[Zope3-dev] what is ZCML?

[Jean-Marc Orliaguet]

Jim Fulton wrote:

> Jean-Marc Orliaguet wrote:
>
>>
>>>
>>>
>>> I was refering to high-level ZCML, such browser:page, browser:menu, etc
>>> vs low-level directives like adapter.
>>>
>>> Jim
>>>
>>
>> I would say that they paraphrase more lines of code than the 
>> low-level ones, but they fundamentally add no extremely valuable 
>> abstraction since a page is an alias for a multiadapter, a menu 
>> registers utilities, interfaces, ..
>
>
> Wrong.  the page directive defines a class and combines multiple
> configurations.  This is definately a higher level of abstraction.
>
>

OK, but that's not "violent" abstraction. For a python programming, 
going to ZCML does feel like "wow, I can do some high-level 
configuration of my application", we are still configuring fairly 
low-level components (pages, menus, views ...), they still need to be 
configured on a higher level for the application to start working. The 
effort is not necessarily justified compared with how views for instance 
are declared inline with the code. By looking at 
zope/app/publisher/browser/viewmeta.py it is clear that most of the code 
is there handle all the different page registration options (templates, 
attributes, security, ..).

the fact that the "abstraction" done in ZCML does not succeed in hiding 
information is an issue, IMO this is because the directives in ZCML 
correspond to low-level objects and the objects' internal way of 
functioning is getting too much exposed  (not enough encapsulation) as 
its the case with browser:page. 

/JM