On Sep 7, 2006, at 6:35 AM, ant elder wrote:
On 9/7/06, Jim Marino <[EMAIL PROTECTED]> wrote:
On Sep 7, 2006, at 2:01 AM, ant elder wrote:
> Great stuff Raymond, some questions and comments inline...
>
> ...ant
>
> On 9/7/06, Raymond Feng <[EMAIL PROTECTED]> wrote:
>>
>> Hi,
>>
>> I finally got the first sample (String<-->DOM) up and running with
>> the
>> databinding framework integrated with the core with some
>> workarounds/hacks.
>> The following is a list of issues and assumptions during the
>> process. I
>> would like to get your opinions so that we can finalize the
>> integration
>> story as soon as possible.
>>
>> 1) Define compatiblity of two service contracts that can be wired
>> together
>> and applicability of databinding transformations.
>>
>> * For local operations that require pass-by-reference semantics,
>> databinding
>> transformation cannot be applied because the source data and
>> transformed
>> result can run out of sync. If the two operations require
different
>> databindings, they are treated as incompatble.
>
>
> This is a bit sad. Couldn't there be some way to say pass-by-value
> is ok,
> something like the opposite of the @AllowsPassByReference
> annotation (and
> consider having this the default)?
>
We should not have pass-by-value as the default for wires between
local services since local services are the default type within a
composite mandated by the SCA spec. The notion of local services as
the default service type was put into the SCA spec to avoid the
mistake made with technologies such as early EJB where everything was
remote. Data transformations should only occur when the target
service contract is remotable. If a target service is remotable,
allows pass-by-ref, and a data transform is required, the resulting
wire will be by-val.
I don't think i'm saying pass-by-value be the default for local
services,
what i'm asking is if operations are possible between local
components using
different data bindings, and if so then it seems more user friendly
that the
default be that it just works without having to define anything
extra to
make it work.
Sure if you can do the data transformation by-value which would be
really difficult to achieve with most databinding frameworks.
Otherwise the wire must be by-ref and the only way to do that is when
the target service contract explicitly declares its remotability.
This is extremely important to be declared in the contract, as
opposed to being the default, since the semantics of the data are
affected and the client cannot treat it as by-ref.
Jim
...ant
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