Re: [wsbpel] Issue - 63 - Support of Array

[Francisco Curbera <curbera@us.ibm.com>]

Hi Ricky,

WSDL 1.1 tried to add some form of array support; the WS-I basic profile
now recommends that you use regular XSD mechanisms for doing this (that is,
use the minOccurs/maxOccurs xsd attributes in your elements.) Seems like a
reasonable solution to me. The alternative of introducing in BPEL  new type
definition mechanisms and also a new ad hoc iterative contruct (I think
that is what you are proposing) seems a bit heavy handed to me.

Regards,

Paco




                                                                                                                                        
                      Ricky Ho                                                                                                          
                      <riho@cisco.com>         To:       wsbpel@lists.oasis-open.org                                                    
                                               cc:                                                                                      
                      09/15/2003 03:47         Subject:  Re: [wsbpel] Issue - 63 - Support of Array                                     
                      PM                                                                                                                
                                                                                                                                        




Ron,

There are two language here.  "the type defintion language", and the
"execution flow language".  BPEL try to focus in the later while rely on
XML Schema to cover the former, which I completely agree.  However, I don't
see XML Schema is supporting "array" since you cannot have repetitive
elements at the root level.

Let me illustrate using a programming language which usually cover both the
"type definition" and "execution flow" portions.  Lets say there is a
user-defined type

class Person {
        String name;
        String[] nickNames;
        int age;
}

Approach 1:
=========
If the programming language supports Array, then you can declare your
variable as ...
Person[] myCustomers;


Approach 2:
=========
However, if the programming language doesn't support Array, then you have
to first define another "type"
class PersonArray {
        Person[] persons;
}
Then you declare your variable
PersonArray myCustomers;


Fortunately, most programming language supports Array so approach 1 is OK.
However, until BPEL supports Array, then we have to go with approach 2
which is more clumsy and tedious.

Best regards,
Ricky

At 08:30 AM 9/15/2003 -0700, Ron Ten-Hove wrote:
      Ricky,

         Is this not just a type definition problem, for which we have XML
      Schema?

         This does touch on another issue -- the lack of the ability to
      build an XML document up through multiple uses of <assign>, which
      would be necessary in your example. This is already on the issues
      list as issue 11.

      -Ron

At 07:35 PM 9/15/2003 +0100, ws-bpel issues list editor wrote:

      This issue has been added to the wsbpel issue list. The issues list
      is posted as a Technical Committee document to the OASIS WSBPEL TC
      pages on a regular basis. The current edition, as a TC document, is
      the most recent document with the title in the "Issues" folder of the
      WSBPEL TC document list - the next posting will include this issue.
      The list editor's working copy, which will normally include an issue
      when it is announced, is available at this constant URL.
      Issue - 63 - Support of Array


      Status: open
      Date added: 15 Sep 2003
      Submitter: Ricky Ho
      Date submitted: 15 September 2003
      Description: Can BPEL declare a variable as a "collection" for a
      particular message type ? For example, if there is a <while> which
      will receive multiple incoming messages into an array variable. How
      does the BPEL look like ?

      I'm not proposing to define a new data type system for BPEL. We
      should leverage what is already in XML schema. Although in the XML
      schema there is a construct to declare repetitive occurrence of
      element structure, it is designed for describing the XML document
      being exchanged ? There is a difference between "there are some
      repetitive elements within a document" and "there are multiple
      documents".

      Therefore, I propose that we need to support "Array"

      For example, if a seller is receiving multiple POMessage from
      multiple buyers, (assuming the complex type of POMessage is already
      defined), the BPEL will look like this ..



      <process>
         <variables>
           <array name="poArray"
      type="POMessage"/>
         </variables>



         <sequence>
           <iterate array="poArray"
      count="10">
             <receive
      partner="buyer" ... array="poArray"/>
           </iterate>
      ....
         </sequence>
      </process>


      Links: Ricky Ho, 13 Sep 2003     Ricky Ho, 13 Sep 2003     Mark
      Little, 15 Sep 2003     Ron Ten-Hove, 15 Sep 2003
      Changes: 15 Sep 2003 - new issue
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