Tony Linde wrote:
> > Isn't it usual that NOT is a unary operator which reverses the boolean
>
> value
>
> > of an operand and NOT_EQUAL (<> or !=) is a binary operator with the
>
> usual
>
> > meaning(s).
> >
> > Cheers,
> > Tony.
> >
> > > -----Original Message-----
> > > From: owner-registry at eso.org [mailto:owner-registry at eso.org]
> > > On Behalf Of Matthew Graham
> > > Sent: 08 June 2004 21:55
> > > To: Tony Linde
> > > Cc: registry at ivoa.net
> > > Subject: RegistryQuery query
> > >
> > >
> > > Hi,
> > >
> > > I have been looking at the QueryResource schema and was
> > > wondering about the "not" operand - is it supposed to be an
> > > existence operator or test whether a particular ResourceXPath
> > > is true or false? In either case the proposed syntax strikes
> > > me as being rather like Reverse Polish:
> > >
> > > <ResourceXPath> not
> > >
> > > or
> > >
> > > <ResourceXPath> not <value = true/false?>
> > >
> > > Is it actually supposed to be the <does-not-equal> operator,
> > > in which case can it be renamed to that?
> > >
> > > 	Cheers,
> > >
> > > 	Matthew
>
> ------------------------------------------------------------------------
> --
> Arnold H. Rots                                Chandra X-ray Science
> Center
> Smithsonian Astrophysical Observatory                tel:  +1 617 496
> 7701
> 60 Garden Street, MS 67                              fax:  +1 617 495
> 7356
> Cambridge, MA 02138
> arots at head.cfa.harvard.edu
> USA
> http://hea-www.harvard.edu/~arots/
> ------------------------------------------------------------------------
> --

-- 
Patrick Dowler
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