[Zope3-dev] what is ZCML?

[Jeff Shell]

On 3/13/06, Dieter Maurer <dieter at handshake.de> wrote:
> Martijn Faassen wrote at 2006-3-13 17:15 +0100:
> > ...
> >A newer interpretation of ZCML is:
> >
> >"""
> >ZCML is a configuration language that configures a number of basic
> >directives for configuring the component architecture and security:
> >adapters, utilities, security requirements, and little else. Everything
> >else should be done in Python code, as configuration in Python code is
> >more flexible and packages can form a more self-contained whole. ZCML
> >should reflect the underlying universality of the component architecture.
> >
> >If two directives work with, say, adapters underneath, they should
> >really be one directive. ZCML should be simple and minimal so it is easy
> >to grasp.
> >
> >ZCML is not readable standalone. ZCML is simply used to turn on various
> >adapters and such, hooking them into the system, but we do not get a
> >clue what the adapters are doing by just looking at the ZCML - Python
> >code needs to be consulted.
> >"""
> >
> >I believe that this interpretation is the up-and-coming interpretation
> >of ZCML.
>
> I hope not...
>
> Note, that configuration files should be understand and
> adaptable by administrators. Therefore, they should be readable
> and understandable -- without an understanding of the implementation
> (but with reading of the component documentation).

I think differently. ZCML is primarily for programmers. ZConfig style
configuration is what administrators deal with more, isn't it? Maybe
ZConfig and the things in the root $INSTANCE_HOME/etc/ ZCML files.

I don't think of ZCML as administrative configuration.

I'd rather have Python files that I can read and understand what's
going on without having to consult ZCML files, directives,
documentation, and so on, just to understand why a certain class whose
code I'm looking at is getting its behavior when I can see no
superclass. I'd like to know that a class I'm looking at is an adapter
and what it provides and what it adapts without having to dig through
a large ZCML file.

An administrator is not likely to override my 'inplace_editor' view.
He may want to configure global services (if my application is written
that way) such as RDB connection parameters and mail services. But
beyond that, just loading it up in package-includes or in a specific
file is likely to be the bulk of 'administrative' effort.

Did administrators go into your ``initialize(context)`` functions in
your Zope 2 Product's __init__.py files and change things? That's what
I view ZCML as being - a better version of that. (Better in only that
configuration and initialization can be executed separately from
Python imports)

--
Jeff Shell