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Subject: RE: [xri] Draft -07 feedback from another Visa person
- From: "Wachob, Gabe" <gwachob@visa.com>
- To: "'xri@lists.oasis-open.org'" <xri@lists.oasis-open.org>
- Date: Thu, 28 Aug 2003 16:06:26 -0700
[3rd
time's a charm?]
Initial responses to comments below:
---------
XRI
Comments
340-341 Why
are cross references only absolute? For simplicity
or
conciseness? Is this
just a nomenclature issue?
i.e.
identifiers (relative, etc) satisfy
local
cross-referencing
needs?
Cross references are absolute
mostly because its not clear what the context for the identifier would be
if it *weren't* absolute. That is, if a relative identifier were used, then what
root namespace would have been defined
in?
I think there may also be some
logical reasons having to do with the motivations for cross references.
That is, the purpose of a cross reference is to use an identifier defined
elsewhere in another namespace/identifier community. Coming from
"elsewhere" implies, generally, that an identifier needs to be
globally uniquely identified -- thus the requirement of being absolute.
146 Is scheme
interoperability with HTTP a requirement or
fringe?
My personal opinion is that its not a core feature or
requirement, though it could be important in the transition to using
XRIs.
482-483 Scheme also indicates a
connection/transport protocol. In
XRI
this is lost, which
eliminates the possibility of inferring
a
default port. I would
argue that you might want to add
some
language here
like:
"Within a federated namespace, the omission of a port
may
indicate a default port. This use is at the discretion
of
the governing namespace authority (and implementing
applications)."
Well, a host name is not
simply neccesarily resolved into an A record and then connected as a
simple TCP connection. That is, in the
DNS-specified naming authority resolution, we use SRV records, which
include port numbers. Thus, this language about being "undefined" should
probably say "meaningless" or "irrelevant" as well as undefined. Port numbers
are specified in the resulting SRV record.
511 Is
xri a valid URI scheme for an xref?
Any URI scheme is valid. If
you choose to embed an XRI URI as a cross reference, then it is
treated with the same escaping rules as other URIs and appears basically as an
opaque URI to XRI processors. Normally though, you'd insert just
an XRI value (without the scheme) which makes for a more readable, compact
syntax for cross references. For
example:
xri:/1.2.3/(=Gabe)
vs.
xri:/1.2.3/(xri:=Gabe)
519 Why
define global-xri here? I don't see the relevance.
see the answer to the
previous question
521 First use of "node"? What does it mean in the context of
XRI?
terminology out of sync ;-)
I believe the terminology this corresponds to in the BNF is
"sub-segment".
525 Is
this to imply that only when the entire XRI is in () that
it is
unresolvable? I would presume that XRIs can
include
cross-references in path-segments that are also
unresolvable.
This sentence only implies
that the following syntax indicates the entire XRI is
unresolvable:
xri:(/foo.bar/baz)
As for cross-references being
"unresolvable" - this is really a misinterpretation of "unresolvable".
Unresolvable means only that the person creating or writing down the XRI doesn't
intend for anyone to actually resolve the XRI. Whether or not the XRI can be put
through the resolution process or not is an existential question that depends on
deployment (ie are there directory entries for each sub-segment?).
Cross references are never intended to be
interpreted in any way other than as an opaque string. Thus, a "non-resolvable
cross reference" is a redundant statement.
I think the problem is the term
"non-resolvable" - it should be
"not-to-be-resolved"..
550-551 I didn't
get the meaning of persistent or re-assignable identifiers
out of
this description.
2.2.3.1 Is it
allowable to escape unicode characters? For example, if
one
wanted to express an international XRI in IA5 (ASCII)? In
this
case, the %AB format described in 2.2.3.1 is insufficient to
support
the expanded character width.
694 Does the
lack od idempotency affect semantics or syntax? I would
hope it
would only be syntax.
2.2.3.3 How
about this as an alternative?
Escape all current
escapes (%s).
Escape all syntactic elements with
cross references (parens).
Escape all
parens.
878-879 Why are
XRI authorities compared in a case-insensitive manner?
Section
3 (I still need to do some reading)
Global:
Has there
been any work on DECODING XRIs? It's not immediately
clear from
the ABNF that decoding is unambiguous.
In addition,
aside from unresolvable references, is it possible
to canonicalize
XRIs? This is a highly desireable feature
(for equivalence, at
a minimum).
An XRI is
not a URI (because of the expanded syntax). But
is an URI an
XRI? (no, because of different scheme (xri)).
I think it would
be nice to all URIs be valid XRIs.
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