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From Jaroslav Pullmann <jaroslav.pullm...@fit.fraunhofer.de>
Subject Re: [SCXML] Help with Data()
Date Thu, 11 Dec 2008 10:40:19 GMT

  Dear Rahul,

   your quick response and dedication to the project are very appreciated!

  Suprisingly the last WD does not contain the assign/@src anymore.
  I hope this decision will be revised to preserve a standard means
  to access remote data and assign it to the (static) data model.

  Your proposal to interpret assign/@src as an expression follows
  the way how e.g. send/@target is treated. This shortcut syntax
  (ommiting @srcexpr) would be fine, when consistent and intuitive
  throughout the spec. Such, exceptions like invoke/@srcexpr should
  be removed. Could you please address this question within the
  working group ?

   Best regards
     Jaroslav


Rahul Akolkar wrote:
> On Wed, Dec 10, 2008 at 10:38 AM, Jaroslav Pullmann
> <jaroslav.pullmann@fit.fraunhofer.de> wrote:
>>  Dear all,
>>
>>  could you please give me a short hint on these questions ?
>>
>>  1) where to find documentation and source code for the "Data"-function for
>> JEXL evaluator ?
>>     I need to clarify which subset of XPath is supported.
>>
> <snip/>
> 
> There is some documentation of this page (towards the bottom):
> 
>   http://commons.apache.org/scxml/guide/datamodel.html
> 
> Source is here, for example (trunk version):
> 
>   http://commons.apache.org/scxml/xref/org/apache/commons/scxml/Builtin.html
> 
> 
>>  2) there is no "name" attribute on <data> in current working draft, but
>> Data() depends on it:
>>
>>
>>      a) <data ID="foo"><foo>bar</foo></data>
>>      b) <data name="foo"><foo>bar</foo></data>
>>
>>    the action <log expr="Data(foo,'node()')"/>
>>
>>    - throws an error for a: Data(): Cannot evaluate an XPath expression in
>> the absence of a context Node
>>    - returns "bar" for b)
>>
>>   Will the Data() implementation be adapted to the spec ?
>>
> <snap/>
> 
> In this case, it happens to be the other way around :-)
> 
> The casing of the ID attribute (all uppercase) in the draft was
> unfortunate, and this has been discussed (and in all likelihood will
> change to lowercase in the next draft). So, please use lowercase i.e.
> 
>   <data id="foo"><foo>bar</foo></data>
> 
> 
>>  3) How to address nodes in a specific namespace via Data() ?
>>
>>      <data name="foo"><f:foo xmlns:f="fooNS"><baz>bar</baz></f:foo></data>
>>      <!-- how to address f:foo ? -->
>>      <log expr="Data(foo,'foo')"/>
>>
> <snip/>
> 
> I'm running out of time for email, so let me point to a fairly
> comprehensive test case SCXML document that demonstrates use of
> namespace prefixes in XPath expressions (the bottom line is prefixes
> in an expression are resolved based on the enclosing namespace
> declarations at the location where the expression occurs in the
> document -- and so these prefixes may be different from the prefixes
> specified in the <data>). Here is the test document (long URL, may get
> fragmented):
> 
>   http://svn.apache.org/repos/asf/commons/proper/scxml/trunk/src/test/java/org/apache/commons/scxml/env/jexl/datamodel-03.xml
> 
> Please feel free to bring up anything that isn't clear after going
> through that test document.
> 
> 
>>  4) assign supports static source-URLs via @src. Is there a way to supply an
>> srcexpr,
>>  or what would be the recommended way to perform and store XML data from
>> parametrized GET-requests ?
>>
>>  broken example:
>>
>>    <data ID="MyId">3q495</data>
>>    <assign location="Data(test,'response')" expr="
>> 'http://localhost:8080/exist/ess/queries/getData.xqy?id=' + MyId "/>
>>
> <snap/>
> 
> I think the src attribute value should be evaluated as an expression
> (that way, there isn't any need for another srcexpr attribute and
> static URLs / string attribute values can be surrounded by single
> quotes if needed). This will cover usecases as illustrated by your
> example above.
> 
> Please open an enhancement request in JIRA [1] so we remember this, thanks.
> 
> -Rahul
> 
> [1] http://commons.apache.org/scxml/issue-tracking.html
> 
> 
>>  Many thanks !
>>   Jaro
>>
>>
> 
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-- 
Jaroslav Pullmann
Web Compliance Center - Fraunhofer FIT
Schloss Birlinghoven, D-53757 Sankt Augustin, Germany
Phone: +49-2241-142623    Fax: +49-2241-142065

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