[wsbpel] Issue 157 - XSLT and copy/replace semantics

[Charlton Barreto <cbarreto@adobe.com>]

Hi all,

Below is a proposal which pulls together several ideas on using XSLT  
to perform <copy> - thanks to Alex, Ron and Ugo for the input they  
provided into this.

> On reviewing this issue I would like to propose that we adopt the  
> use of XSLT functionality to perform <copy>. This would involve  
> using said XSLT functionality in <from>. Note that this is  
> different from my understanding of Assaf and Yuzo's original  
> proposal/thoughts which would use this functionality in <to>.
>
> By using XSLT functionality in the <copy> from-spec, we accomplish  
> the economy of defining the copy/replace semantics which is  
> generating the greatest churn with respect to fully defining the  
> current copy concept. This XSLT functionality provides a rich set  
> of copy/replace semantics which in this context can be used to  
> achieve the same results as the current copy concept while  
> addressing the lingering questions in the current concept and  
> providing semantic simplification. At the same time, current copy  
> functionality is maintained.
>
> The idea is that we essentially replace the original source tree  
> with the new tree created by the XSLT transform. This covers both  
> copy/replace as follows:
> 1) The result is semantically a new tree, where the original source  
> tree distinctly existed.
> 2) The result tree is semantically a modification of the original  
> source tree, where the result tree replaces the original.
>
> This achieves the same as the current copy concept, but delegating  
> the responsibility to XSLT functionality. To use this, we would  
> have to assign a stylesheet to the from-spec in order to associate  
> it with the copy/replace.
>
> To illustrate, let's take Yuzo and Ugo's example:
>
> var1:
> <invoice test="false">
>         <invoiceNumber>9876</invoiceNumber>
>         <orderNumber>0000</orderNumber>
>         <amount/>
>         <billingAddress><street/></billingAddress>
> </invoice>
>
> Lets assume we wish to modify this variable as follows:
>
> <invoice test="false">
>         <invoiceNumber>9876</invoiceNumber>
>         <orderNumber>1234</orderNumber>
>         <amount/>
>         <billingAddress><street>1
> Somewhere</street><state>SW</state></billingAddress>
> </invoice>
>
> We would use XSLT as follows:
>
> Stylesheet:
> <xsl:stylesheet version="1.0"
>     xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
>
>     <xsl:template match="orderNumber">
>         <xsl:element name="orderNumber">
>             <xsl:value-of select="1234"/>
>         </xsl:element>
>     </xsl:template>
>
>     <xsl:template match="billingAddress">
>         <xsl:element name="billingAddress">
>             <xsl:copy-of select= ... node corresponding to
> "<billingAddress><street>1
> Somewhere</street><state>SW</state></billingAddress>" ... />
>         </xsl:element>
>     </xsl:template>
>
>     <xsl:template match="@*|node()">
>         <xsl:copy>
>             <xsl:apply-templates select="@*|node()"/>
>         </xsl:copy>
>
>     </xsl:template>
>
> </xsl:stylesheet>
>
> Applying the XSLT transform to the tree contained in var1 (i.e.  
> tree1) to produce tree2, we would then replace the contents of var1  
> with tree2 This achieves XSLT-based copy - var1's contents are the  
> same as if we had used the copy operations based on the current  
> concept. This achieves the same copy/replace semantics of the  
> current concept without violating XSLT semantics of XSLT  
> transformations (i.e. no modification of tree1). This is how the  
> source tree is "modified" while generating a distinct result tree.

Please provide any feedback you may have on this.

Cheers,

-Charlton.

Charlton Barreto
P 1.408.536.4496
cbarreto@adobe.com
www.adobe.com