Stephen McConnell wrote:
> 
> Carsten Ziegeler wrote:
> 
> > Stephen McConnell wrote:
> > 
> >> From the front page:
> >>
> >>   The Avalon Meta Model defines the functional structure
> >>   of component types and services. A Type definition
> >>   contains information about deployment and runtime
> >>   dependencies together with information about the
> >>   services that a component type can provide.
> >>
> >>The following page describes the XML schema used to define a Type 
> >>instance - http://avalon.apache.org/meta/meta/info/type/index.html
> >>This is paralleled in the API documentation for the immutable Type 
> >>class (org.apache.avalon.meta.info.Type).  Keep in mind 
> that the Type 
> >>is simply an immutable class that exposes all of the descriptive 
> >>features of a component (that's it).
> >>
> > 
> > Ok. So by defining a type I don't "create" a component, which means
> > if I only define a type, I can't lookup up something?
> 
> Not directly.
> 
> A Type is a description of a component implementation.  
Ok, yes sorry that was my latest understanding as well :) Ok, so type
as a term makes sense.
Perhaps the docs should simply contain your sentence above as
the first sentence, so readers immediately see what a type is
before they read the longer and more detailed version.

> Based on 
> information accessible from an instance of Type you know all 
> about the 
> structural and runtime dependencies that a instance of a 
> corresponding 
> component class will require.
> 
Ok.

> > Now, we could argue about the correct terms for months but the
> > term "type" is imho misleading here. If a type exposes all
> > features of a component why is it called a type and not
> > component?
> 
> What is a component?
> 
> Here is my view.
> 
> A component is a reusable computation unit that provides zero or more 
> functional services.  
Agreed.

> This implies that a component is more 
> than a class 
> or collection of classes.  It is computational unit that can 
> be deployed 
> predictably in different application scenarios and environments.
Yes.

> 
> To achieve this you can break down "component" into:
> 
>    * a component *type* description
Containing the provided services.

>    * an *implementation* of the type
>    * a deployment *profile*
> 
> Collectively these different aspect are brought together by a 
> container 
> through the process of "instantiating a component".
> 
Ok, now I'm on track :) I will post my other questions about meta
soon :)

Many thanks!

Carsten


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