Re: [ubl-dev] Re: Test Assertions for UBL Calculation Model? Re: Re: [ubl-dev] Basic Invoice Exploration

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

Hi Ken

The WS-I-esque executable test assertion xpath profile from
the way it is looking doesn't include that 'eq' - it is implicit.
That makes the assertions easier to read and interpret and
most of all to execute. I guess the implicit 'eq' becomes part
of the xpath profile spec itself so when you say

...
<target>doc($invoice-instance)</target>
...
<predicate lg="xpath2">sum( ../cac:TaxSubtotal/cbc:TaxAmount )</predicate>
...

the 'lg="xpath2"' binding attribute includes the 'eq' implictly by
it being defined as part of the profile spec semantics for 'xpath2'
code. A few other things like that would be defined in the xpath
profile spec too, like how test assertion variables are expanded
within the expressions where they are used.

We are keen to standardise such a profile, following on from
the TAG TC work on the markup (which we think needs to be
standardised too, to provide a good foundation for the profile).
We haven't firmly decided which standards organisation yet.
I guess UBL can just get going with its own profile and convert
perhaps (for tool support sake, at least) later when the time is
right. That might provide feedback for TAG TC and what ever
ensues regarding XPath profile work.

Glad you're getting into this.

Best

Steve

Stephen D Green



2009/6/24 G. Ken Holman <gkholman@cranesoftwrights.com>:
> At 2009-06-23 21:36 +0100, Stephen Green wrote:
>>
>> I added to wiki what could be a possible start on which entities
>> need the calculation assertions
>
> I have taken your examples and I've proposed a pro-forma use of the wiki to
> express the needed test assertions:
>
>  http://wiki.oasis-open.org/ubl/Example_Calculation_Models#proforma
>
> ... and fleshed it out with your first examples here:
>
>  http://wiki.oasis-open.org/ubl/Example_Calculation_Models/Invoice_Tax_Total
>
>> I realise it's a little different to your proposed way forward Ken.
>> I'm more inclined to think the way to go is to set up a project
>> for assertions about the calculation model which feeds directly
>> into the UBL TC and its process for authoritative approval
>> rather than start with a more distant model like the OIO-UBL one
>> which might be seen as a customisation model rather than
>> official UBL TC one.
>
> One ramification of using an assertion (with true/false results) is that the
> expression doesn't really look like a calculation, though of course it
> incorporates the calculation.
>
> Whereas I originally had:
>
>  sum( ../cac:TaxSubtotal/cbc:TaxAmount )
>
> ... to make that into an assertion it has to read:
>
>  . eq sum( ../cac:TaxSubtotal/cbc:TaxAmount )
>
> Now that isn't a big change, and I can live with it, but it changes the
> "feel" of the document.
>
> I can live with it because as a programmer, if I see the test condition I
> can infer what I have to do to make the test evaluate to true.
>
> And, it means that if someone has a TA engine they could run their generated
> instances through the TA engine and get a report that they've met the
> conditions.
>
> When it comes time to write the HISC document, we'll have to explain the
> perspective of the calculation model documentation as one of "confirming the
> calculation model has been followed" rather than "the steps of calculation".
>
> Jaymuz (and others) ... do you feel that test assertions can effectively
> document what you need to implement in your systems?
>
> Stephen ... can you improve on the pro-forma and examples based on your
> previous work with test assertions?  On the cover page I've assumed the
> expression language is XPath 2.0 and I've left the identification of the
> assertions to the step when we assemble them into our document.
>
> . . . . . . . . . . . Ken
>
> --
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