Title: RE: [xri] Initial proposed XRI 1.1 ABNF and issues analysis
Good
point. Your changes work for me.
Mike
-----Original Message-----
From: Drummond Reed
[mailto:]
Sent: Thursday, August 19, 2004
11:01 PM
To: Lindelsee, Mike ;
Subject: RE: [xri] Initial proposed XRI 1.1
ABNF and issues analysis
Problem: this last
BNF would not allow xri-auth-delims (! and *) in a path
segment.
I'm thinking that
while the initial proposal to generalize the subsegment delimiters was
intended to make things simpler, the problem Mike pointed out actually makes
it more complex than another approach: putting just two delimiters (! and *)
into "xri-sub-delims", then putting all the rest of the URI sub-delims into a
new "xri-alt-delims". Now xri-pchar can include xri-alt-delims just like URI
pchar includes URI sub-delims in RFC2396bis.
So we'd
have:
xri-gen-delims
= "/" / "?" / "#" / "[" / "]" / "@" / "(" /
")" / "$" / "+" / "="
xri-sub-delims
= "!" / "*"
xri-alt-delims
= "&" / ":" / ";" / "," / "'"
xri-pchar =
xri-unreserved / pct-encoded / xri-alt-delims
sub-segment
= ( *xri-pchar / xref )
nz-sub-segment = (
1*xri-pchar / xref )
xri-segment
= sub-segment *( xri-sub-delims sub-segment
)
nz-segment =
nz-sub-segment *( xri-sub-delims nz-sub-segment
)
XRI-authority = ( gcs-char [xri-sub-delims] [
nz-segment ] ) / xref-authority
relative-path =
xri-segment * ( "/" xri-segment ) [ "?" xri-query
]
[ "#" xri-fragment ]
xref-authority = xref *(
xri-sub-delims nz-sub-segment )
=Drummond
From:
Lindelsee, Mike [mailto:]
Sent: Thursday, August 19, 2004 2:25 PM
To:
Subject: RE: [xri] Initial proposed XRI
1.1 ABNF and issues analysis
It seems to me that
if we drop xri-path-delim (absorb those characters back into xri-sub-delim),
and include xri-auth-delim in xri-gen-delim (and correct the relevent
productions), we solve Dave's first concern. Fixing the XRI authority to
support "@!" (as well as the rest of the GCS characters) is
actually really easy in a consistent way -- just add an optional
xri-auth-delims after the gcs-char in the XRI-authority production (see below
for the updated ABNF productions). Changing the production would allow
for "@*" as well. While we can probably consider this as the default
meaning of a single GCS character (such as "@"), I like the regularity of
supporting it explicity.
The problem that I
have with allowing the characters in xri-sub-delims both delimit a sub-segment
and to be part of a sub-segment (by being part of xri-pchar) is that it
creates an ambiguity as to what constitutes a sub-segment. For
example, is the local path in the following xri composed of 2 or 3
sub-segments?
xri://@corp/a;b;c
According to the ABNF
(if xri-sub-delims are both used in the xri-path-segment production and in the
xri-pchar production), one could consider the sub-segments to be (1) a, b, and
c, (2) a;b and c, or (3) a and b;c. I'd prefer to avoid introducing the
ambiguity if at all possible.
My recommendation is
to make the changes below and also exclude xri-sub-delims from the xri-pchar
production.
Mike
Updated Changes to
ABNF
---------------------------------------
xri-sub-delims
= "&" / ":" / ";" / "," / "'"
xri-auth-delims =
"!" / "*"
xri-gen-delims
= "/" / "?" / "#" / "[" / "]" / "@" / "("
/
"(" / ")" / "$" / "+" / "=" / xri-auth-delims
xri-auth-segment =
auth-sub-segment *( xri-auth-delims auth-sub-segment
)
xri-path-segment = path-sub-segment *( xri-sub-delims
path-sub-segment )
XRI-authority = ( gcs-char
[xri-auth-delims] [ xri-auth-segment ] ) /
xref-authority
relative-path = xri-path-segment * (
"/" xri-path-segment ) [ "?" xri-query
]
[ "#" xri-fragment ]
xref-authority = xref *(
xri-auth-delims auth-sub-segment )
auth-sub-segment = (
1*xri-pchar / xref )
path-sub-segment = ( *xri-pchar /
xref )
xri-pchar =
xri-unreserved / pct-encoded / xri-sub-delims
-----Original
Message-----
From: Drummond
Reed [mailto:]
Sent: Wednesday, August 18, 2004
4:20 PM
To: 'Dave McAlpin'; Lindelsee, Mike ;
Subject: RE: [xri] Initial proposed XRI
1.1 ABNF and issues analysis
Agreed. Then, Dave,
do you agree with Mike's suggestion of creating a new "delims" category for
xri-auth-delims?
I'm beginning to
wonder if the generalized treatment of subsegments in the proposed XRI 1.1
path is worth the trouble. Would it be simpler to just define * and ! as the
two sub-delimins and then let the other subdelims be part of the path? That
way they will be available for all producer-specific algorithms
anyway
Mike, do you think
it would be simpler to just have an "xri-path-delim" production for * and !
? In that case the XRI authority segment and the path segments could go back
to being the same.
Mike, one thing
that occurred to me this morning: we can't eliminate null subsegments in the
XRI authority segment without knocking out using ! after a GCS character
(e.g., "@!1234"), as by the current BNF, ! is proceeded by a null
subsegment. We'd either have to otherwise change the BNF to support that
(taking us back into "decorator" land) or simply have tight resolution rules
about null subsegments.
=Drummond
From: Dave
McAlpin [mailto:]
Sent: Wednesday, August 18, 2004
2:51 PM
To: Lindelsee, Mike ;
Subject: RE: [xri] Initial proposed XRI
1.1 ABNF and issues analysis
Unless there's a compelling reason to do otherwise,
I'd suggest that we move "*" and "!" back to
xri-gen-delims.
Dave
-----Original Message-----
From:
Lindelsee, Mike [mailto:]
Sent: Wed
8/18/2004 1:13 PM
To:
Subject: RE: [xri]
Initial proposed XRI 1.1 ABNF and issues analysis
Do you think that
we should place "*" and "!" in gen-delims then? Or are my proposed
changes ok as they stand?
Mike
-----Original
Message-----
From: Dave McAlpin [mailto:]
Sent:
Wednesday, August 18, 2004 12:58 AM
To: Lindelsee, Mike ;
Subject: RE: [xri] Initial proposed XRI 1.1 ABNF
and issues analysis
I intentionally included xri-sub-delims
in xri-pchar, and this was correct in the original ABNF. Since then, someone
moved sub-segment delimiters from xri-gen-delims to xri-sub-delims. I think
this is just a misunderstanding of what I intended for xri-sub-delims. The
idea (borrowed from 2396bis), is that xri-gen-delims are delimiters for
which we define semantics and are reserved for the purpose defined in the
spec. In contrast, xri-sub-delims are reserved as delimiters with no defined
semantics, intended for processor specific
algorithms.
Dave
-----Original Message-----
From:
Lindelsee, Mike [ mailto:]
Sent: Tue
8/17/2004 4:23 PM
To:
Subject: [xri] Initial
proposed XRI 1.1 ABNF and issues analysis
I've taken a look at the
proposed ABNF and would like to recommend a couple of changes. First,
I think we should be relatively strict in the authority part and restrict
the segment delimiters to only those that are valid delimiters. My
concern is that showing other delimeters in the authority part will imply to
people reading the ABNF that those delimiters might have some sort of
meaning. The second change is to remove the support for null segments
in the authority part. While there is an XDI use for null segments in
the path part, it doesn't seem to be needed in the authority part. And
not allowing null segments in the authority part helps to keep resolution as
simple as possible.
I also noticed what might be a bug -- the
inclusion of xri-sub-delims in the xri-pchar production. This allows
segment delimiters to be embedded within segments. I don't think that
this makes sense (Dave, please correct me if I'm wrong on
this).
Mike
Proposed changes to the updated XRI
ABNF
----------------------------------------
(change)
xri-sub-delims = xri-auth-delims /
xri-path-delims
(add)
xri-auth-delims = "!" /
"*"
(add)
xri-path-delims = "&" / ":" / ";" / "," /
"'"
(remove)
xri-segment
= sub-segment *( xri-sub-delims sub-segment
)
(add)
xri-auth-segment =
auth-sub-segment *( xri-auth-delims auth-sub-segment
)
(add)
xri-path-segment =
path-sub-segment *( xri-sub-delims path-sub-segment
)
(change)
XRI-authority = ( gcs-char [ xri-auth-segment ] ) /
xref-authority
(change)
relative-path = xri-path-segment * ( "/" xri-path-segment
) [ "?" xri-query
]
[ "#" xri-fragment ]
(change)
xref-authority = xref *( xri-auth-delims auth-sub-segment
)
(remove)
sub-segment
= ( *xri-pchar / xref
)
(add)
auth-sub-segment = (
1*xri-pchar / xref
)
(add)
path-sub-segment = ( *xri-pchar / xref
)
(change-bug)xri-pchar
= xri-unreserved /
pct-encoded
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