Re: [sca-bindings] [ISSUE 27] Proposal to Resolve Bindings Issue 27 - "Identifyingdata binding and operation selection"

[Simon Holdsworth <simon_holdsworth@uk.ibm.com>]

Mike,

A couple of comments:

The overall approach looks fine and
agrees with the discussions we have had in the TC.

Two requirements are not explicitly
met by the proposal:

1) Have a different data binding for
specific operations.
In integration scenarios it may be common
to group a set of messages that have different data bindings into a single
interface.

2) Have a separate definition of operation
selection.
In general the way that an operation
is determined from a message can be distinct from the representation of
the message itself - especially where the operation name is derived in
some way from "header" information rather than "body"
information (e.g. deriving the operation from JMS user properties, WMQ
headers, HTTP URL).  In these cases having a separate, single operation
selection identifier

These could be accommodated by the proposal
by having a specific data binding that allows this particular structure.
For example:

<databinding.peroperation>
  <operationselector>?
  <databinding>?
  <operation name=""
nativeName=""?>
    <databinding>
  </operation>*
</databinding.peroperation>

However looking at the JMS binding schema,
that is really what the "operationProperties" element is there
for - originally it had a child element that identified the particular
operation's data binding.  

My preference would be to allow the
operation selector and per-operation data binding explicitly in the standard
binding schema, possibly moving the JMS binding's operationProperties element
up into the SCA binding element.

Regards, Simon

Simon Holdsworth
STSM, SCA Bindings Architect; Master Inventor; OASIS SCA Bindings TC Chair
MP 211, IBM UK Labs, Hursley Park, Winchester SO21 2JN, UK
Tel +44-1962-815059 (Internal 245059) Fax +44-1962-816898
Internet - Simon_Holdsworth@uk.ibm.com

Mike Edwards/UK/IBM@IBMGB

28/07/2008 15:49

To	"OASIS Bindings" <sca-bindings@lists.oasis-open.org>
cc
Subject	[sca-bindings] [ISSUE 27] Proposal to Resolve Bindings Issue 27 - "Identifying data binding and operation selection"

Folks, 

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. 


Proposal: 

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 />?

</binding>

(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">

            <sequence>

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

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

            </sequence>

        <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"/>

    </complexType>


add a Databinding complex type after line 3843:

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

            <sequence>

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

            </sequence>

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

    </complexType>




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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IBM United Kingdom Limited - Registered in England and Wales with number 741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU

---

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU