control flow in tuscany

[Haibo Zhao <zh...@cs.uga.edu>]

Hi all,

      I am a newbie to Apache Tuscany. I come to Tuscany for two reasons:

     (1) Tuscany is very easy to use and extremely flexible (I have
been working with BPEL based service composition for 4 years, it was
so much pain....)

     (2) I am applying for a Tuscany related project in "Google summer
of code" (Adding Gdata bindingg into Tuscany)

     The question I am asking is not really related to the two reasons
above, but about how the control flow is handled in Tuscany at the
implementation level.

     I read the references and wiring/autowiring part in the Assembly
Model Specification and tried a few samples and simple examples. My
understanding is that the service components are wired together by so
called "wires", which is obviously enough for the case that the
composition is a simple sequence of service components, but how about
more complicated control structures like conditions and even loops.

     My question is "how complicated control structures like
conditions, loops can be supported/implemented by Tuscany?" Or I am
missing the point here?


     Thanks,
      Haibo

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Re: control flow in tuscany

[Simon Laws <si...@googlemail.com>]

On Mon, Apr 7, 2008 at 11:31 PM, Haibo Zhao <zh...@cs.uga.edu> wrote:

> Hi all,
>
>      I am a newbie to Apache Tuscany. I come to Tuscany for two reasons:
>
>     (1) Tuscany is very easy to use and extremely flexible (I have
> been working with BPEL based service composition for 4 years, it was
> so much pain....)
>
>     (2) I am applying for a Tuscany related project in "Google summer
> of code" (Adding Gdata bindingg into Tuscany)
>
>     The question I am asking is not really related to the two reasons
> above, but about how the control flow is handled in Tuscany at the
> implementation level.
>
>     I read the references and wiring/autowiring part in the Assembly
> Model Specification and tried a few samples and simple examples. My
> understanding is that the service components are wired together by so
> called "wires", which is obviously enough for the case that the
> composition is a simple sequence of service components, but how about
> more complicated control structures like conditions and even loops.
>
>     My question is "how complicated control structures like
> conditions, loops can be supported/implemented by Tuscany?" Or I am
> missing the point here?
>
>
>     Thanks,
>      Haibo
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tuscany-dev-unsubscribe@ws.apache.org
> For additional commands, e-mail: tuscany-dev-help@ws.apache.org
>
>
Hi Haibo, welcome to Tuscany.

SCA allows you to describe how one component is connected to another
component by wiring component references to component services. It doesn't
however allow you to control to the flow of messages along these wires. All
of the business logic in SCA is contained within component implementations.
This is where decisions will be made about when and where messages will
flow.

An analogy for this an electronic circuit board. The chips on the circuit
board do the processing while the copper tracks simply transfer the messages
from one chip to another.  We wouldn't expect the copper wires  to perform
complex message processing. If we need that to happen we just put another
chip in. And so it is with SCA. Components are wired together and if you
need to make routing decisions between components then put another component
in to do it.

Does that help?

Regards

Simon

In Tuscany Java SCA you can implement a component using many different
techniques from say a simple Java program right through to a complex BPEL
flow. =