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Subject: Re: [sca-bindings] [ISSUE 27] Proposal to Resolve Bindings Issue27 - "Identifying data binding and operation selection"

Hi Mike,

From reading through your proposal, this doesn't seem to resolve issue 27 - the problem still exists for JMS and SCA binding until Assembly has approved it, and then we have to update our documents to reflect what they approve.  If, for example, the assembly TC decides that this is beyond the scope of standardization, then we may still wish to use the approach you outline below as defined purely by the bindings TC, perhaps limited to just the JCA specification?

Other than that, the proposal looks like a decent one for the assembly TC to tackle.


Mike Edwards wrote:
OFC0619CC1.0264CDF8-ON80257494.0037D6BF-80257494.005172B7@uk.ibm.com" type="cite">

The following is a proposed resolution of Bindings Issue 27 - "Identifying data binding and operation selection".

Note: This proposal does NOT aim to solve the question of the form of the data binding in the implementation code.
That is a problem for the various SCA language bindings TCs to consider and to solve, since those forms of language
bindings are specific to each language (eg in Java, XML on the wire might be represented in the code as JAXB objects
or as SDOs).

Note that we in the Bindings TC can vote on this resolution, but since it involves changing stuff in the Assembly spec, the
main outcome will be an action item to raise and progress an issue in the Assembly TC  :-(

I leave out the question of defining specific databindings like databinding.xml, databining.jms - I think that we should raise
issues separately for each of these.


In SCA, the form of databindings on the wire (ie the format of the data as carried by a particular transport binding) is defined by
means of a <sca:databinding/> element, which is a child element of the <binding/> element.

There is an abstract <databinding/> element in the sca schema, which any specific databinding extends by means of a
substitution group, to give a particular <databinding.xxx/> element.  This proposal does not attempt to define the details of
any of the specific databindings.  Specific databindings will be defined through separate issues raised against appropriate
Bindings specifications.

A specific databinding may be unique to one SCA binding or it may apply to multiple SCA bindings.

Detailed proposal material follows - unfortunately it will require a set of changes to the SCA Assembly specification, since the
general description of SCA Binding elements is held there.  The following material deals with the specifications at these levels:

1) sca-assembly-1.1-spec-cd01-rev1.doc
2) sca-wsbinding-1.1-spec-WD-03.doc
3) sca-jmsbinding-1.1-spec-WD-03.doc

A) Material for the Assembly Specification

a1) replace the <binding/> element, following each of lines 2646, 2650, 2663, 2667, with the following:

<binding uri="xs:anyURI"? name="xs:NCName"?

                        requires="list of xs:QName"? policySets="list of xs:QName"?/>*

        <databinding />?


(this makes the assumption that policy cannot be applied separately to a databinding - policy is inherited from the containing
binding element)

a2) add, following line 2706

A binding element has the following child elements:

  • databinding (0..1) - a databinding to apply to the data flowing using the binding.  See the databinding section for details.

a3) new Subsection, following line 2733

8.6 Databinding

A databinding is the form that a data structure takes when it is transmitted using some communication binding.  Another way to
describe this is "the form that the data takes on the wire".  A databinding can be specific to a given communication method, or
it may be general, applying to many different communication methods.  An example of a general databinding is XML text format.

Where a particular SCA binding can accommodate transmitting data in more than one format, the configuration of the binding MAY
include a definition of the databinding to use.  This is done using an optional <sca:databinding/> subelement of the <binding/> element.
Where a binding supports more than one databinding, the binding defines one of the databindings to be the default databinding
which applies if no <databinding/> subelement is present.

The base sca:databinding element is abstract and it has no attributes and no child elements.  For a particular databinding, an
extension subtype is defined, using substitution groups, for example:
  • <sca:binding.xml/>
    A databinding that transmits the data as an XML text datastructure
  • <sca:binding.jms/>
    The "default JMS databinding" as described in the JMS Binding specification

Specific databindings can have elements that include either attributes or subelements or both.  
For details about specific databindings, see the related SCA Binding specifications.

a4) Changes/additions to the SCA XML Schemas

Change the definition of the Binding complex type (line 3820) to:

    <complexType name="Binding" abstract="true">


                    <element name="databinding" type="sca:Databinding" minOccurs="0" maxOccurs="1" />

                <element name="operation" type="sca:Operation" minOccurs="0" maxOccurs="unbounded" />


        <attribute name="uri" type="anyURI" use="optional"/>

        <attribute name="name" type="NCName" use="optional"/>

        <attribute name="requires" type="sca:listOfQNames" use="optional"/>

        <attribute name="policySets" type="sca:listOfQNames" use="optional"/>


add a Databinding complex type after line 3843:

    <complexType name="Databinding" abstract="true">


                    <any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded" />


      <anyAttribute namespace="##other" processContents="lax"/>


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

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