Regards
 
Steve Hanson
Architect, IBM DFDL
Co-Chair, OGF DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve Hanson/UK/IBM on 11/08/2015 16:27 -----

From:        Michele Zundo <michele.zundo@esa.int>
To:        Mike Beckerle <mbeckerle.dfdl@gmail.com>
Cc:        Steve Hanson/UK/IBM@IBMGB, Maurizio De Bartolomei <Maurizio.De.Bartolomei@esa.int>, Montserrat Piñol <mpinol@eopp.esa.int>, "Rui Mestre (DME)" <rui.mestre@deimos.com.pt>
Date:        18/05/2015 08:47
Subject:        Re: [DFDL]: First Release of DFDL4S Parser Library

---

Thanks Mike,

we will add this to our list to be considered/noted.

However reading your explanation (NB I’m NOT at all an XPath expert) it seemed you
had some good reason for avoiding longer than 1 path, so I would like to avoid our DFDL4S
project results in an over-complication of the DFDL implementation/use of Xpath
unless there are other reasons/users/rationale requiring this feature.
(btw the syntax is still weird-ish:  “intersect” reminds me of Venn Diagrams…)

As a project manager I always evaluate solutions and their cost vs the benefit they bring,
and I believe the DFDL community should keep this is mind.

Michele

PS The syntax above anser to the question “belongs to” , would there be any way to express ranges of values then ?



On 15 May 2015, at 16:24 , Mike Beckerle <mbeckerle.dfdl@gmail.com> wrote:

Just a few comments on DFDL4S, and also thank you to Michele and team for the presentation on Tuesday.

I think all the issues in the spreadsheet are fairly easily fixed in that they are not major changes to DFDL4S, and would bring it into much closer compliance with the DFDL spec.

The exception is the XPath limitations where DFDL4S has gone beyond what XPath 2.0 allows and invented new syntax for expressing set membership requirements.

So I took a look, and XPath 2.0 has a set intersect operator:  ns1 intersect ns2 => ns3

This isn't in DFDL today, but might be usable to achieve the set membership test; however, it requires use of XPath node sequences of length greater than 1, which DFDL has avoided mostly. I say mostly as there are XPath expressions that return node sequences of length greater than 1 and those can be arguments to fn:count(...) for example.

So far in DFDL such node sequences cannot "leak out" of the XPath expression into DFDL elements, and I think the usage in DFDL4S is similar in that these node sequences would be needed only to check for set membership, so the result is just a boolean as part of an assert/discriminator.

We should examine whether XPath 2.0 set intersection is enough to meet the need.

I believe the expressions would be something like:

     fn:exists( . intersect (123, 456, 789, .... many more items....) )


- mike beckerle


Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com
Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy


On Tue, May 12, 2015 at 10:45 AM, Michele Zundo <michele.zundo@esa.int> wrote:
for reference,
here a summary of the reported problem in an excel sheet.

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-----------------------------------------
Michele Zundo

Head of Ground System Definition and Verification Office
EOP-PEP
European Space Agency, ESTEC
e-mail: michele.zundo@esa.int











-----------------------------------------
Michele Zundo

Head of Ground System Definition and Verification Office
EOP-PEP
European Space Agency, ESTEC
e-mail: michele.zundo@esa.int








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