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Subject: RE: [xri] RE: GCS chars and star in XRI authority resolution
While the ABNF is nominally simpler using the production below, it makes XRIs less regular and harder to understand from a human perspective. If we allow "@!", I belive that we need a very strong reason not to also allow "@*".
Mike
> -----Original Message-----
> From: Drummond Reed [mailto:drummond.reed@cordance.net]
> Sent: Monday, August 23, 2004 5:56 PM
> To: Lindelsee, Mike ; xri@lists.oasis-open.org
> Subject: RE: [xri] RE: GCS chars and star in XRI authority resolution
>
>
> In retrospect I believe we erred in the 1.0 BNF in allowing
> what was then
> dot (and is now star) after a GCS character. I believe a
> cleaner approach in
> XRI 1.1 would be the following rationale:
>
> 1) All the GCS chars except "!" are "proxies" for "*", in
> that they default
> to a reassignable subsegment.
>
> 2) Therefore, there is no need for * following a GCS character. It is
> redundant - the equivalent of "**", which makes no sense.
>
> 3) Therefore the simplest rule, which eliminates any confusion and any
> chance of false negatives in a equivalence comparision, is
>
> GCS-authority = gcs-char [ "!" ] [ nz-segment ]
>
> Also, to keep XRI resolution consistent, the GCS char would be treated
> exactly the same as star in subsegment resolution, i.e., it would be
> submitted as part of the string being resolved when resolving
> against a GCS
> root. For example, when resolving "@foo*bar", the string
> submitted to the
> "@" authority would be "@foo", and the string submitted to the "@foo"
> authority would be "*bar".
>
> =Drummond
>
>
> -----Original Message-----
> From: Lindelsee, Mike [mailto:mlindels@visa.com]
> Sent: Monday, August 23, 2004 3:57 PM
> To: xri@lists.oasis-open.org
> Subject: [xri] RE: GCS chars and star in XRI authority resolution
>
> My preference would be to stick to a completely regular syntax. I.e.,
> always prefix the sub-segment that follows the GCS char with
> a "*" or a "!",
> but I realize that this won't be satisfactory for many
> others, so I think we
> should stick with xri 1.0 rules/syntax wrt this issue and
> allow any of:
>
> xri:@foo
> xri:@!foo
> xri:@*foo
>
> where xri:@foo is equivalent to xri:@*foo.
>
> Mike
>
> > -----Original Message-----
> > From: Drummond Reed [mailto:drummond.reed@cordance.net]
> > Sent: Friday, August 20, 2004 3:15 PM
> > To: Lindelsee, Mike ; xri@lists.oasis-open.org
> > Subject: GCS chars and star in XRI authority resolution
> >
> >
> > Per the question Mike raises: "The inclusion (or not) of the
> > delimiter that
> > indicates reassignability or persistence in the sub-segment
> that gets
> > resolved is something that we'll still need to discuss as we revisit
> > resolution for 1.1."
> >
> > I'd like to propose something I think will make both
> > equivalence and XRI
> > authority resolution simpler in 1.1.
> >
> > Per the BNF I just posted following Dave's suggestion, a GCS-rooted
> > authority segment would be:
> >
> > GCS-authority = gcs-char [ "!" / "*" ] [ nz-segment ]
> >
> > Therefore a GCS char can be followed by either an nz-segment,
> > or !, or *. So
> > the following are all legal:
> >
> > @foo
> > @*foo
> > @!foo
> >
> > In XRI 1.0 we treated "@foo" and "@*foo" as equivalent. We
> > said the * was
> > "assumed" with any GCS char.
> >
> > In XRI 1.1 I'd propose that we simplify things in one of two ways:
> >
> > OPTION 1: BY NOT DEFINING GCS-CHAR AND GCS-CHAR* AS EQUIVALENT
> >
> > Instead, the rules would be that:
> >
> > 1) By default, the nz-segment following a GCS char is reassignable.
> > 2) In XRI authority resolution, if EITHER ! or * preceed an
> > nz-sub-segment,
> > they are treated as part of the nz-sub-segment from the
> standpoint of
> > resolution, i.e., are part of the value being resolved.
> >
> > By these rules, @foo, @*foo, and @!foo are all different
> > values. "foo" is a
> > reassignable sub-segment in both "@foo" and "@*foo" by
> definition, but
> > "@foo" and "@*foo" are not equivalent.
> >
> > OPTION 2: BY NOT ALLOWING * DIRECTLY AFTER A GCS CHAR
> >
> > In ths option, the BNF would be:
> >
> > GCS-authority = gcs-char [ "!" ] [ nz-segment ]
> >
> > Again, the same two rules proposed in Option 1 would apply.
> > Only now you can
> > just have "@foo" and "@!foo", because "@*foo" is illegal.
> >
> > I believe this is actually the option most consistent with
> > the rule that by
> > default, the nz-sub-segment following a GCS char is
> > reassignable, because it
> > means that the * is already inherent in the GCS char, just
> > the way it is
> > inherent in a slash (reassignable sub-segment being the
> default after
> > slash).
> >
> > Which do folks prefer?
> >
> > =Drummond
> >
> >
> > -----Original Message-----
> > From: Lindelsee, Mike [mailto:mlindels@visa.com]
> > Sent: Friday, August 20, 2004 2:10 PM
> > To: xri@lists.oasis-open.org
> > Subject: RE: RE: [xri] Initial proposed XRI 1.1 ABNF and
> > issues analysis
> >
> > Bill,
> >
> > I'm not clear which XRI ABNF you are asking your questions
> > with respect to.
> > I don't believe that the XRI below (xri:@example*:23:45)
> > would be valid
> > using XRI 1.0 syntax ('*' is only allowed as a GCS character
> > in 1.0). The
> > XRI also wouldn't be valid in the original 1.1 ABNF ('*'
> and ':' can't
> > follow one another). It would be valid in the various
> > iterations of the ABNF
> > that Dave, Drummond and I have been discussing on the list --
> > though the
> > interpretation of the sub-segments might be slightly
> > different between the
> > various iterations.
> >
> > The latest proposal would break the XRI up as follows:
> >
> > 1: @
> > 2: *example (reassignable sub-segment - and showing
> > implicit delimiter)
> > 3: *:23:45 (reassignable sub-segment)
> >
> > The inclusion (or not) of the delimiter that indicates
> > reassignability or
> > persistence in the sub-segment that gets resolved is
> > something that we'll
> > still need to discuss as we revisit resolution for 1.1.
> >
> > Mike
> >
> > > -----Original Message-----
> > > From: Barnhill William [mailto:barnhill_william@bah.com]
> > > Sent: Friday, August 20, 2004 11:03 AM
> > > To: Lindelsee, Mike
> > > Cc: xri@lists.oasis-open.org
> > > Subject: Re: RE: [xri] Initial proposed XRI 1.1 ABNF and
> > > issues analysis
> > >
> > >
> > > Looks good to me as well, but some questions...
> > > (1) Is this XRI valid? xri:@example*:23:45
> > > (2) If valid, would it represent 4 resolution steps:
> > > 1: @
> > > 2: .example
> > > 3: *:23
> > > 4: *:45
> > > With the '. on 1: and the '*' on 4 being implicitly stated.
> > >
> > > (3) If the above XRI is suppose to respresent 4 resolution
> > > steps do not
> > > the new rules result in only 3 steps? As :23:45 would be
> > > considered one
> > > segment.
> > >
> > > Thanks,
> > >
> > > Bill Barnhill
> > >
> >
> >
> >
>
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