RE: [xri-editors] Xref escaping rules

["Drummond Reed" <drummond.reed@onename.com>]

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
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> >
> ---------------------------------------------------------------------
> > > > To unsubscribe, e-mail:
> > xri-editors-unsubscribe@lists.oasis-open.org
> > > > For additional commands, e-mail:
> > > xri-editors-help@lists.oasis-open.org
> > > >
> > >
> > >
> >
> ---------------------------------------------------------------------
> > > To unsubscribe, e-mail:
> xri-editors-unsubscribe@lists.oasis-open.org
> > > For additional commands, e-mail:
> > xri-editors-help@lists.oasis-open.org
> > >
> > >
> > >
> > >
> > >
> >
> ---------------------------------------------------------------------
> > > To unsubscribe, e-mail:
> xri-editors-unsubscribe@lists.oasis-open.org
> > > For additional commands, e-mail:
> > xri-editors-help@lists.oasis-open.org
> > >
> >
> >
> ---------------------------------------------------------------------
> > To unsubscribe, e-mail: xri-editors-unsubscribe@lists.oasis-open.org
> > For additional commands, e-mail:
> xri-editors-help@lists.oasis-open.org
> >
> >
> >
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: xri-editors-unsubscribe@lists.oasis-open.org
> For additional commands, e-mail: xri-editors-help@lists.oasis-open.org
>
>
>
>