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

["Jacques R. Durand" <JDurand@us.fujitsu.com>]

Stephen:

I was indeed the one most in favor of doing this prefixing of the prescription level :-\ 
Realized that this does not work in general...
The tag appears to be the most flexible way: adding a new TA element might open a new can of worms. 
I believe actually that it is good to not relate tightly the prescription level to the "intent" of the TA (here a property), which may change or may be more relevant to a combination of Tas.
Let us discuss this next week.

Jacques

-----Original Message-----
From: stephengreenubl@gmail.com [mailto:stephengreenubl@gmail.com] On Behalf Of Stephen Green
Sent: Wednesday, May 20, 2009 12:21 PM
To: TAG TC
Subject: Re: [tag] Current issue with "TA for properties"

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

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