NEW ISSUE: Difficulty using source= attribute to pull values into complextypes

[Mike Edwards <mike_edwards@uk.ibm.com>]

Folks,

Matthew Peters originally raised this
issue on the OSOA Assembly mailing list, but I think that it is worthy
of consideration
within the OASIS Assembly TC, so I am
raising it formally as an issue.


Yours,  Mike.

Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
Email:  mike_edwards@uk.ibm.com


I have a property which is a complex
type, and I wanted to use source= attribute to pull the values down from
a global property within my .composite. This turned out to be not quite
as easy as I thought. I have been through several options. 

_________________________
My first idea, which was wrong


I have a composite containing several
different components. I want to specify some proerties at a global level.
One of the components wants to use a omplex type for one of the properties.
The complex type is already defined elsewhere. For this example I'll simplify
it so it has two elements, which are long and short titles that the component
will use: 

<complexType name="titles-type">

  <sequence>

    <element name="long-title"
type="xs:string"/> 
    <element name="short-title"
type="xs:string"/> 
  </sequence>
</complexType>


I want to define some global properties
in my composite, with values which will be pulled down into this and other
components. But the structure of the globals, and the names of the elements
are not the same as the component's and I don't want them to be the same
- I don't want the structure of the global properties forced on me by the
structure of the property for the one component. Here's the global property
where just two of the elements are the titles I want:


<property name="global-properties"
type="app-namespace:global-properties-type">    
 
    <application-full-name>Whizzo
Insurance, a subsidiary of Fizzo</application-full-name>

    <application-short-name>Whizzo
Insurance</application-short-name> 
  . <!-- and lots of other elements
in here as well --> 
</property>


Here's what I really wanted to write
in the component before I was thinking clearly. I imagined that I was going
to use source= but hadn't realised that I was about to put the source=
on the wrong elements:

<component ...

   <implementation....../>

   <property name="app-titles"
type="titles-type" 
      <app-titles
xsi:type="titles-type">  
         <long-title
source="global-properties/application-full-name"/>  
         <short-title
source="global-properties/application-short-name"/>

      </my-app-complex-element>

   </property>

</component>

    
The mistake I made here of course is
that source= means something to sca on a property element, but where I
wanted to put it was on an element that is part of a complex type that
is nothing to do with sca. And I don't control the complex type myself
so I can't add to the schema to allow it to take an sca:source= attribute.


___________ 
Two options 

******Option 1.  
I can give up using the info-type complex
type altogether and flatten all the elements out into separate properties
and write e.g.
<property name="long-title"
source="global-properties/application-full-name"/>  
<property name="short-title"
source="global-properties/application-short-name"/>

A bit of a shame, but I can do that


******Option 2.

I can copy the complex type for app-titles-type
and add a source= attribute, allowing me to write more or less what I proposed
the first time. But this is a bit weird - I am taking the SCA idea of source=<XPath
expression> but at runtime someone is actually going to have to make
it happen and I guess it will be up to the implementation to do it for
me somehow. I can't expect it to just happen. 

_______________

What I really want
is for SCA to have a more powerful
mapping system to allow me to do more than source= on scalar properties.
Or some other magic. 

I don't think I will be the only one
to run into this. Any suggestions? 
Matthew Peters

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