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Subject: Re: [tag] coments on Section 3.7.2 "COmposition of Assertions" (V0.995)
- From: david_marston@us.ibm.com
- To: tag-comment@lists.oasis-open.org
- Date: Wed, 22 Oct 2008 15:05:01 -0400
I see a problem when a prerequisite
requires testing in order to determine eligibility. One can then build
a dependency chain of the tests: e.g., you can't apply tests derived from
TA 76345 until you have an outcome on any of a family of tests (list them
here) that will show that the prerequisite of 76345 has been satisfied.
Some of those tests may have their own prerequisites and hence dependencies,
etc.
Prerequisite: [the widget] is conformant
to Mini-Widget Small Box Specification 1.2
Predicate: [the widget] is conformant
to WidgetSpec 1.0
<SG> the main assertion is that such a small widget
is also a widget in that it conforms to the WidgetSpec 1.0
the way this TA
reads, the normative Source must be aligned with the Predicate: it should
be "Conformance clause to WidgetSpec
1.0" (exactly like in widget-TA109-1)
I think it reads that you
must already determine that the target is a Small Box 1.2 Mini-Widget before
you can even ask about whether it is a 1.0 Widget. Circular dependency?
<SG> Surely this is just another way of saying the
same thing:
"conformant to WidgetSpec 1.0" == "conforms
to the conformance clause of WidgetSpec 1.0"
That equivalence is true if
WidgetSpec 1.0 only has one class of product. Otherwise, it must say something
like "is a conformant [class] as defined by WidgetSpec 1.0".
The presence of the prerequisite means that
the TA only applies to widgets already known as confirming to Mini-Widget
Small Box spec:
<SG> I agree
The problem is the "already
known" part. I think this drives the debate about whether prerequisites
can be based on either (1) declarations from the product provider and (2)
measurable/testable properties of the implementation. A "type 2"
prerequisite, if as broad as "is a conformant widget" could still
exist in a formal structure of measured facts (predicates, as it were)
as long as the TAs for widgets include a final "summary" TA for
overall conformance.
I think you can see why I
wish this example used an orthogonal spec. The example I suggested is power
sources for portable devices. Specify that some but not all widgets are
portable, and certain portable ones must conform to the specs about power
sources.
.................David Marston
IBM Research
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