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


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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