Re: [tag] About Prescription levels

[stephen.green@systml.co.uk]

How about this example:

"The button MUST NOT have colors black and blue
together or red and green and grey together or red
and white and a color other than orange."

Negating this to allow for a positive prescription
level does seem problematic. The problem is the
'and', 'or', etc along with existing negation.

Isn't it a problem that

A AND B

when negated is

Not A OR Not B

when so many forget and write 'Not A AND Not B' (or at
least I sometimes have done while in my early programming
days).


Why not then just 5 values:

For MUST -- 'mandatory'
for MUST NOT -- 'not permitted'
for SHOULD -- 'preferred'
for SHOULD NOT -- 'preferred not'
and for MAY -- 'optional'

Then we can put simply, in prose without being forced
to use a logic expression like Not(A AND B):


"The button does have colors black and blue
together or red and green and grey together or red
and white and a color other than orange."

PL: 'not permitted'

-- 
Stephen D. Green

Partner
SystML, http://www.systml.co.uk
Tel: +44 (0) 117 9541606

http://www.biblegateway.com/passage/?search=matthew+22:37 .. and voice