On Jun 25, 2005, at 11:50 AM, Phillip J. Eby wrote:
At 08:55 AM 6/25/2005 -0700, Andi Vajda wrote:
Defining these well known entry points means to:
- define an addressing scheme (ref collection based paths is my
proposal)
- define a schema that contains all these commonly used
collections (all
web servers as per your example above)
Currently, the Chandler application schema is in flux, the
ItemCollection/Query stuff is being redone and the 'addressing'
issue is not settled. Once it is, we can define well known
addresses to repository entry points containing collections of
items of interest.
Until then, using KindQuery is the usual starting point but I do
hope that once these issues are fixed, we use it only as last resort.
I don't see any actual conflict here; what stops you from simply
maintaining kind-extent sets internally as part of this new
addressing paradigm? Do you intend not to support intentional sets
at all, only extensional ones? Because if so, I think that's going
in a bad direction for developer comprehension and usability. This
is one of ZODB's bigger flaws: it has no inherent mechanism for
efficient queries, but you instead have to reify sets as navigation
extents, such as via ZCatalog.
The goal is definitely to support intensional sets. I have support
fort Kind extents in the set paradigm, and one goal for the
addressing scheme is to provide a way to name these. I think that
the KindExtents are going to be the entry points for third party
parcels. Otherwise they will have to know about refcollections
defined by other parcels in the system or we will have to implement
some kind of naming registry, which is something I'd like to avoid.
In Andi's example, an application that wants to deal with web servers
not only needs to know about the WebServer kind, it needs to know the
name of the item which owns the ref collection, and the name of that
attribute. If the parcel that defines that item suddenly changes it,
then other parcels which relied on that information will break.
Reducing the number of well known names should be a goal.
Ted
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