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From Rahul Akolkar <rahul.akol...@gmail.com>
Subject Re: [scxml] templating/src/xinclude and returning a value(through datamodel/donedata)
Date Thu, 06 May 2010 18:51:53 GMT
On Thu, May 6, 2010 at 2:36 PM, Fabrizio Morbini <fmorbini@gmail.com> wrote:
> Hi Martin, following Rahul advice and explanation the initial problem
> is now solved. However i would like to follow-up on your reply.
> According to the SCXML standard (i.e.
> http://www.w3.org/TR/scxml/#datamodel)
> in particular:
>
> "Logically, there is a single globally visible data model for the
> entire state machine. As an authoring convenience, however, we allow
> <datamodel> as a child of any <state>, thus allowing parts of the data
> model to be distributed throughout the document closer to the
> locations where the data will be accessed. However, all instances of
> the <data> element are created and initialized when the state machine
> is instantiated and may be accessed from any state at any time."
>
> do you mean that the implementation of datamodel in Apache Commons
> SCXML is different from the working draft?
<snip/>

The Commons SCXML implementation is actually more extensible in that
it can support various kinds of datamodel and/or scoping behavior.

The default behavior in v0.9 if you pick up one of the provided
evaluator implementations is different from the single logical
datamodel (it provides a cascading datamodel, much like the block
scopes in procedural languages such as Java). I mentioned in a
previous note how to provide an evaluator that produces a single /
global data model.


> or that the use of src (and
> in the future xinclude?) invalidates the above statement (i.e. one
> single logical datamodel)?.
>
<snap/>

Use of the src attribute of <state> or XInclude is orthogonal to how
datamodel scopes are structured.

-Rahul


> thanks,
> fabrizio.
>
> On Thu, May 6, 2010 at 11:18, Martin Gainty <mgainty@hotmail.com> wrote:
>>
>> Fabrizio-
>>
>> from what ive read in the scxml doc you need to configure the datamodel and their
respective data node children directly under the scm root node e.g.
>> <scxml xmlns="http://www.w3.org/2005/07/scxml"
>>               version="1.0"
>>               initialstate="init-travel-plan">
>>
>>      <datamodel>
>>        <data name="airlineticket">
>> //you can use the Data macro to reference the current value of the requested parameters
e.g.
>> //Commons SCXML defines a Data()
>>   function for use in JEXL or EL expressions, for example:
>>    <var name="arrival" expr="Data(hotelbooking, 'hotel/stay/arrival')" />
>>
>> //   The above expression extracts the arrival date from the hotelbooking
>> //   data in the documents datamodel and stores it in a scratch space variable
>> //   named "arrival". The first argument is value of the name attribute of the
>> //   <data> element and the second is the String value of the XPath
>> //   expression. If more than one matching nodes are found, the first one
>> //   is returned.   //this is different from your current implementation which
uses data elements associated with a state e.g.
>>     <scxml xmlns="http://www.w3.org/2005/07/scxml"
>>               version="1.0"
>>               initialstate="airline-ticket">
>>
>>      <state id="airline-ticket">
>>        <datamodel>
>>          <data...>
>> the association of this data would be to airline-ticket and could not be used in
hotel or restaurant
>> a complete scxml tutorial is available at
>> http://commons.apache.org/scxml/guide/datamodel.html
>>
>> HTH
>> Martin Gainty
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