RE: [xri-editors] Xref escaping rules

["Dave McAlpin" <dave.mcalpin@epokinc.com>]

Yeah, I think each pass requires that % be escaped again so the whole thing
unwinds correctly.

> -----Original Message-----
> From: Drummond Reed [mailto:drummond.reed@onename.com]
> Sent: Monday, June 30, 2003 6:57 PM
> To: Wachob, Gabe; Dave McAlpin; xri-editors@lists.oasis-open.org
> Subject: RE: [xri-editors] Xref escaping rules
>
>
> Dave, I agree, very nice, very clear. One question: is escaping the %
> sign itself necessary on each pass? In other words, if a native URI
> already contains an escape sequence, such as %3F, does it need to be
> re-escaped each time it is enclosed as a cross-reference (potentially
> multiple times)?
>
> I suspect the answer is yes because this is how the algorithm stays
> clean and simple (like your logic). If so, just nod your head.
>
> =Drummond
>
> -----Original Message-----
> From: Wachob, Gabe [mailto:gwachob@visa.com]
> Sent: Monday, June 30, 2003 4:01 PM
> To: 'Dave McAlpin'; Drummond Reed; Wachob, Gabe;
> xri-editors@lists.oasis-open.org
> Subject: RE: [xri-editors] Xref escaping rules
>
> That sounds great Dave, after a quick reading. Captures my thinking and
> seems good to me.
>
> +1000
>
>         -Gabe
>
> > -----Original Message-----
> > From: Dave McAlpin [mailto:dave.mcalpin@epokinc.com]
> > Sent: Monday, June 30, 2003 3:59 PM
> > To: 'Drummond Reed'; 'Wachob, Gabe'; xri-editors@lists.oasis-open.org
> > Subject: RE: [xri-editors] Xref escaping rules
> >
> >
> > Here's the proposed text around this issue if you're interested.
> >
> > XRIs MUST use escaped encoding as described in [RFC2396].
> > XRIs also have
> > additional escaping rules described below.
> >
> > XRIs can contain nested URIs as cross-references (see section
> > [TODO]). These
> > nested URIs can contain characters that, if unescaped, would cause
> > misinterpretation when parsing the enclosing XRI. Consider
> > the following
> > XRI.
> >
> > xri:@example/(http://www.example.com?id=1)
> >
> > The generic parsing algorithm described in [RFC2396] would
> > separate the
> > above XRI into the following components
> >
> > scheme = xri
> > authority = <undefined>
> > path = @example/(http://www.example.com?
> > query = id=1)
> >
> > The desired separation is
> >
> > scheme = xri
> > authority = <undefined>
> > path = @example/(http://www.example.com?id=1)
> > query = <undefined>
> >
> > To avoid this type of misinterpretation, a URI (including an
> > XRI) must be
> > escaped before it can be used as a cross-reference. In
> > particular, it  MUST
> > be converted such that the percent "%" character is escaped
> > as "%25", the
> > question mark "?" character is escaped as "%3F" and the pound
> > sign "#" is
> > escaped as "%28".
> >
> > The example above, then, would be correctly expressed as
> >
> > xri:@example/(http://www.example.com%3Fid=1)
> >
> > Cross-references may be nested to any depth. The above rule
> > is applied to
> > each nesting level. For example, if the above XRI was used as a
> > cross-reference, the percent sign "%" would be escaped to "%25".
> >
> > xri:@example1/( xri:@example/(http://www.example.com%253Fid=1))
> >
> > Furthermore, parentheses "(" and ")" MUST be escaped if they
> > appear in a URI
> > but do not delimit an XRI cross-reference.  If an XRI
> > cross-reference is
> > embedded within an enclosing cross-reference, the parentheses
> > delimiting the
> > inner cross-reference MAY be escaped, but this is NOT
> > RECOMMENDED because it
> > complicates comparison. For example
> >
> > xri:@example1/( xri:@example/(http://www.example.com%253Fid=1))
> >
> > is preferred to
> >
> > xri:@example1/( xri:@example/%28http://www.example.com%253Fid=1%29)
> >
> > although both are legal and equivalent.
> >
> > Before a URI may be used as a cross-reference, then, the
> > following steps
> > MUST be performed in order:
> >
> > 1.    Escape all percent "%" characters as "%25".
> > 2.    Escape all parentheses "(" and ")" that do not delimit XRI
> > cross-references as "%28" and "%29", respectively.
> > 3.    Escape all pound "#" characters as "%23".
> > 4.    Escape all question mark "?" characters as "%3F".
> >
> > Note that the URI is assumed to be in an "escaped" form
> > appropriate to its
> > scheme before the above rules are applied.
> >
> > Before a cross-reference is evaluated it MUST first be unescaped. If a
> > cross-reference is contained in an enclosing cross-reference,
> > the enclosing
> > cross-reference MUST be unescaped before the inner cross-reference is
> > evaluated and unescaped.
> >
> > -----Original Message-----
> > From: Drummond Reed [mailto:drummond.reed@onename.com]
> > Sent: Monday, June 30, 2003 2:30 PM
> > To: Dave McAlpin; Wachob, Gabe; xri-editors@lists.oasis-open.org
> > Subject: RE: [xri-editors] Xref escaping rules
> >
> > +2 (except that it's %28 not #28).
> >
> > =Drummond
> >
> > -----Original Message-----
> > From: Dave McAlpin [mailto:dave.mcalpin@epokinc.com]
> > Sent: Monday, June 30, 2003 1:41 PM
> > To: 'Wachob, Gabe'; Drummond Reed; xri-editors@lists.oasis-open.org
> > Subject: RE: [xri-editors] Xref escaping rules
> >
> > Sorry, I misunderstood the question. I'm allowing both in the
> > normative
> > text
> > and saying the second is preferred.
> >
> > -----Original Message-----
> > From: Wachob, Gabe [mailto:gwachob@visa.com]
> > Sent: Monday, June 30, 2003 1:35 PM
> > To: 'Dave McAlpin'; Wachob, Gabe; 'Drummond Reed';
> > xri-editors@lists.oasis-open.org
> > Subject: RE: [xri-editors] Xref escaping rules
> >
> > Really?
> >
> > So you'd prefer:
> >
> > xri://foo.bar/(+Gabe/#28+stuff#29)
> >
> > over
> >
> > xri://foo.bar/(+Gabe/(+stuff))
> >
> > I don't see a reason why we need to do escaping for the () on
> > XRI values
> > as
> > cross references..
> >
> >         -Gabe
> >
> > > -----Original Message-----
> > > From: Dave McAlpin [mailto:dave.mcalpin@epokinc.com]
> > > Sent: Monday, June 30, 2003 12:48 PM
> > > To: 'Wachob, Gabe'; 'Drummond Reed';
> > xri-editors@lists.oasis-open.org
> > > Subject: RE: [xri-editors] Xref escaping rules
> > >
> > >
> > > I think these rules apply to cross-references in general,
> > > both general URIs
> > > and XRIs.
> > >
> > > -----Original Message-----
> > > From: Wachob, Gabe [mailto:gwachob@visa.com]
> > > Sent: Monday, June 30, 2003 12:05 PM
> > > To: 'Dave McAlpin'; Wachob, Gabe; 'Drummond Reed';
> > > xri-editors@lists.oasis-open.org
> > > Subject: RE: [xri-editors] Xref escaping rules
> > >
> > > Dave-
> > >       This seems straightforward and I don't know why it
> > > wasn't the first
> > > proposal on the table. I can't seem to figure out a problem
> > > with it, so +1
> > > unless someone can discover an issue with it.
> > >
> > >       BTW, the way I read it is that this escaping is only
> > > neccesary for
> > > URIs as xrefs, not XRI values as xrefs...
> > >
> > >       -Gabe
> > >
> > > > -----Original Message-----
> > > > From: Dave McAlpin [mailto:dave.mcalpin@epokinc.com]
> > > > Sent: Monday, June 30, 2003 10:08 AM
> > > > To: 'Wachob, Gabe'; 'Drummond Reed';
> > > xri-editors@lists.oasis-open.org
> > > > Subject: RE: [xri-editors] Xref escaping rules
> > > >
> > > >
> > > > I assumed we would escape iteratively, once for each level
> > > of nesting
> > > >
> > > > 1) Embed http://foo.com?id=21#bar in xri:@foo/baz as a
> > > cross-reference
> > > >
> > > > a) Escape cross-reference to get
> > > > http://foo.com%3Fid=21%23bar
> > > >
> > > > b) Add as cross-reference
> > > > xri:@foo/baz/(http://foo.com%3Fid=21%23bar)
> > > >
> > > > When the cross-reference is extracted, it's unescaped to
> > > >
> > > > http://foo.com?id=21#bar
> > > >
> > > > 2) Embed http://foo.com?id=21-%28widget#bar in xri:@foo/baz as a
> > > > cross-refrence
> > > >
> > > > a) Escape the cross-reference to get
> > > > http://foo.com%3Fid=21-%2528widget%23bar
> > > >
> > > > b) Append as cross-reference
> > > > xri:@foo/baz/(http://foo.com%3Fid=21-%2528widget%23bar)
> > > >
> > > > When the cross-reference is extracted, it's unescaped to
> > > >
> > > > http://foo.com?id=21-%28widget#bar
> > > >
> > > > 3) A complex nested example. Embed
> > http://foo.com?id=21-%28widget in
> > > > xri:+foo.bar.<xref>, which is in turn embedded in
> > > > xri://foo.bar/<xref>/baz
> > > >
> > > > a) First escape the innermost cross-reference to get
> > > > http://foo.com%3Fid=21-%2528widget
> > > >
> > > > b) Add as cross-reference
> > > > xri:+foo.bar.(http://foo.com%3Fid=21-%2528widget)
> > > >
> > > > c) Escape the cross-reference to get
> > > > xri:+foo.bar.(http://foo.com%253Fid=21-%252528widget)
> > > >
> > > > d) Add as cross-reference
> > > > xri://foo.bar/(xri:+foo.bar.(http://foo.com%253Fid=21-%252528w
> > > > idget)))/baz
> > > >
> > > > When the XRI is evaluated, the outermost cross-reference is
> > > extracted
> > > >
> > > > xri:+foo.bar.(http://foo.com%253Fid=21-%252528widget))
> > > >
> > > > And unescaped to give
> > > >
> > > > xri:+foo.bar.(http://foo.com%3Fid=21-%2528widget))
> > > >
> > > > The next level cross-reference is extracted
> > > >
> > > > http://foo.com%3Fid=21-%2528widget
> > > >
> > > > and unescaped to give
> > > >
> > > > http://foo.com?id=21-%28widget
> > > >
> > > > Dave
> > > >
> > > > -----Original Message-----
> > > > From: Wachob, Gabe [mailto:gwachob@visa.com]
> > > > Sent: Monday, June 30, 2003 9:19 AM
> > > > To: 'Drummond Reed'; xri-editors@lists.oasis-open.org
> > > > Subject: RE: [xri-editors] Xref escaping rules
> > > >
> > > > Drummond-
> > > >     This seems pretty reasonable.
> > > >
> > > >     Have you considered the case where you have two
> > levels of cross
> > > > referencing? That is, a cross reference which contains an XRI
> > > > value that
> > > > itself has a cross reference?
> > > >
> > > > xri://foo.bar/(+foo.bar.(http://www.foo.com#3ffoo))/baz
> > > >
> > > > vs
> > > >
> > > > xri://foo.bar/(+foo.bar.(http://www.foo.com(#3f)foo))/baz
> > > >
> > > > vs
> > > >
> > > > xri://foo.bar/(+foo.bar.(http://www.foo.com((#3f))foo))/baz
> > > >
> > > > I think you need to amend the rules about escaping/unescaping
> > > > to account for
> > > > nesting..
> > > >
> > > >     -Gabe
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Drummond Reed [mailto:drummond.reed@onename.com]
> > > > > Sent: Sunday, June 29, 2003 1:15 PM
> > > > > To: xri-editors@lists.oasis-open.org
> > > > > Subject: [xri-editors] Xref escaping rules
> > > > >
> > > > >
> > > > > Here's the escaping proposal that I brought up on the
> > > last TC call.
> > > > >
> > > > > The issue is that an XRI or URI is used as a cross-reference
> > > > > may contain
> > > > > characters that must be escaped in order to conform with 2396.
> > > > > Specifically:
> > > > >
> > > > > * "?" may not appear until the start of the one-and-only
> > > > query segment
> > > > > allowed by 2396.
> > > > > * The same is true with "#" for fragments
> > > > > * Lastly, an UNMATCHED opening or closing paren must be
> > > > > escaped or else
> > > > > the cross-reference will not parse correctly. (Note that
> > > > > MATCHED opening
> > > > > and closing parens inside do not need escaping because they
> > > > represent
> > > > > either a second-level nested cross-reference or a
> > parenthetically
> > > > > enclosed string in a native URI but either way will not be
> > > > ambiguous.)
> > > > >
> > > > > However we can't use just 2396 escaping rules (i.e., "%xx"
> > > > where xx is
> > > > > the hex value of the character) for these four characters
> > > > > because it if
> > > > > the embedded XRI or URI contained those same escape sequences
> > > > > natively,
> > > > > it would be ambiguous which to unescape and not to
> > > unescape when the
> > > > > cross-reference is extracted. For example, if a URI already
> > > > contained
> > > > > the escape sequence %3F (the "?" character) before it was
> > > > > turned into a
> > > > > cross-reference, how would the parser know NOT to
> > unescape it when
> > > > > extracting the cross-reference?
> > > > >
> > > > > The proposed solution is to apply two special escaping
> > > rules to any
> > > > > URI/XRI string being embedded as a cross-reference. They must
> > > > > be applied
> > > > > in the following order:
> > > > >
> > > > > 1) Parse the string to find any instance of "%3F", "%23",
> > > "%28", or
> > > > > "%29" and enclose these in parens. Example: "(%3F)".
> > > > > 2) Escape any "?", "#", or UNMATCHED paren as per 2396 escaping.
> > > > > Example: a URI that contained a query would have the "?"
> > > turned into
> > > > > %3F.
> > > > >
> > > > > To extract a cross-reference, apply the same two rules in
> > > > > reverse, i.e.:
> > > > >
> > > > > 1) From the extracted cross-reference, escape any instance of
> > > > > %3F, %23,
> > > > > %28, or %29 EXCEPT those enclosed in parens.
> > > > > 2) For any instance of "%3F", "%23", "%28", or "%29" enclosed
> > > > > in parens,
> > > > > remove the parens.
> > > > >
> > > > > Example:
> > > > >
> > > > > Embed: URI "http://foo.com/?id=21#bar" in XRI "xri:@foo/baz/"
> > > > > Result: "xri:@foo/baz/(http://foo.com/%3Fid=21%23bar)"
> > > > >
> > > > >
> > > > > Embed: URI "http://foo.com/?id=21-%28widget#bar" in XRI
> > > > > "xri:@foo/baz/"
> > > > > Result:
> > "xri:@foo/baz/(http://foo.com/%3Fid=21-(%28)widget%23bar)"
> > > > >
> > > > > Does this work for everyone? Any other proposals?
> > > > >
> > > > > =Drummond
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > >
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