Re: [wsbpel] Issue 11 - Call for Discussion

[Alex Yiu <alex.yiu@oracle.com>]

Hi, Danny and all others,


Here is our take on issue 11 so far (after consulting with some internal and external people).
I hope you would find the points below make senses.
(In short, I am for Danny's changes with some minor modification and clarification)


Thanks!

Regards,
Alex Yiu


===========================

BPEL Issue 11

Whether to add:

We feel comfortable of adding some extra basic XML manipulation operations to BPEL, as long as we do not run into a slippery slope business and BPEL TC members understand and agree that BPEL is NOT targeted as a full blown XML manipulation and / or transformation language. The reasons that we feel it is OK to add those basic operations:

• XQuery and XPath are side-effect-free languages. XQuery does NOT modify existing XML data. It will only construct a new piece of document.
  
• The new W3C XUpdate WG is kind of in its bootstrapping mode now. It will take at least a year or two for it to become stable for BPEL vendors to use.
  
• Without any BPEL side-effect-ful assign-like constructs, we cannot even do some the simplest XML data modification. For simple XML data modification, it may be an overkill to ask BPEL developers to cross the language boundary to use another programming language.
  

We can and should restraint ourselves by emulating structure modification semantics supported by W3C DOM API. There are ONLY 4 API:

• replaceChild (already done in assign/copy),
  
• appendChild
  
• insertBefore
• removeChild

insertAfter functionality can be done by appendChild and insertBefore. E.g.:
insertAfter into "/po/item[$index]" can be done by insertBefore into "/po/item[$index+1]" or appendChild.

How to add:

We agree Danny's proposal in general. We would suggest to add some minor modification and some clarification it.

(1)  appendChild:

<assign>
  <appendChild>
     <from variable="..." part="..."? query="..."? /> 
         <!-- restricted version of from-spec -->
     <to variable="..." part="..."? query="..."? />   
         <!-- restricted version of to-spec -->
         <!-- no child integer index supported -->
  </appendChild>
</assign>

(Question: With child integer index, will appendChild make look like insertAfter? So, do we  want to drop it?)

(2) insertBefore:

<assign>
  <insertBefore>
     <from variable="..." part="..."? query="..."? /> 
         <!-- restricted version of from-spec -->
     <to variable="..." part="..."? query="..."? />   
         <!-- restricted version of to-spec -->
  </insertBefore>
</assign>


(3) remove:

<remove>
     <from variable="..." part="..."? query="..."? /> 
         <!-- restricted version of from-spec -->
</remove>

(Question: do we want to support remove a message part? I guess not. )

Note:

• We may want to reuse the syntax of from-spec and to-spec by restricting it. Then, it is easier for BPEL users to learn and for BPEL vendor to do code reuse.
  
• For from-spec, we would use variable version of from-spec only (as Danny suggested in the email)
• For to-spec used in appendChild and insertBefore, we would use variable version of to-spec only.
  
• We can also have altenative syntax for merging insertBefore and appendChild to <copy>. e.g.:
• <copy operation="replace">
• <copy operation="insertBefore">
• <copy operation="appendChild">
  

===========================



Danny van der Rijn wrote:

select is the same as query.  it should probably be renamed query, but was
left over from the last round of discussions.

danny

----- Original Message ----- 
From: "Edwin Khodabakchian" <edwink@collaxa.com>
To: "'Danny van der Rijn'" <dannyv@tibco.com>; "'Wsbpel@Lists. Oasis-Open.
Org (E-mail)'" <wsbpel@lists.oasis-open.org>
Sent: Monday, February 23, 2004 3:29 PM
Subject: RE: [wsbpel] Issue 11 - Call for Discussion


  

Hi Danny,

Could you please clarify how the select attribute would work when the to
variable is a message? Is this intentional or do you use select as a
placeholder for part/query?

Thank you for the clarification,

Edwin

-----Original Message-----
From: Danny van der Rijn [mailto:dannyv@tibco.com]
Sent: Monday, February 23, 2004 10:29 AM
To: 'Wsbpel@Lists. Oasis-Open. Org (E-mail)'
Subject: [wsbpel] Issue 11 - Call for Discussion

maybe people are as tired of discussing issue 11 as I am, but if it stays
this quiet, I may just have to put up a proposal for vote.  Here's the
current proposal, which includes additions inspired by Glenn Mi.


under the <assign> element, there will be 6 possible
elements, where now there is only 1.

<copy>
  <from/>
  <to/>
</copy>
as current.
-----------------------------
<insertBefore>
  <from/>
  <to select="XPath Expression evaluates to one node"/>
</insertBefore>

creates a sibling before the select expression
-----------------------------
<insertAfter>
  <from/>
  <to select="XPath Expression evaluates to one node"/>
</insertAfter>

creates a sibling after the select expression
-----------------------------
<append>
  <from/>
  <to select="XPath Expression evaluates to one node"
        child="integer XPath expression"? />
<append>

creates a child of select expression at the child-th position.  child
defaults to last().
-----------------------------
<remove select="XPath expression evaluates to one node"?>

removes a node

----- Original Message ----- 
From: "Danny van der Rijn" <dannyv@tibco.com>
To: "'Wsbpel@Lists. Oasis-Open. Org (E-mail)'"
    

<wsbpel@lists.oasis-open.org>
  

Sent: Wednesday, February 18, 2004 5:10 PM
Subject: Re: [wsbpel] Issue 11 - It's Baaaack


    

----- Original Message ----- 
From: "Glenn Mi" <gmi@collaxa.com>
To: "Danny van der Rijn" <dannyv@tibco.com>; "'Wsbpel@Lists. Oasis-Open.
      

Org
    

(E-mail)'" <wsbpel@lists.oasis-open.org>
Sent: Wednesday, February 18, 2004 4:54 PM
Subject: RE: [wsbpel] Issue 11 - It's Baaaack


      

Danny:

I start to like your proposal more now. Two points I want to add:

1) In your <to> construct, it seems that we can just use
one of

<to variable="ncname" property="qname"/> and
<to variable="ncname" part="ncname"? query="queryString"?/>

Or does your select="XPath Expression evaluates to one node"
actually mean the normal to-spec construct ?
        

yes.  the normal to-spec, but restricted to variables, and their parts.
i.e. not partnerlinks, etc.  in the spec, this is the "first" form of
      

the
  

to-spec referred to in 9.3, and extended for executable processes in
      

14.3
  

2) And there are cases to insert and remove part of a message variable
(varable defined as <variable name="abc" messageType="ns:xyz"/>). In
        

those
    

cases you don't need query string and you don't care about the order.
So it make sense to have something like:

<insert>
<from .../>
<to variable="abc" part="def"/>
</insert>
        

unless i'm mistaken, <copy> can be used here.

      

and

<remove variable="abc" part="def"/>.
        

you are correct.  this should be added.  i believe that this is the only
      

one
    

of the new 4, though, that should have "select" be optional.


      

Glenn

-----Original Message-----
From: Danny van der Rijn [mailto:dannyv@tibco.com]
Sent: Wednesday, February 18, 2004 3:19 PM
To: 'Wsbpel@Lists. Oasis-Open. Org (E-mail)'
Subject: Re: [wsbpel] Issue 11 - It's Baaaack


to preempt the pedantic among us, there's a copy/paste error in the
proposal.  it should read:
"under the <assign> element, there will be 5 possible elements, where
        

now
    

there is only 1."

----- Original Message -----
From: "Danny van der Rijn" <dannyv@tibco.com>
To: "'Wsbpel@Lists. Oasis-Open. Org (E-mail)'"
        

<wsbpel@lists.oasis-open.org>
      

Sent: Wednesday, February 18, 2004 3:16 PM
Subject: [wsbpel] Issue 11 - It's Baaaack


        

during today's conference call, we took a straw poll, where
          

approximately
      

2/3 voted to attempt to resolve issue 11.  (i'll leave the exact
          

count
  

to
      

the minutes).  i would like to resurrect a large part of my previous
proposal (i'll drop "rename").  to me, this is a viable proposal,
          

and
  

i
    

would be satisifed if it ended up being adopted into the spec.
          

however,
    

maybe in the months since we last thought about it, someone else has
          

a
  

reasonable alternative.

danny

My proposal:  under the <assign> element, there will be 6 possible
elements, where now there is only 1.

<copy>
  <from/>
  <to/>
</copy>
as current.
-----------------------------
<insertBefore>
  <from/>
  <to select="XPath Expression evaluates to one node"/>
</insertBefore>

creates a sibling before the select expression
-----------------------------
<insertAfter>
  <from/>
  <to select="XPath Expression evaluates to one node"/>
</insertAfter>

creates a sibling after the select expression
-----------------------------
<append>
  <from/>
  <to select="XPath Expression evaluates to one node"
        child="integer XPath expression"? />
<append>

creates a child of select expression at the child-th position.
          

child
  

defaults to last().
-----------------------------
<remove select="XPath expression evaluates to one node">

removes a node


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