[Zope3-dev] what is ZCML?

[Shane Hathaway]

Dieter Maurer wrote:
> Jim Fulton wrote at 2006-3-14 07:23 -0500:
>>- Indirection and abstraction are inherently bad because they
>>  hide things. :)
>>  (This is a corolary of "explicit is better than implicit".)
> 
> 
> I do not agree with this (but I also do not agree with
> "explicit is better tham implicit" -- almost all activities
> would become drastically more difficult if they could only be
> done explicitly: walking, driving, eating, ... I am very happy
> that most things, in real life and in programming work implicitly
> and on an appropriate abstract level).

+1.  When I learn a skill, it is at first completely explicit, and as 
the skill becomes predictable and reliable, it gradually becomes 
implicit.  If I kept everything explicit, I would hinder myself from 
building higher level skills.

So explicit is better than implicit until a sufficiently tight 
abstraction comes about.  Take memory management: yesterday it was 
explicit (malloc/free); today it's mostly implicit (garbage collection). 
Garbage collection is both an abstraction, since programmers no longer 
manage memory directly, and an indirection, since programmers now use 
APIs that call malloc and free.  We all agree GC is good, so explicit is 
definitely not always better than implicit.

To say something is bad only because it's implicit or abstract is a poor 
argument, but to say something is bad because it's a leaky abstraction 
is an argument that can be explored further.  For example, it's not very 
sensible to say implicit acquisition is bad because it's implicit, but 
it is quite sensible to say it's bad because it leaks all attributes and 
forces a lot of code to be aware of wrappers.

Shane