[delta-l] "Logical" combinations

Mike Dallwitz m.j.dallwitz at netspeed.com.au
Thu Jan 5 13:25:03 CET 2012


- From: Craig Robbins

> When encoding item attributes, ... how [are the DELTA connecting symbols
> '/', '&', and '-'] meant to be interpreted?

They should be interpreted in the same way as the words that they produce 
in natural-language descriptions: 'or', 'and', and 'to'. For example, with 
the character

#1. flowers <colour>/
        1. red/
        2. white/

the attribute 1,1&2 means 'Flowers red and white', whereas 1,2&1 means 
'Flowers white and red'. Although these are the same in a narrow, logical 
sense, the order might have some significance, for various reasons. For 
example, the predominate or more common value might be put first. 
Therefore, DELTA distinguishes these forms.

Note that if the characters states are reordered:

#1. flowers <colour>/
        1. white/
        2. red/

then the values must be reordered in the attribute, too: 1,1&2 becomes 
1,2&1. But the natural-language description stays the same: 'Flowers red 
and white'.

> [In] 1&2&3 ... '1' does not have a "connecting symbol" ... does '1' (in
> this example) have an /implied/ connecting symbol of '&'?

I presume you're asking this because you are thinking of storing a 
connecting symbol with each state value in a database. However, the 
connecting symbols are not associated with either the preceding or the 
following value; they are /between/ the values.

The easiest way to handle this in a database system might be to store the 
actual DELTA text string of the attribute, at least for 'complex' 
attributes as defined in the 'User’s Guide to the DELTA Editor'.

-- 
Mike Dallwitz
Contact information: http://delta-intkey.com/contact/dallwitz.htm
DELTA home page: http://delta-intkey.com


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