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Re: invalid binding expression error

From: John Boyer <boyerj@ca.ibm.com>
Date: Tue, 14 Sep 2010 08:57:31 -0700
To: e-letter <inpost@gmail.com>
Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, www-forms@w3.org
Message-ID: <OFA7D19FEE.CED1C62C-ON8825779E.0056B6B0-8825779E.0057AA31@ca.ibm.com>
Hi everyone,

Use of the term "document element" comes right from the XML spec itself. 
The document element is the root element of the XML document, the one 
matched by BNF rule #1 in the XML specification [1]

[1] http://www.w3.org/TR/REC-xml/#sec-well-formed

Definition 2 in [1] says "There is exactly one element, called the root, 
or *document element*, ..."

Note that the XForms spec may be a bit difficult to use to learn XForms, 
as it is first and foremost a specification for XForms processor 
developers.

That being said, helpful information on the context node for evaluating 
XPath expressions appears in Section 7 of XForms 1.1, and most notably in 
Sections 7.2 [2] and 7.4 [3].

[2] http://www.w3.org/TR/xforms11/#expr-eval
[3] http://www.w3.org/TR/xforms11/#expr-expression-categories

Best regards,
John Boyer




From:
e-letter <inpost@gmail.com>
To:
"C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>
Cc:
www-forms@w3.org
Date:
09/13/2010 11:50 PM
Subject:
Re: invalid binding expression error



On 13/09/2010, C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com> wrote:
> Comments interspersed.
>
> On 13 Sep 2010, at 14:55 , e-letter wrote:
>
>> On 12/09/2010, C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
>> wrote:
>>>
>>> On 12 Sep 2010, at 10:54 , e-letter wrote:
>>>
>>>> On 12/09/2010, C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
>>>> wrote:
>>>>
>>>>> You might try rephrasing the nodeset value to "/purpose/analysis/
>>>>> @type"
>>>>> or "analysis/@type" (if that is what you actually intend) and see
>>>>> if
>>>>> that helps at all.
>>>>>
>>>> The latter worked thank you, but I wanted the user to see the values
>>>> (i.e. epc england, epc scotland), not the attributes.
>>>
>>> That's a straightforward change to the XPath expression:
>>> /purpose/analysis/@type points to the attribute, and to
>>> point to the analysis element you want /purpose/analysis
>>> or (given that /purpose is the document element and thus
>>> in this case the context node) just "analysis".
>>>
>> Again, the latter suggestion works, thank you, but in truth I don't
>> understand this reference to the 'document element'.
>
> In an XML document, the 'document element' is just the
> outermost element of the document, the one within which all
> the other elements appear.  Sometimes it's called the root
> element.  The XPath spec uses the term without explanation, as
> it's fairly standard XML terminology.
>
Yes, I understood root element as I had seen reference to that term,
but never 'document element'.

>> Could you point
>> to a relevant part of the specification that explains 'context node'
>> please?
>
> I don't see any full explanation of the idea of context node
> in the XPath 1.0 or 1.1 spec -- it's not an XForms-specific
> idea.
>
> The 'context node' is the node in a document which serves
> as the reference point for evaluating any context-dependent
> parts of an XPath expression.  The idea is an important part
> of XPath, and in order to provide an effective rule for
> interpreting the XPath expressions in a form, the XForms
> spec must specify how to determine the context node used
> for the interpretation of any given expression.  That task is
> performed by section 7.4 of the XPath 1.0 spec, 7.2 of the
> 1.1 spec.
>
> If the concept is unfamiliar to you, you may find it helpful
> to read some introductory tutorials on XPath.
>
>>
>>
>> I looked at the output file 'testsubmit.xml' which appears as:
>>
>> <?xml version="1.0"?>
>> <generalinformation>
>>                               <generalinformation/>
>>               </generalinformation>
>
> I think this means you got the submit to work.  Good!
>
>> This seems wrong to me; I was expecting the output to contain 'epc
>> england' if chosen from the list menu. Am I right to conclude that
>> this is a bug with writer?
>
> Probably not, as far as I can tell from the evidence I've
> got.  Your submission element is a child of the second of
> your two model elements, so what it submits (in the absence
> of any instructions to the contrary) is the default instance
> in that model, which has the shape you record above (a
> generalinformation element containing another generalinformation
> element).  The string 'epc england' is content in the default
> instance of your *first* model, for which your form does not
> currently define any submission.
>
> I wonder if a simpler form might be easier to get started with?
>
This concept of using two model elements originates from a writer
tutorial, advising to populate a list menu with elements from a second
model. Now I have discovered how to manipulate the writer content.xml
file without the writer user interface I will simplify the form with a
single model. Thank you!

> HTH
>
> Michael Sperberg-McQueen
>
> --
> ****************************************************************
> * C. M. Sperberg-McQueen, Black Mesa Technologies LLC
> * http://www.blackmesatech.com
> * http://cmsmcq.com/mib
> * http://balisage.net
> ****************************************************************
>
>
>
>
>
Received on Tuesday, 14 September 2010 15:58:28 GMT

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