Re: [cti-cybox] CybOX Patterning question

[John-Mark Gurney <jmg@newcontext.com>]

Jason Keirstead wrote this message on Tue, Oct 04, 2016 at 11:49 -0300:
> If we make them greedy then can I break it apart with ( ) parens when I do
> not want that behaviour, and want to define multiple independent sequences?
> Because that is an important use case..

Yes, which ever way we pick, you can still do the other option w/ the correct
use of parens.  I provided examples on how that is possible.

> From:	John-Mark Gurney <jmg@newcontext.com>
> To:	cti-cybox@lists.oasis-open.org
> Date:	10/03/2016 06:51 PM
> Subject:	[cti-cybox] CybOX Patterning question
> Sent by:	<cti-cybox@lists.oasis-open.org>
> 
> 
> 
> Hello,
> 
> There is a discussion on Slack (and in the Patterning spec) about how
> Observation Operators and Qualifiers interact.  I'm bringing it here to
> have a full SC discussion.
> 
> Link to Patterning Spec:
> https://docs.google.com/document/d/1suvd7z7YjNKWOwgko-vJ84jfGuxSYZjOQlw5leCswPY/edit#heading=h.t32x0azc539r
> 
> The question is, do Qualifiers (REPEAT or WITHIN or START/STOP) apply to
> the immediately preceding Observation Expression, or to all preceding
> Observation Expressions?
> 
> The spec has it as not greedy, option 2 below.
> 
> 1) Qualifiers are greedy and apply to all preceding expressions (have low
> precedence than ALONGWITH/FOLLOWEDBY) : `[ a ] ALONGWITH [ b ] REPEAT 5
> TIMES` results in 5 a's and 5 b's (to get other result, you need to use: `
> [ a ] ALONGWITH ([ b ] REPEAT 5 TIMES)`)
> 
> 2) Qualifiers are not greedy and only apply to the immediately preceding
> expression (have a higher precedence than ALONGWITH/FOLLOWEDBY): `
> [ a ] ALONGWITH [ b] REPEAT 5 TIMES` results in 1 a and 5 b's. (to get
> other result, you need to use: `([ a ] ALONGWITH [ b ]) REPEAT 5 TIMES)`).
> 
> There is also the point that some qualifiers make sense to be greedy,
> REPEAT and START/STOP, while WITHIN be non-greedy as it doesn't make sense
> to apply to only one Observation Expression.  I would prefer NOT to split
> these as it will confuse writers and readers of these patterns.  Yes, they
> could be described w/ a simple precedence table, but that would just add
> another rule that people have to memorize.
> 
> I do not have a strong preference for one or the other.  I personally think
> that 2 makes slightly more sense, as if you write a long pattern w/
> multiple qualifiers, you'll end up using less parens than the other way.
> 
> Thanks for your input.

-- 
John-Mark