- From: Ralph R. Swick <swick@w3.org>
- Date: Thu, 02 Apr 2009 12:28:10 -0400
- To: public-rdf-in-xhtml-tf@w3.org
- Cc: public-swd-wg@w3.org
The record of today's RDFa discussion are avaialble as
http://www.w3.org/2009/04/02-rdfa-minutes.html
A text snapshot follows.
----
RDF-in-XHTML Task Force
02 Apr 2009
[2]Agenda
[2] http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2009Apr/0018.html
See also: [3]IRC log, previous [4]2009-03-19
[3] http://www.w3.org/2009/04/02-rdfa-irc
[4] http://www.w3.org/2009/03/19-rdfa-minutes.html
Attendees
Present
Ralph Swick, Manu Sporny, Shane McCarron, Mark Birbeck
Regrets
Ben_Adida, Michael_Hausenblas
Chair
Manu
Scribe
Ralph
Contents
* Topics
1. Action Review
2. Report on AC Meeting
3. @prefix syntax discussion
* Summary of Action Items
_____________________________________________________
Action Review
ACTION: [PENDING] Ben to put up information on "how to write RDFa"
with screencast possibly and instructions on bookmarklet. [recorded
in [10]http://www.w3.org/2008/11/06-rdfa-minutes.html#action12]
[10] http://www.w3.org/2008/11/06-rdfa-minutes.html#action12
ACTION: [PENDING] Jeremy to demonstrate GRDDL with XHTML/RDFa once
the NS URI is set up. [recorded in
[11]http://www.w3.org/2008/09/11-rdfa-minutes.html#action03]
[11] http://www.w3.org/2008/09/11-rdfa-minutes.html#action03
ACTION: [DONE] Manu to look at
[12]http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2008D
ec/0037.html about resolving relative URIs [recorded in
[13]http://www.w3.org/2009/01/08-rdfa-minutes.html#action15]
[12] http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2008Dec/0037.html
[13] http://www.w3.org/2009/01/08-rdfa-minutes.html#action15
Manu: I've replied and asked twice for a response
... I think they're accepting the response
... so I think we can consider this done
ACTION: [PENDING] Manu to write summary for Semantic Web Use Cases
for Ivan. [recorded in
[14]http://www.w3.org/2008/09/11-rdfa-minutes.html#action09]
[14] http://www.w3.org/2008/09/11-rdfa-minutes.html#action09
ACTION: [PENDING] Mark create base wizard suitable for cloning
[recorded in
[15]http://www.w3.org/2008/09/11-rdfa-minutes.html#action12]
[15] http://www.w3.org/2008/09/11-rdfa-minutes.html#action12
ACTION: [DONE] Mark to review reasoning on setting explicit about=""
on HEAD and BODY [recorded in
[16]http://www.w3.org/2008/12/18-rdfa-irc]
[16] http://www.w3.org/2008/12/18-rdfa-irc
-> [17]The implied @about="": Explanation and some problems Mark
2009-04-01]
[17] http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2009Apr/0000.html
ACTION: [PENDING] Mark to send Ben ubiquity related wizard stuff
[recorded in
[18]http://www.w3.org/2008/11/20-rdfa-minutes.html#action11]
[18] http://www.w3.org/2008/11/20-rdfa-minutes.html#action11
ACTION: [PENDING] Mark write foaf examples for wiki [recorded in
[19]http://www.w3.org/2008/09/11-rdfa-minutes.html#action13]
[19] http://www.w3.org/2008/09/11-rdfa-minutes.html#action13
ACTION: [PENDING] Michael to create 'RDFa for uF users' on RDFa Wiki
[recorded in
[20]http://www.w3.org/2008/09/11-rdfa-minutes.html#action14]
[20] http://www.w3.org/2008/09/11-rdfa-minutes.html#action14
ACTION: [PENDING] Ralph or Steven fix the .htaccess for the XHTML
namespace [recorded in
[21]http://www.w3.org/2009/01/08-rdfa-minutes.html#action01]
[21] http://www.w3.org/2009/01/08-rdfa-minutes.html#action01
Ralph: I know Steven poked someone about this
ACTION: [PENDING] Ralph think about RSS+RDFa [recorded in
[22]http://www.w3.org/2008/09/11-rdfa-minutes.html#action15]
[22] http://www.w3.org/2008/09/11-rdfa-minutes.html#action15
Report on AC Meeting
Manu: anyone there for the HTML discussions than Ben and Steven?
Shane: unfortunately Ben couldn't stay for the breakout session
Mark: the minutes suggest the discussion was quite positive
Ralph: I needed to participate in a different breakout
Mark: I'm looking at the minutes of the Backplane XG
Shane: there appears to be substantial support from the Membership
for the extensibility model that XHTML has always had
@prefix syntax discussion
Manu: at our last discussion, Shane and Ralph were favoring the '='
syntax and Mark and I were favoring the JSON-esque syntax
... any new thoughts in the subsequent 2 weeks?
Mark: I'm involved in a couple of projects where folk are producing
what they think is RDFa
... it's interesting; I see a growing need for tools to check the
work
... simply typos like mismatch between namespace declaration and
usage
Ralph: no real additional thoughts but I did make note of Mark's
concerns about the pattern @attr="prefix=value"
... but if tools are generating this anyway, how much does it
matter?
Mark: I'm thinking of checking tools more than generation tools
Manu: definitely think embedded '=' will cause confusion
... and people will put whitespace around the '='
... so we need resilient syntaxes and parsers
Shane: I don't think it's terribly important to have delimiters
other than whitespace between the items
... but I won't fight on that
... I understand the sensitivity to the repeated '=' issue
... do you prefer ':'?
Manu: yes
Shane: that's probably fine, but then you end up with repeated ':'
<ShaneM> perfix="xhv:http:..."
Shane: I leaned toward repeated '=' in the first place because that
made it clear which was the prefix and which was the rest
<markbirbeck> prefix="xhv:xyz dc:xyz"
<markbirbeck> prefix="xhv=xyz dc=xyz"
Mark: we're tending to discuss as if [the two examples above] were
the patterns
... this is how @xml:schemalocation works
<markbirbeck> prefix="
<markbirbeck> xhv: xyz,
<markbirbeck> dc: xyz
<markbirbeck> "
Mark: I'm thinking we should really be looking at layout such as
[above in irc]
... in this case, additional delimiters are useful; we don't need to
be compact
... we should consider not just a syntax but also examples that
people will cut & paste
... if I were to copy one of Manu's audio prefix examples I could
select a single line (of many declarations) and insert it into my
list without introducing error
... once you spread things out like this, why not allow further
flexibility
<markbirbeck> prefix="
<markbirbeck> 'xhv': 'xy z',
<markbirbeck> dc: xyz
<markbirbeck> "
Shane: my concern is that URIs allow these characters, so the syntax
rules and the parsing are both more challenging
Mark: yes, but there are extra options for delimiting
... if we say we're allowing quotes _as well_ this gives additional
flexibility
<markbirbeck> prefix="
<markbirbeck> 'xhv': 'xy z,',
<markbirbeck> dc: xyz
<markbirbeck> "
Mark: if you did have a URI that ends in ',' then quoting allows an
easy way to include it
... ':' in @xmlns was really an effort to find one thing that would
work
... but we have greater flexibility
Manu: when people mint prefix mapping URIs I find it highly unlikely
that they'll use a ',' in such a URI
... yes, it _could_ happen but if it's a well-known design
consideration that such characters cause trouble then vocabulary
developers can avoid them
Mark: what is the added complexity?
Manu: it's additional complexity in the parser. I'm questioning
whether we really need it.
Mark: it's one regular expression
... a way of trying to introduce resilience and something that
[humans] can grok easily
... we come back to this problem of recognizing what is a URI
... I'm just thinking of ways to provide resilience when needed
without mandating it all the time
<markbirbeck> prefix="
<markbirbeck> xhv: {xy z,},
<markbirbeck> dc: xyz
<markbirbeck> "
Manu: I'd like to see the regex
... my C+sax-based parser doesn't have to use regex's anywhere right
now
Mark: a space-separated list needs to be cracked into a list
... even '=' can appear in a URI
<ShaneM> index
Manu: I don't think we can count on authors writing examples
consistently
... and a mixture of styles will cause confusion
Mark: I'm proposing the _possibility_ of permitting this richer
format, not _requiring_ it
Manu: I was only questioning whether example authors will really
write the examples with multi-line declarations
<markbirbeck> prefix="xhv: xy, dc: xyz"
Manu: when the examples are written on a single line the richer
syntax becomes confusing
Mark: consider space-separated lists
<markbirbeck> prefix="xhv:xy dc:xyz"
Mark: then you can't have space around ':'
... the options for authors laying out the markup are limited
... no flexibility for aligning things [in columns]
... whereas the XML attribute syntax has a lot of flexibility, for
example; can use whitespace to nudge things [into columns]
... in terms of consistency, generally in XML spaces are ignored
... other than the use in XML Schema to create lists, whitespace is
not significant
Shane: whitespace is collapsed, not ignored
... this includes newlines
... collapsing inside attributes values
... however, this is bad; in the HTML DOM whitespace is not
collapsed
... this means a parser that has to work with both XML and HTML has
to be written to expect multiple whitespace
Mark: but the presence of whitespace is geenerally not significant
... as long as there is whitespace in key places, such as between
attributes
... '=' vs. ':' is a separate discussion from whether whitespace is
a delimiter
Manu: I agree; we shouldn't decide solely on whitespace
<msporny> prefix="xhv:xy, dc:xyz" prefix="xhv:xy; dc:xyz"
Manu: for delimiters between mappings, we're considering something
like ^
Shane: a lot of our canonical examples are ones that contain ',';
e.g. Wikipedia or Amazon
... places where, for example, an ISBN might be interpolated
<msporny> prefix="media: [23]http://purl.org/media#, audio:
[24]http://purl.org/media/audio#"
[23] http://purl.org/media
[24] http://purl.org/media/audio
Mark: yeah, can't quickly come up with an example
<markbirbeck> mapping, mapping, mapping
Mark: should treat as mapping, mapping, mapping
... then decide what goes inside mapping
<msporny> prefix="media: [25]http://purl.org/media# ; audio :
[26]http://purl.org/media/audio#"
[25] http://purl.org/media
[26] http://purl.org/media/audio
Shane: can't just be 'ends in comma' -- must be 'includes comma'
Manu: are Shane and Ralph ok with using ',' between mappings?
Shane: if we're going to use ',' or ';' we need to define the
escaping mechanism
... maybe there's already a mechanism defined somewhere
... my preferred syntax is identical to schemalocation [i.e.
alternation] but Ralph says that's a non-starter
Manu: ok to pick a character that must be URI-encoded in URIs?
<msporny> [27]http://en.wikipedia.org/wiki/Percent-encoding
[27] http://en.wikipedia.org/wiki/Percent-encoding
Mark: every time I look at the URI spec I find it allows more
characters than I expected
... this discussion is pretty much the same discussion the @xmlns
folk had to go through
Manu: we could require that reserved characters must be %-encoded
... but that makes everything harder
Mark: and we'd have to avoid a requirement to double-encode
... we need a non-reserved character
Shane: good luck with that!
... remember that in the case of CURIE it's a IRI
... so even a bigger set of non-reserved character
... the only reserved character is space
... even schemalocation cheated by not using '=' or ':'; they just
use alternation
... the problem with alternation is that we can't do anything clever
with default or absent prefixes
... but maybe we don't need such rules
<msporny> prefix="a=b x=y"
<ShaneM> wow.... we already have this problem!
Mark: if we needed @prefix on every element then perhaps we might go
with [the '=' syntax]
<ShaneM> xmlns:foo="URI" what happens if URI contains a quotation
mark?
Mark: but perhaps we don't need that flexibility; be more
restrictive
... put everything in the head or having a predicate indicating a
prefix mapping
Ralhp: predicate as in RDF predicate?
Mark: yes
<ShaneM> <meta rel="prefix" name="foo" resource="URI" />
Mark: however I didn't like that syntax as it puts meta information
in the same graph as 'ordinary' information, which feels wrong
... I'm looking for something that is "cut-and-paste reliable"
Ralph: Creative Commons would not accept restrictions on where
mappings can be declared
Shane: separate two issues; 1. can we provide an alternative to
@xmlns that would be acceptable beyond the XML community and 2. how
do we make it easier for our constituents to use RDFa in easier ways
... we've talked about having external documents that declare
prefixes
... perhaps even with some well-known prefix declarations
... maybe we'll make more progress by not trying to find a single
solution to these two objectives
Mark: so do we need a lot of flexibility?
... find just enough flexibility for the goals at hand
<ShaneM> We should try hard to NOT over-engineer this solution
without having the requirements in mind!
Manu: the second idea is that there's an @profile value that pulls
in external mapping declarations
Mark: 1 is the namespace thing and 2 is ease of authoring
Shane: consider CSS syntax as an example of going too far; e.g.
borders on table cells -- totally different behavior depending on
how many values are supplied
<markbirbeck> dc: url(xyz)
Mark: I've just thought of another syntax!
Ralph: and it may be that the @xmlns problem will go away
<markbirbeck> Continuing Shane's point, why not 'solve' this:
<markbirbeck> [28]http://wiki.creativecommons.org/CcREL
[28] http://wiki.creativecommons.org/CcREL
Mark: pick an example of something people will frequently want to
copy and paste; e.g. ccRel
... the simple example [in ccRel] is interesting
... it just says some other mechanism has defined the token
... consider the lengthier scenarios; what other ways are there to
address these?
Manu: any of our proposed syntaxes would handle these examples
fairly cleanly
<msporny> prefix="a = b x = y"
Ralph: yeah, it's the ugly corner cases like ',' in URIs that are a
problem
<msporny> prefix="a=b x=y"
Shane: even quote is already an issue
Manu: a simple state machine will handle the '=' syntax
<ShaneM> prefix="
<ShaneM> a = b
<ShaneM> x = y
<ShaneM> "
Manu: I see the argument for an extensible syntax that could support
every use case but I wonder if [that flexiblity] will ever be used
... we're trying to solve a very simple problem
Shane: Mark's desire to make this legible can easily be written
using the '=' syntax
<markbirbeck> Shane don't we do this: xmlns:a=""b""
Shane: we can easily deal with extra whitespace
<markbirbeck> a = [29]http://example.org?a=b
[29] http://example.org/?a=b
<ShaneM> (.*)\s*=\s*(.*?)\s+
<markbirbeck> prefix="a = [30]http://example.org?a=b&c=d"
[30] http://example.org/?a=b&c=d
Manu: I'm leaning toward preferring this solution
... straightforward and easy to implement
<ShaneM> actually - can't use \s... need [\s\r\n]
Manu: don't think there's much danger of authors confusing the
syntax in the markup
next meeting: 2 weeks (April 16)
[adjourned]
<ShaneM> (.*)[\s\r\n]*=[\s\r\n]*(.*?)[\s\r\n]+
Summary of Action Items
[PENDING] ACTION: Ben to put up information on "how to write RDFa"
with screencast possibly and instructions on bookmarklet. [recorded
in [31]http://www.w3.org/2008/11/06-rdfa-minutes.html#action12]
[PENDING] ACTION: Jeremy to demonstrate GRDDL with XHTML/RDFa once
the NS URI is set up. [recorded in
[32]http://www.w3.org/2008/09/11-rdfa-minutes.html#action03]
[PENDING] ACTION: Manu to write summary for Semantic Web Use Cases
for Ivan. [recorded in
[33]http://www.w3.org/2008/09/11-rdfa-minutes.html#action09]
[PENDING] ACTION: Mark to send Ben ubiquity related wizard stuff
[recorded in
[34]http://www.w3.org/2008/11/20-rdfa-minutes.html#action11]
[PENDING] ACTION: Mark create base wizard suitable for cloning
[recorded in
[35]http://www.w3.org/2008/09/11-rdfa-minutes.html#action12]
[PENDING] ACTION: Mark write foaf examples for wiki [recorded in
[36]http://www.w3.org/2008/09/11-rdfa-minutes.html#action13]
[PENDING] ACTION: Michael to create 'RDFa for uF users' on RDFa Wiki
[recorded in
[37]http://www.w3.org/2008/09/11-rdfa-minutes.html#action14]
[PENDING] ACTION: Ralph or Steven fix the .htaccess for the XHTML
namespace [recorded in
[38]http://www.w3.org/2009/01/08-rdfa-minutes.html#action01]
[PENDING] ACTION: Ralph think about RSS+RDFa [recorded in
[39]http://www.w3.org/2008/09/11-rdfa-minutes.html#action15]
[31] http://www.w3.org/2008/11/06-rdfa-minutes.html#action12
[32] http://www.w3.org/2008/09/11-rdfa-minutes.html#action03
[33] http://www.w3.org/2008/09/11-rdfa-minutes.html#action09
[34] http://www.w3.org/2008/11/20-rdfa-minutes.html#action11
[35] http://www.w3.org/2008/09/11-rdfa-minutes.html#action12
[36] http://www.w3.org/2008/09/11-rdfa-minutes.html#action13
[37] http://www.w3.org/2008/09/11-rdfa-minutes.html#action14
[38] http://www.w3.org/2009/01/08-rdfa-minutes.html#action01
[39] http://www.w3.org/2008/09/11-rdfa-minutes.html#action15
[DONE] ACTION: Manu to look at
[40]http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2008D
ec/0037.html about resolving relative URIs [recorded in
[41]http://www.w3.org/2009/01/08-rdfa-minutes.html#action15]
[DONE] ACTION: Mark to review reasoning on setting explicit about=""
on HEAD and BODY [recorded in
[42]http://www.w3.org/2008/12/18-rdfa-irc]
[40] http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2008Dec/0037.html
[41] http://www.w3.org/2009/01/08-rdfa-minutes.html#action15
[42] http://www.w3.org/2008/12/18-rdfa-irc
[End of minutes]
______________________________________________________
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Received on Thursday, 2 April 2009 16:28:35 UTC