Furthermore a comonent is not necessarily a composition of objects. In SCA a component is a composition of services. And services as an abstraction work not only for objects but also for procedures, persistent stores, message queues, application functions, etc.
We have to remember and constantly point out that a service is more a design than a technology, a particular way of using technology. I know guys who've created services using COBOL procedures for example.
Eric
----- Original Message ----
From: Anne Thomas Manes <[EMAIL PROTECTED]>
To: [email protected]
Sent: Wednesday, May 24, 2006 7:24:37 AM
Subject: Re: [service-orientated-architecture] Re: MQSeries vs. ESB
Are you saying that you disagree that EJB defines a model for constructing and packaging components that run in an EJB container? Or are you disagreeing the EJB is a component model?
Every component model I've ever seen is platform-specific, and it defines a container-oriented packaging scheme.
Service orientation is platform-agnostic. Although developers often implement service using components, it's by no means a requirement. You can implement services using EJBs and generate a JAX-WS interface around the beans. But I think it's overkill. When using Java, I recommend using POJOs. (Do you consider POJO to be a component model? If so, what's the difference between "object" and "component"?) But more to the point, you can also implement services using Python or Perl or Ruby or whatever and expose them using POX over HTTP. No component model involved there -- but it's certainly service-oriented.
Anne
----- Original Message ----
From: Anne Thomas Manes <[EMAIL PROTECTED]>
To: [email protected]
Sent: Wednesday, May 24, 2006 7:24:37 AM
Subject: Re: [service-orientated-architecture] Re: MQSeries vs. ESB
Are you saying that you disagree that EJB defines a model for constructing and packaging components that run in an EJB container? Or are you disagreeing the EJB is a component model?
Every component model I've ever seen is platform-specific, and it defines a container-oriented packaging scheme.
Service orientation is platform-agnostic. Although developers often implement service using components, it's by no means a requirement. You can implement services using EJBs and generate a JAX-WS interface around the beans. But I think it's overkill. When using Java, I recommend using POJOs. (Do you consider POJO to be a component model? If so, what's the difference between "object" and "component"?) But more to the point, you can also implement services using Python or Perl or Ruby or whatever and expose them using POX over HTTP. No component model involved there -- but it's certainly service-oriented.
Anne
On 5/23/06, Jerry Zhu <[EMAIL PROTECTED]> wrote:
--- Anne Thomas Manes <[EMAIL PROTECTED]> wrote:
> Components are typically associated with a component
> model -- JavaBeans, EJBs, servlets, COM, ActiveX,
CORBA Component Model, etc. And now, most
> recently, Service Component Architecture (SCA). In
> all cases, these component models define
implementation-specific packaging schemes.
>
> Services are more abstract and
implementation-neutral.
Anne, I disagree with you here.
Objects, Components and Services belong to three
different kinds of technologies and all are models.
An object groups data and functions into an unity of
levels of access. A component groups objects into a
unity of interaces of access. A service groups
components into an unity of components. I see this
evolotion of technology as stages of integration into
greater capabilities. Each time of intergation the
unity increases its capability and solves different
types of problems. The implementation of all three
unities requires platforms. Platforms are languages.
The use of unities of a technology in the SW does not
qaulify the SW having an architecture of that
technology. It must use the unities in certain way
such as object oritented SW must use inheritance. I
cannot see that SW without inheritance is object
oriented. I call this unity composing patterns. Each
technology has its composing patterns. Hence to judge
whether a SW is using Service technology is to see
that both services and service composing patterns are
used. Service unity is clear and the composing
pattern are to be defined.
Jerry
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