Lets step back and look at why we created ZCML. A primary goal of the component architecture was to make it easier to reuse packages. A major problem with Zope 2 products is that they are hard to customize. The CMF made this a bit better with skins. You could override selected scripts or templates provided by a product by providing overriding versions in your own products or by customizing through the web. You don't have to modify the original product. With the component architecture, you can override at the level of components. As with the CMF, we need to be able to override components without modifying the original package.
The zope.configuration package provides a framework for defining and overriding configurations. It *also* supports an XML syntax. It supports other syntaxes too. (This support may have atrophied somewhat from lack of use. :) In fact, the original syntax for zope.configuration was a simple text-based syntax. The configuration framework is based on computing sequences of actions. When a ZCML file is processed, the individual handlers compute lists of actions. These actions are accumulated as different files are processed. An action includes: - a discriminator used to detect conflicting actions. Two or more actions conflict of they have the same discriminator. An action may have "None" as it's discriminator, in which case, it cannot conflict with another action. - callable, positional, and keyword arguments, - include path used to resolve conflicts. If there is an action in a set of conflicting actions whose include path is a proper prefix of the include paths of all of the other conflicting actions, then the conflict is resolved by keeping this action and discarding the other actions. This is why a file that includes another file can have a directive that overrides directives in the included file. - info that documents the action. - order (lame) that can be used to affect the order in which an action executes. A very high number can be used to make an action execute relatively "last". Configuration processing proceeds in 3 steps: 1. Actions are generated, typically by processing ZCML files. (We'll ignore meta-configuration in this discussion. :) 2. Actions generated in step 1 are analyzed for conflicts. If any conflicts can't be resolved, they are reported as errors. The action info is used in the generation of these errors. 3. Actions are executed by calling their callables with their positional and keyword arguments. The resolution of conflicts in stage 2 is critical for achieving the goal of the configuration framework, which is overriding. The way actions are generated is not critical. (Note that a flaw in this model is that we have no good way to undo actions. We don't need this for normal execution, but it would be very helpful for testing.) Actions need not be generated by executing ZCML. They can be generated by processing configuration files in other formats. They could even be generated by Python code. I'm told that that's what Launchpad does. I'd have no problem with generating actions in Python. It would allow greater control and would probably make action generation much faster. If we did this, We'd probably want to improve the action-generation API. We'd also need to think about how action info should be generated, especially wrt error reporting. Perhaps we should support both ZCML and python action generation. Jim -- Jim Fulton mailto:[EMAIL PROTECTED] Python Powered! CTO (540) 361-1714 http://www.python.org Zope Corporation http://www.zope.com http://www.zope.org _______________________________________________ Zope3-dev mailing list Zope3firstname.lastname@example.org Unsub: http://mail.zope.org/mailman/options/zope3-dev/archive%40mail-archive.com