RE: naming contexts

Kurt,

> It seems to me that the definition of a "naming context"
> in LDAP/X.500 makes little sense in the face of multi-master
> replication.  A LDAP/X.500 naming context is subtree of
> entries held in a single master DSA.
>
> Consider three DSAs A, B, C where
> 	A masters subtree X
> 	B masters subtree Y
> 	C masters subtrees X and Y, and
> 	Subtrees X and Y are adjacent.

>From what follows, I assume that Y is subordinate to X.

> If A and B are masters and C is a shadow of each,
> LDAP/X.500 says that
> 	A holds context X, B holds context Y, and
> 	C holds contexts X and Y.

C holds a shadow copy of contexts X and Y.

> If C masters X and Y and A and B are shadows,
> LDAP/X.500 says that:
> 	A, B, C holds context X

C holds context X, which is now the union of the subtrees X and Y,
i.e. there is no longer a context Y. A holds a shadow copy of a
portion (subtree X) of context X. B holds a shadow copy of a different
portion (subtree Y) of context X.
>
> If A, B, and C master the subtrees they hold, which
> contexts does LDUP say they hold?

Having an entry mastered by more that one master DSA doesn't invalidate
the definition of naming context as far as I can see, but we do need
to be a bit more careful how we phrase things.

A holds a naming context with the context prefix being the root of the
subtree X. B holds a naming context with the context prefix being the
root of the subtree Y. C holds a naming context with the context prefix
being the root of subtree X, the same root as A but with a superset of the
entries. Off the top of my head I can't think of anything that is broken
because A and C have the same context prefix but unequal sets of entries
in their naming contexts.

For LDUP we're okay if we say we are replicating "replication contexts"
rather than "naming contexts". C can be said to hold two adjacent
replication
contexts (for subtree X and subtree Y).

>
> I can only find one reasonable way to answer this question,
> it requires each entry to have held by one and only one
> "primary" master DSA and defining the LDUP naming context
> as a subtree of entries held in a single "primary" master
> DSA.  I believe this same solution can be used to define
> other terms and to detail directory models for multi-master
> replication which maps reasonable well onto the X.500 models.

I don't think we need impose this restriction for
what is only a definitional problem.

>
> I recommend the WG consider defining the LDUP multi-master
> replication directory models such that, for any particular
> entry, there is only one "primary" master DSA and zero or
> more "secondary" master DSAs.   Otherwise, defining the
> models consistent with the LDAP/X.500 models will be
> extremely difficult.

Regards,
Steven