[DFDL-WG] do we allow indexing of non-array, non-optional

[Mike Beckerle]

Withdrawn - Section 2.6 makes it clear these are processing errors, not
schema definition errors; hence, the expression 'x[...]' is allowed.

...mikeb

Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
www.tresys.com
Please note: Contributions to the DFDL Workgroup's email discussions are
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On Mon, Nov 17, 2014 at 1:36 PM, Mike Beckerle <mbeckerle.dfdl at gmail.com>
wrote:

> We need to create an action item for this topic:
>
> In minutes of 2014-10-28 we took the position that 'x[1]' is allowed on
> scalars, and implementations can warn.
>
> However,....
>
> I just spotted this language in the latest DFDL spec, section 2.6
>
> •    Expression Errors
>
>    - Indexing of non-array non-optional element
>
> Example: x[1] when x is declared and has both minOccurs="1" and
> maxOccurs="1" explicitly, or by not stating either or both of them.
>
> Oops...
>
> So it appears we already took a position on whether x[1] is allowed for
> scalars. It's not. It's a schema definition error.
>
> However, this wording suggests x[1] allowed for optional elements - and
> this is redundant as just 'x' would be sufficient. To me that's ok, as when
> dfdl:occursCountKind='parsed' we don't use maxOccurs anyway, so any
> non-scalar is in fact treated as an array.
>
> The issue here of course is not about the constant expression '1', but
> e.g., 'x[$myVar]', when $myVar might or might not have value 1 at runtime.
> In general you cannot tell.
>
> If we believe there should be additional mention of this behavior later in
> the spec in section 23, then that could be added, but I don't think we
> should change this aspect of DFDL. I believe it actually makes
> implementations harder if one blurs the lines between scalars and
> arrays/optionals. Right now they are reasonably cleanly separated.
>
> ...mikeb
>
>
>
> 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
> <http://www.ogf.org/About/abt_policies.php>
>
>
> On Tue, Oct 28, 2014 at 2:06 PM, Steve Hanson <smh at uk.ibm.com> wrote:
>
>> Agreed on call not to add any extra restriction but a DFDL implementation
>> is free to issue a warning if it detects such usage.
>>
>> Regards
>>
>> Steve Hanson
>> Architect, *IBM DFDL*
>> <http://www.ibm.com/developerworks/library/se-dfdl/index.html>
>> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
>> IBM SWG, Hursley, UK
>> *smh at uk.ibm.com* <smh at uk.ibm.com>
>> tel:+44-1962-815848
>>
>>
>>
>> From:        Tim Kimber/UK/IBM at IBMGB
>> To:        dfdl-wg at ogf.org
>> Date:        16/10/2014 05:58
>> Subject:        Re: [DFDL-WG] do we allow indexing of non-array,
>> non-optional
>> Sent by:        dfdl-wg-bounces at ogf.org
>> ------------------------------
>>
>>
>>
>> I don't think we should depart from the standard XPath rules any more
>> than is necessary. Sometimes an XPath author will put [1] after every
>> scalar element as a matter of habit, because it makes the execution of the
>> expression faster ( in some XPath processors ).
>>
>> regards,
>>
>> Tim Kimber,
>> Technical Lead for IBM Integration Bus Healthcare Pack
>> Hursley, UK
>> Internet:  kimbert at uk.ibm.com
>> Tel. 01962-816742
>> Internal tel. 37246742
>>
>>
>>
>>
>> From:        Mike Beckerle <mbeckerle.dfdl at gmail.com>
>> To:        "dfdl-wg at ogf.org" <dfdl-wg at ogf.org>
>> Date:        15/10/2014 22:05
>> Subject:        [DFDL-WG] do we allow indexing of non-array, non-optional
>> Sent by:        dfdl-wg-bounces at ogf.org
>>  ------------------------------
>>
>>
>>
>> I don't recall whether we decided this matter or not. I would search for
>> it myself, but I tried and failed to find anything. This is a hard topic to
>> do searching on... no good keywords.
>>
>> If element 'e' has maxOccurs = 1, minOccurs = 1 (or neither are
>> mentioned), is e[1] a valid expression? what about e[../some/pathExp/here]?
>>
>> If element 'e' has minOccurs= 0 maxOccurs = 1, is e[1] a valid
>> expression, or do you access an optional element just by ../e ?
>>
>>
>> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
>> *www.tresys.com* <http://www.tresys.com/>
>> Please note: Contributions to the DFDL Workgroup's email discussions are
>> subject to the *OGF Intellectual Property Policy*
>> <http://www.ogf.org/About/abt_policies.php>
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