Hierarchical namespaces?

james anderson James.Anderson at mecomnet.de
Mon Jan 3 11:30:23 GMT 2000

hierarchical namespaces provide the ability to establish symbol identity
indirectly by specifying a network of inheritance relationships among the sets
of names which the respective namespaces entail.

were the concepts and appropriate mechanisms to be made available in the xml
domain, they could be used, for example, to implement versioning and would be
one way to approach problems like the "multi-namespace-html" issue.

one possible analog is the package system in common lisp, which provides the
means to declare relationships among sets of symbols as well as relationships
among individual symbols.

the primitives support such things as
 specifying a symbol's membership in a set
 specifying visibility from outside the set
 specifying inheritance of visible symbols between two sets
 specifying limits to visibility from inside a set

please note, that these have nothing to do with what a given symbol may be
bound to, just with its identity.

given these facilities, the application can take the opportunity, when it
declares the "known" names in preparation for specifying processing methods,
to specify that ostensibly distinct names - that is, those with non identical
encodings, are in fact the same name and to be processed in the same way.
while it is true, that it's a shorthand only, it does make the application a
lot easier to code.

Clark C. Evans wrote:
> That being said, I had never expected a set of namespaces
> to have value by organizing them hierarchially... so I'm
> wondering exactly what value a hierarchy of namespaces would
> provide?  Would it be a sequence of ever-so-much-more-specific
> schemas?  Where the most specific definition is the binding
> one? I can't think of any other reasons why I'd have more
> than one namespace for a given "domain", let alone a
> hierarchically organized set.  What am I missing?

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