Re: [tag] Current issue with "TA for properties"

[Stephen Green <stephen.green@documentengineeringservices.com>]

I've not been quite convinced that there was a clear case for
putting the property definition in the prescription level. I'm
still a little uncertain about merely using a tag but it seems
better than overloading presription level so unless anyone
objects I will include this in another draft (along with some very
minor rewording Jacques has suggested offlist).

Best

Steve

2009/5/20 Jacques R. Durand <JDurand@us.fujitsu.com>:
> A medium technical issue with the current TAG draft:
>
> In section 3.3 "TA  for Properties":
>
> We recommend to mention the property ("medium-sized" ) in the Prescription
> element:
>
>
> Prescription Level: medium-sized:mandatory
>
>
> Because we want the prescription level to be associated with the definition
> of this property.
>
>
> [requirement 104] “A widget that weighs between 100g and 300g and is from 5
> to 15 centimeters long in its longer dimension, is a medium-size widget.”
>
>
>
> Suggestion: instead of this, use a tag for expressing the association of the
> TA to the property:
>
>
> Prescription Level: mandatory
>
> Tag: normative_property = medium-sized
>
>
> Rationale:
>
> - very close association between the Property and the Prescription level (as
> currently suggested) is a bad idea: it seems to suggest that the TA
> "widget-TA104-1" MUST evaluate to true (mandatory) for the property to be
> verified.
>
> But that does not work if  [requirement 104] has "or" instead of "and" :
>
> [requirement 104] “A widget that weighs between 100g and 300g OR is from 5
> to 15 centimeters long in its longer dimension, is a medium-size widget.”
>
> In that case we only want to indicate that the two TAs involved are related
> to the definition of this property, nothing more, as you could still satisfy
> the property even if you fail either TA. The Prescription level should only
> reflect the wording in the requirement, not be interpreted as a conformance
> statement.
>
>
>
> - a "normative property" should ultimately not be treated differently from a
> conformance profile. In both cases we don't want the Prescription level to
> be too closely associated with the profile or property (which may require a
> more complex combination of TAs, to be verified). Using a Tag is more
> appropriate for such a loose association, whcih has simply the value of an
> annotation (grouping) with no other formal semantics.
>
> - The TA could be associated with several properties.
>
>
>
> Jacques