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Re: JSON-LD Telecon Minutes for 2013-07-02

From: David Booth <david@dbooth.org>
Date: Thu, 04 Jul 2013 00:03:49 -0400
Message-ID: <51D4F425.2020007@dbooth.org>
To: Pat Hayes <phayes@ihmc.us>
CC: Robert Sanderson <azaroth42@gmail.com>, Niklas Lindström <lindstream@gmail.com>, Linked JSON <public-linked-json@w3.org>, RDF WG <public-rdf-wg@w3.org>, public-openannotation <public-openannotation@w3.org>
On 07/03/2013 11:05 PM, Pat Hayes wrote:
> On Jul 3, 2013, at 2:55 PM, Robert Sanderson wrote:
>> I would be very interested to hear Pat's take on the matter, but
>> this does appear to be a valid concern with the reuse of
>> owl:sameAs. It seems that we're back to minting a new predicate to
>> link the resource and the head node of the list?
> You could do that, and it might be operationally a smart thing to do
> (see below). But David's worry will still apply to it. GIven what you
> want it to mean, its actual *semantics* are going to be the same as
> that of owl:sameAs, viz. that it means "=".

But in this case they really don't need the semantics to be the same as 
owl:sameAs semantics, even if they did describe it that way.  All they 
really need is to link the two nodes in a recognizable way.


> And given that semantics,
> it will in fact be logically valid to substitute its subject term for
> its object term. You can of course say that you don't want to allow
> this, but it will be *semantically* valid as a logical entailment.
> And you can *say* that you don't want the owl:SameAs substitutions to
> be performed on lists. On the other hand, this "saying" might have
> more bite, as it were, if you say it about a term that you own and
> whose meaning is defined in your documents (that its root IRI will
> link back to, in the great emerging LD tradition :-)
> Pat
> PS. BTW, don't ask the RDF WG to add some kind of rdf:sameAs to RDF.
> They won't do it. The established usage in the RDF world is to use
> owl:sameAs.
>> Rob
>> On Wed, Jul 3, 2013 at 1:47 PM, Niklas Lindström
>> <lindstream@gmail.com> wrote: Thanks David,
>> This worry was fleeting in the back of my mind as well, but I
>> didn't really express it.
>> It is also part of why I've been reluctant to proceed with the
>> otherwise fairly low-hanging fruit of extending JSON-LD to support
>> identifying and making statements about the front of an RDF list
>> (by simply allowing '@id' and other terms in an object representing
>> a literal list – i.e. an object using the '@list' key).
>> (.. Not to mention that this would take us closer to asking why we
>> can't do that for literals as well.. And then eventually discuss
>> equating '@value' and 'rdf:value'.. Not that I am theoretically
>> against such an evolution of RDF (that could solve the troublesome
>> "literals as subjects" debate, render SKOS-XL obsolete, and even
>> improve text search in SPARQL). But that would be nothing short of
>> a RDF 2.0 endeavour. Which is way beyond this..)
>> Cheers, Niklas
>> On Wed, Jul 3, 2013 at 8:40 PM, David Booth <david@dbooth.org>
>> wrote: Hi Rob,
>> The owl:sameAs solution does have the right semantics, and it has
>> the benefit of using a standard term.   But I'm afraid there may be
>> a downside as well, and I'm copying Pat to get his take on it.
>> Normally when you have:
>> <http://example/foo> owl:sameAs _:b1 .
>> in a graph, the blank node can be completely eliminated from the
>> graph and replaced by <http://example/foo>, because the semantics
>> of a blank node merely indicates the *existence* of a resource, but
>> the owl:sameAs assertion gives a concrete identity
>> <http://example/foo> to that resource.  But in your case, you want
>> to *avoid* having that blank node eliminated.  Thus, there could be
>> some risk that smart software that attempts to eliminate
>> unnecessary nodes and assertions (such as by making the graph
>> "lean")
>> https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-mt/index.html#dfn-lean
may eliminate the blank node triple that the Turtle serializer would 
need for serializing back to the original list syntax.
>> In other words, if the original graph said:
>> ... _:b1 a rdf:List . _:b1 rdf:first :s1 . ...
>> and you used owl:sameAs as above, then by owl:sameAs entailment we
>> would have:
>> ... _:b1 a rdf:List . <http://example/foo> a rdf:List . _:b1
>> rdf:first :s1 . <http://example/foo> rdf:first :s1 . ...
>> and if that were made lean then it would become:
>> ... <http://example/foo> a rdf:List . <http://example/foo>
>> rdf:first :s1 . ...
>> which would not serialize back to the original Turtle list ( :s1
>> ... ).
>> David
>> On 07/03/2013 11:15 AM, Robert Sanderson wrote:
>> Dear all,
>> TL;DR version:  I think that owl:sameAs is a great solution for
>> the predicate.
>> Thank you for the discussion!
>> The primary use case for lists with identity (and other
>> properties, potentially) in Open Annotation is to have an ordered
>> workflow for selecting the correct part of a document. For example,
>> EPub documents are just zip files with HTML and other resources
>> packed inside them, so it would be beneficial to reuse the methods
>> for selecting the correct segment of a resource on the web with the
>> resources inside the EPub, but first the file within the zip must
>> be selected.
>> Thus we would want:
>> <target1> a oa:SpecificResource ; oa:hasSelector <list1> ;
>> oa:hasSource <epub1> .
>> <list1> a oa:List, rdf:List ; rdf:isList (<FileSelector>,
>> <TextSelector>) . // Or something similar here
>> <FileSelector> a idpf:EpubFileSelector ; rdf:value "/chapter1.html"
>> .
>> <TextSelector> a oa:TextQuoteSelector ; oa:prefix "bit before the
>> segment" oa:exact "The text of the annotated segment" oa:suffix
>> "bit after the segment"
>> The relevant part of the specification is:
>> http://www.openannotation.org/spec/core/multiplicity.html#List (and
>> you'll see the long red editor's note!)
>> I think that Pat's suggestion of owl:sameAs is very appropriate.
>> It works in the different syntaxes and has the semantics that the
>> resources are the same -- in the case above the blank node that has
>> first of <FileSelector> and the resource <list1>.
>> The other options discussed were rdf:value, which is extremely
>> fuzzy and in JSON-LD context you couldn't assert that it always had
>> a list as its object if it was also used with a literal. In which
>> case it would result in multiple rdf:value predicates, each with
>> one of the list items as object. That led to discussing a new
>> predicate, such as listItems, listValue, isList, or similar.  This
>> would have the implication that the blank node and the main
>> identified resource were different resources, as compared to the
>> proposal of owl:sameAs which would mean they were the same
>> resource.
>> Rob
>> On Wed, Jul 3, 2013 at 12:30 AM, Pat Hayes <phayes@ihmc.us
>> <mailto:phayes@ihmc.us>> wrote:
>> On Jul 2, 2013, at 11:38 PM, David Booth wrote:
>>> On 07/03/2013 12:07 AM, Pat Hayes wrote:
>>>> On Jul 2, 2013, at 12:40 PM, Manu Sporny wrote:
>>>>> Thanks to Niklas for scribing. The minutes from this week's
>>>>> telecon are now available.
>>>>> http://json-ld.org/minutes/2013-07-02/
>>>>> Full text of the discussion follows including a link to the
>>>>> audio transcript:
>>>>> -------------------------------------------------------------------
>>> JSON-LD Community Group Telecon Minutes for 2013-07-02
>>>>> Agenda:
>> http://lists.w3.org/Archives/Public/public-linked-json/2013Jul/0000.html
>>> Topics:
>>>>> 1. Assigning Properties to Lists 2. GSoC update 3. JSON-LD /
>>>>> RDF Alignment 4. Lists in the JSON and RDF data models 5.
>>>>> Default interpretation of JSON arrays Resolutions: 1. Create
>>>>> an issue in the RDF WG to formalize a way to express lists
>>>>> that need to be identified with a URL and annotated using
>>>>> properties.
>>>> If I understand this correctly, this can be done in RDF
>>>> already. For example, the list [ x:a, x:b, 27 ] identified by
>>>> the URI ex:thisList and possessing the property x:prop with
>>>> value x:value is
>> described by
>>>> this RDF:
>>>> ex:thisList rdf:type rdf:List . ex:thisList rdf:first x:a .
>>>> ex:thisLIst rdf:rest _:1 . _:1 rdf:first x:b . _:1 rdf:rest
>>>> _:2
>> . _:2
>>>> rdf:first "27"^^xsd:number . _:2 rdf:rest rdf:nil .
>>>> ex:thisLIst x:prop x:value .
>>> If I have understood the issue properly, the reason for raising
>>> this issue in the RDF working group is that this is not
>>> necessarily an advisable usage pattern for the RDF list
>> vocabulary, because such a list cannot be serialized using
>> Turtle's list syntax: (x:a x:b 27).
>> Yes, you are right, and I confess I had never noticed this
>> limitation of Turtle previously. OK, let me change the RDF to the
>> following, keeping the list bnodes but using owl:sameAs. (You can
>> of course use some other property indicating equality if y'all
>> prefer.):
>> ex:thisLIst rdf:type rdf:List . ex:thisLIst x:prop x:value .
>> ex:thisList owl:sameAs _:3 . _:3 rdf:first x:a . _:3 rdf:rest _:1
>> . _:1 rdf:rest _:2 . _:2 rdf:first "27"^^xsd:number . _:2 rdf:rest
>> rdf:nil .
>> Or, in Turtle:
>> ex:thisList rdf:type rdf:List ; x:prop x:value ; owl:sameAs (x:a ,
>> x:b, 27 ) .
>> and you could probably omit the first triple, or even introduce
>> your own category of JSON-lists and say it is one of those,
>> instead, if that would help with triggering appropriate
>> translations into other formats (or to distinguish these from eg
>> RDF lists used to encode OWL syntax.)
>>> It falls into a  similar category as other uncommon uses of the
>> RDF List vocabulary:...
>> ...no, it doesn't. See remark below.
>> Pat
>>> other uncommon uses of the RDF List vocabulary:
>>> http://www.w3.org/TR/rdf-schema/#ch_collectionvocab [[ Note: RDFS
>>> does not require that there be only one first element
>> of a list-like structure, or even that a list-like structure have
>> a first element.
>>> ]]
>>> While not prohibited by RDF, such uncommon uses of the RDF list
>> vocabulary are certainly seen by some as being somewhat
>> anti-social. Thus, the question is whether such uses should be
>> *encouraged*.
>>> David
>>>> Pat
>>>>> Chair: Manu Sporny Scribe: Niklas Lindström Present: Niklas
>>>>> Lindström, Robert Sanderson, Markus Lanthaler, Manu Sporny,
>>>>> David Booth, David I. Lehn, Vikash Agrawal Audio:
>>>>> http://json-ld.org/minutes/2013-07-02/audio.ogg
>>>>> Niklas Lindström is scribing.
>>>>> Topic: Assigning Properties to Lists
>>>>> Markus Lanthaler:
>>>>> https://github.com/json-ld/json-ld.org/issues/75 Robert
>>>>> Sanderson:  we'd very much like to give rdf:Lists identity,
>>>>> so that they can be referenced from multiple graphs. Also to
>>>>> describe them with other properties ... in openannotation, we
>>>>> need lists to define a selector which determines which part
>>>>> is annotated ... for instance, which piece of a text is
>>>>> annotated, with "before" and "after" also recorded (most
>>>>> clients work like that) ... Futhermore, IDPF has agreed to
>>>>> use openannotation for all EPub books ... EPubs, being zip
>>>>> files with a bunch of files ... To define a selector here
>>>>> (take the EPub, select a file, then a part in there) ... So
>>>>> we don't want to reproduce every single selector mechanism.
>>>>> Thus, an ordered list of two selectors would be neeeded. ...
>>>>> We thus need to identify lists, so that we can reuse these
>>>>> selectors in multiple statements. ... I.e. a person wants to
>>>>> disagree with a specific annotation, or place being
>>>>> annotated. ... Furthermore, we have the order of multiple
>>>>> targets, e..g. "the first passage on page three, is derived
>>>>> from the second passage on page five" ... Not as essential,
>>>>> since it's not really machine actionable ... Another project
>>>>> using lists is Shared Canvas ... We'd very much like to use
>>>>> JSON-LD there too, for selecting pages, using a list of pages
>>>>> and so forth ... For this, we took the "list items" approach;
>>>>> the list doesn't need to be referenced directly. Markus
>>>>> Lanthaler: robert, do you have the link of an example at
>>>>> hand? ... But it might be nice to have this standardized, so
>>>>> people don't reinvent list items all the time. ... at the
>>>>> mailing list and also the OA community meeting in Europe, we
>>>>> agreed that we don't want to change the model to accomodate
>>>>> different syntaxes ... We want to recommend JSON-LD Manu
>>>>> Sporny: what's the timeline for these needs / when would the
>>>>> WG close Robert Sanderson:  at the moment, the CG is in an
>>>>> implementation phase. We need to dicuss with Ivan, but we
>>>>> hope to move from CG to WG next year Manu Sporny:  we're very
>>>>> close to CR in JSON-LD. If we'd add his feature in, it would
>>>>> put us back for many months. Could we add this for JSON-LD
>>>>> 1.1? ... If we think we can put the feature in, I think we
>>>>> can easily convince implementers to add it. If we add it to
>>>>> the test suite, other implementers would add it. ... So for
>>>>> practical purposes, we aim for it to be added within a year
>>>>> or so. Robert Sanderson:  Yes, that approach could work for
>>>>> us. Given that your'e much further ahead. It's not our
>>>>> prefered option, since for implementations, it might be
>>>>> unpredictable. ... Also, changing this for OA now is much
>>>>> easier than when in a WG ... I don't believe anyone has
>>>>> implemented it yet, but IDPF needs this to be implementable
>>>>> Manu Sporny:  so we may put it in jSON-LD 1.1 Niklas
>>>>> Lindström:  First thing, as far as I know, Turtle doesn't
>>>>> support this syntax either. Given that you have a shorthand
>>>>> in Turtle.... actually, none of the formats in RDF/XML and
>>>>> Turtle support this sort of list syntax. [scribe assist by
>>>>> Manu Sporny] Markus Lanthaler: niklasl, AFAICT they currently
>>>>> set rdf:rest to a Turtle list Niklas Lindström:  Have you
>>>>> discussed that as well? Am I missing something? [scribe
>>>>> assist by Manu Sporny] Robert Sanderson:  No, I don't think
>>>>> you missed anything. [scribe assist by Manu Sporny] Robert
>>>>> Sanderson:  The identity is easier in RDF/XML - you have the
>>>>> property for the URI. [scribe assist by Manu Sporny] Robert
>>>>> Sanderson:  We did consider the other serializations, it's
>>>>> not a ubiquitous feature, but it would be nice to have in
>>>>> JSON-LD. [scribe assist by Manu Sporny] Niklas Lindström:
>>>>> Right, the main argument when we had the issue, even though
>>>>> it's in the Primer that says there is nothing preventing
>>>>> lists from being described, multiple start properties, etc.
>>>>> None of the core syntaxes allow it, it's not intended to be
>>>>> used like that. [scribe assist by Manu Sporny] Niklas
>>>>> Lindström:  They're supposed to be used as syntactic
>>>>> constructs.... model-wise, they're not really a part of RDF.
>> That is not correct. Collections were intended to be an integral
>> part of RDF. They were used by OWL as a syntactic device for
>> encoding OWL syntax in RDF, making them unavailable inside OWL,
>> but that is an OWL/RDF issue. (IMO, with hindsight, this was a
>> serious mistake in designing the OWL/RDF layering. But I was there
>> at the time and didn't see the danger myself, so mia culpa.)
>>>>> [scribe assist by Manu Sporny] Niklas Lindström:  If this is
>>>>> supported in JSON-LD, it would be a lot easier to deviate
>>>>> from the recommended usage pattern.... also making it harder
>>>>> for a future RDF spec, who wants to add lists as a native
>>>>> part of the model [scribe assist by Manu Sporny] Niklas
>>>>> Lindström:  You can still use rdf:first / rdf:next
>>>>> explicitly today. [scribe assist by Manu Sporny] Robert
>>>>> Sanderson:  I agree. The notion of order in a graph is always
>>>>> problematic. Not the common method to have a resource that is
>>>>> a list and has identity. [scribe assist by Manu Sporny]
>>>>> Robert Sanderson:  Maybe RDF COncepts 1.1 should discuss it.
>>>>> [scribe assist by Manu Sporny] David Booth:  Yeah, RDF WG
>>>>> should consider this. I agree with Niklas. It doesn't fit w/
>>>>> the usual list pattern. Important to consider implications.
>>>>> [scribe assist by Manu Sporny] ... Here's an example:
>>>>> http://www.openannotation.org/spec/core/multiplicity.html#List
>>> Robert Sanderson: That's it exactly, thanks Niklas1 Manu Sporny:
>>>>> any other thoughs on this? Markus Lanthaler:  it would make
>>>>> it hard to expect compaction to behave as predicted ... also,
>>>>> compaction might be more complex Manu Sporny:  Yes. We wanted
>>>>> to stay away from it since it might be a mine field in
>>>>> general. ... that said, there might be a case for this.
>>>>> Niklas Lindström:  Agree with Manu's point - there might be
>>>>> something new that's interesting here. I don't think we
>>>>> should do it w/o discussing implications. Algorithmic
>>>>> complexity for JSON-LD API and implementations. It might be
>>>>> almost as problematic as bnodes as predicates. It's possible
>>>>> to do this in raw RDF. It seems highly obvious that you can
>>>>> add ID in other properties. On the other hands you...
>>>>> [scribe assist by Manu Sporny] Manu Sporny: ...can do it w/
>>>>> literals. Niklas Lindström:  This borders on the syntactical
>>>>> collapse. [scribe assist by Manu Sporny] Markus Lanthaler:
>>>>> syntactically having a property carrying the actual list is
>>>>> nearly indistinguishable as the requested form (using "@list"
>>>>> as key) Robert Sanderson:  I agree. The easisest solution for
>>>>> everyone would be to have a "listItem" as a property. ... and
>>>>> for the RDF WG, it might be good to define a dedicated
>>>>> predicate for it. rdf:value is explicitly fuzzy, so you can't
>>>>> always expect a list. David Booth: Robert, would it be
>>>>> feasible to just wrap the list in another object, and attach
>>>>> the additional info to the wrapper object? (I apologize that
>>>>> I have not fully grokked the problem, so this suggestion may
>>>>> not be helpful.) ... It would be easier to sell changing the
>>>>> model if there was another predicate for this. Manu Sporny:
>>>>> so a specific vocabulary for lists would be beneficial in
>>>>> general, working in all syntaxes ... would that adress this
>>>>> issue? If we quickly create a list vocabulary? Robert
>>>>> Sanderson:  I think so. Not preferable duing the discussions
>>>>> we had, but the syntactic arguments may sway this position.
>>>>> ... A single, interoperable solution is preferable. Manu
>>>>> Sporny:  anyone objects to open issue 75, to continue this
>>>>> dicussion? Niklas Lindström:  I think we should try to have
>>>>> this as an RDF issue - it really would not come up if lists
>>>>> were core to the RDF model. It's a sore spot in RDF Concepts.
>>>>> I think we should push it over to the RDF WG immediately.
>>>>> It's arbitrary if we or OA try to push something forward, it
>>>>> won't solve the real problem.... not in rdf schema vocab.
>>>>> [scribe assist by Manu Sporny] Robert Sanderson: +1 to
>>>>> Niklas
>>>>> PROPOSAL: Create an issue in the RDF WG to formalize a way
>>>>> to express lists that need to be identified with a URL and
>>>>> annotated using properties.
>>>>> Manu Sporny: +1 David Booth: +1 Robert Sanderson: +1 Niklas
>>>>> Lindström: +1 could be someything like rdf:listValue David I.
>>>>> Lehn: +1 Markus Lanthaler: +1
>>>>> RESOLUTION: Create an issue in the RDF WG to formalize a way
>>>>> to express lists that need to be identified with a URL and
>>>>> annotated using properties.
>>>>> Topic: GSoC update
>>>>> Vikash Agrawal:  what's broken in the playground? Manu
>>>>> Sporny:  a bit weird ui paradigm when clicking on expanded
>>>>> form; headings for JSON-LD Context stay, but the input box
>>>>> disappears. Markus Lanthaler:
>>>>> http://www.markus-lanthaler.com/jsonld/playground/ Markus
>>>>> Lanthaler:  the headers stay but the inputs disappear.
>>>>> Previously headers were toggled off if input areas weren't
>>>>> applicable Manu Sporny:  play around a bit. I think the old
>>>>> way is better. There may be something even better, but right
>>>>> now, the problem is that something not used is still shown.
>>>>> Vikash Agrawal: this is bug 50 ... by this week, this should
>>>>> be done. Next week is a creator app. Markus Lanthaler: could
>>>>> we discuss these things on the mailing list or the issue
>>>>> tracker? Manu Sporny:  email danbri and gregg regarding a
>>>>> schema.org <http://schema.org> JSON-LD
>> context Markus Lanthaler:
>>>>> vikash, here's Sandro's schema.org <http://schema.org>
>>>>> context:
>>>>> http://www.w3.org/People/Sandro/schema-org-context.jsonld
>>>>> Markus Lanthaler: for the creator app, have a look at:
>>>>> http://schema-creator.org/
>>>>> Topic: JSON-LD / RDF Alignment
>>>>> Manu Sporny:
>>>>> http://lists.w3.org/Archives/Public/public-rdf-wg/2013Jun/0233.html
>>> Manu Sporny:  I went into the spec and tried to integrate what
>>> we
>>>>> have consensus on. ... see the email link above for a list
>>>>> of things. ... everything should be there except for
>>>>> skolemization David Booth:  I just found it, but I think it
>>>>> looks great (just some minor things) Manu Sporny:  would it
>>>>> adress the LC comment? David Booth:  It might. It's in the
>>>>> right direction. Manu Sporny:
>> http://json-ld.org/spec/ED/json-ld/20130630/diff-20130411.html#data-model
>>> Manu Sporny:  next, Peter's changes. Appendix A was changed to
>>>>> flat out say that JSON-LD uses an extended RDF model. ... we
>>>>> just say "Data Model", and that it's an extension of the RDF
>>>>> data model. Markus Lanthaler:
>>>>> http://lists.w3.org/Archives/Public/public-rdf-wg/2013Jul/0010.html
>>> ... we need to have a resonse from Peter on this.
>>>>> David Booth:  I'd expect it to be, to the extent that I can
>>>>> channel Peter. David Booth: Every node is an IRI , a blank
>>>>> node , a JSON-LD value , or a list . David Booth:
>>>>> restricting the literal space to JSON-LD values is a
>>>>> restriction rather than an extension to the RDF model. Robert
>>>>> Sanderson: Sorry, have to attend another call now, though
>>>>> would like to have stayed for the rest of the conversation.
>>>>> Thanks everyone for the discussion re lists. ... and I don't
>>>>> think that lists need to be mentioned there; they are just
>>>>> sugar. Markus Lanthaler: "A JSON-LD value is a string, a
>>>>> number, true or false, a typed value, or a language-tagged
>>>>> string." Markus Lanthaler: thanks for joining robert Manu
>>>>> Sporny:  on top, we extension the value space to json true
>>>>> and false, numbers and strings. David Booth: A JSON-LD value
>>>>> is a string , a number , true or false , a typed value , or a
>>>>> language-tagged string . David Booth:  it wasn't clear that
>>>>> those lined up with the corresponding RDF value space. Manu
>>>>> and David agree that the JSON number value space is more
>>>>> general. Manu Sporny:  different lexical spaces for booleans
>>>>> in xsd and json
>>>>> Topic: Lists in the JSON and RDF data models
>>>>> David Booth:  What about lists, aren't they the same as
>>>>> expressed in RDF? Manu Sporny:  not convinced that they are..
>>>>> ... we need to translate it to something in the data model.
>>>>> In RDF, it translates to the list properties. There is
>>>>> nothing in RDF concepts to point to. ... many just assumes
>>>>> that it's basically part of the data model, but it's formally
>>>>> not David Booth:  why not point to rdf schema? Manu Sporny:
>>>>> not part of the rdf data model. Niklas Lindström:  Yeah, just
>>>>> a comment. Could we correlate this RDF Concepts problem w/
>>>>> the suggestion wrt. list values. [scribe assist by Manu
>>>>> Sporny] David Booth: RDF lists: David Booth:
>>>>> http://www.w3.org/TR/rdf-schema/#ch_list Niklas Lindström:
>>>>> Clearly, lists are under-specified. [scribe assist by Manu
>>>>> Sporny] Niklas Lindström:  Maybe we should expand RDF
>>>>> Concepts that is present in the 2004 Primer and the Syntax
>>>>> that I scanned previously. [scribe assist by Manu Sporny]
>>>>> Manu Sporny:  but does rdf schema extend the rdf data model?
>>>>> David Booth:  no, just a convention which is using the rdf
>>>>> data model Markus Lanthaler: but's still just a vocabulary.
>>>>> In JSON-LD, we use [a keyword and] an array ... it's like a
>>>>> node type [just as literals] Manu Sporny: the JSON-LD data
>>>>> model does not talk about rdf:first and rdf:rest David Booth:
>>>>> I don't think any test cases needs to be changed by the way
>>>>> this is described. So it's just a question of how this
>>>>> concept is being described. At present, it's described as a
>>>>> difference. Manu Sporny:  True. We only change how you think
>>>>> about the data model. Manu Sporny:  if we make an argument
>>>>> about the difference between native JSON literals and RDF
>>>>> literals, we need to explain the difference of expressing
>>>>> lists as well. David Booth: I don't see the benefit as a
>>>>> difference, from an RDF perspective. Niklas Lindström:  I
>>>>> think I can answer re: benefit of having different model wrt.
>>>>> JSON lists and RDF lists. In JSON, there are arrays, those
>>>>> arrays represent repeated statements in RDF> [scribe assist
>>>>> by Manu Sporny] Niklas Lindström:  RDF people understands
>>>>> that intuitively. We mention @set because people that don't
>>>>> understand RDF, but do understand mathematical sets....
>>>>> ordered list is more popular than sets in programming.
>>>>> [scribe assist by Manu Sporny] Niklas Lindström:  We need a
>>>>> way to explain lists in JSON-LD, in the same way that we
>>>>> explain sets, and other things. Not in a way that introduces
>>>>> rdf:first and rdf:next. [scribe assist by Manu Sporny] David
>>>>> Booth: Bottom line: I do not see a need to call out lists as
>>>>> being a difference from the RDF model, but I'm okay with it
>>>>> being mentioned, in part because I'd like to push RDF to have
>>>>> native lists. Markus Lanthaler: manu, did you see
>>>>> http://lists.w3.org/Archives/Public/public-rdf-wg/2013Jul/0010.html
>>> already?
>>>>> Topic: Default interpretation of JSON arrays
>>>>> David Booth:  it seems strange to have @set (unordered) as
>>>>> the default ... in regular json, the default is ordered
>>>>> Markus Lanthaler:  We discussed this quite a bit in the
>>>>> beginning, the rationale was that the RDF that was generated
>>>>> would be unmanageable - lots of blank nodes, lots of
>>>>> rdf:first/rdf:rest, you couldn't work w/ the RDF anymore.
>>>>> [scribe assist by Manu Sporny] Markus Lanthaler:  we
>>>>> discussed it quite a bit in the beginning. The rationale we
>>>>> came up with is that the generated RDF would be very
>>>>> gruesome, using rdf lists for everything. ... hundreds of
>>>>> blank nodes for everything. Niklas Lindström:  Yeah, I agree.
>>>>> That's the rationale. While it's true that arrays in JSON are
>>>>> ordered in their nature, in all the JSON-LD examples, they
>>>>> are commonly only sets. There is no real order. JSON-LD is
>>>>> intended to be used w/ RDF properties, there are only a
>>>>> handful of common RDF properties - author, contributorList,
>>>>> propertyChainAction, where the order is semantic, it means
>>>>> something. [scribe assist by Manu Sporny] Niklas Lindström:
>>>>> In every other case, it's just a bundle of things. I think
>>>>> that's the better case - explicitly say order doesn't mean
>>>>> anything. The same thinking has obscured lots of things wrt.
>>>>> XML. You can rely on the order of the elements, not sure if
>>>>> you should. It's better to say that "you can't rely on the
>>>>> order", unless someone says so explicitly. [scribe assist by
>>>>> Manu Sporny] David Booth:  As a programmer, I'd use the exact
>>>>> opposite rationale. [scribe assist by Manu Sporny] David
>>>>> Booth: So if the default were changed to being ordered, then
>>>>> the examples would have to be changed to add @set? Markus
>>>>> Lanthaler: https://github.com/json-ld/json-ld.org/issues/12
>>>>> Niklas Lindström: We discussed whether we should do it in the
>>>>> @context, we could define @set to be the default. [scribe
>>>>> assist by Manu Sporny] Niklas Lindström:  I agree w/ David
>>>>> that as a programmer, you think like that. Unless you think
>>>>> otherwise. [scribe assist by Manu Sporny] David Booth:  There
>>>>> is also minimal changes going from JSON to JSON-LD. [scribe
>>>>> assist by Manu Sporny] Niklas Lindström: Datasets on the Web,
>>>>> you never know if the order is intentional or not. It's
>>>>> better to assume that it's not ordered. [scribe assist by
>>>>> Manu Sporny] Markus Lanthaler:  JSON-LD can already serialize
>>>>> the same data in so many ways already - remote contexts, you
>>>>> can't really interpret the data anymore by just looking at
>>>>> it. Maybe doing it in a processor flag, but not in the
>>>>> context. [scribe assist by Manu Sporny] Niklas Lindström:
>>>>> I'd like to be able to do this in the context. "@container":
>>>>> "@set" would be useful to me. [scribe assist by Manu Sporny]
>>>>> David Booth: Can we have a global way to indicate @set ?
>>>>> Niklas Lindström:  Yeah, but I could wait for this feature.
>>>>> [scribe assist by Manu Sporny] David Booth:  I'm worried
>>>>> about the element of surprise. It reverses the common
>>>>> expectation. Manu Sporny:  It has not come up as a real issue
>>>>> from anywere though. Markus Lanthaler:  Is there a use case
>>>>> for this? [scribe assist by Manu Sporny] Markus Lanthaler:
>>>>> In the majority of instances, the order is irrelevant David
>>>>> Booth:  yes, quite possible Manu Sporny:  a change could also
>>>>> backfire at this stage ... we could potentially have a
>>>>> JSON-LD 1.1, for e.g. this. David Booth: I think the best
>>>>> solution would be a simple global way to specify @set, and
>>>>> user get used to always doing that. Niklas Lindström:  I
>>>>> think that it can't fly from my point of view - given that
>>>>> for every case where I've seen order having meaning, it's
>>>>> always been a very specific technical reason. Implicitly
>>>>> ordered things as properties on the object. In every specific
>>>>> scenario where order is used.... [scribe missed] [scribe
>>>>> assist by Manu Sporny] Niklas Lindström:  check out
>>>>> schema.org
>> <http://schema.org>· only a handful
>>>>> where the meaning is explicitly ordered:
>>>>> http://www.w3.org/People/Sandro/schema-org-context.jsonld
>>>>> Niklas Lindström:  I might be open that it should be ordered,
>>>>> but not by default. [scribe assist by Manu Sporny]
>>>>> -- manu
>>>>> -- Manu Sporny (skype: msporny, twitter: manusporny, G+:
>>>>> +Manu Sporny) Founder/CEO - Digital Bazaar, Inc. blog:
>>>>> Meritora - Web payments commercial launch
>>>>> http://blog.meritora.com/launch/
>>>> ------------------------------------------------------------
>>>> IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St.
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>>>> (850)202 4440   fax FL 32502
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>> ------------------------------------------------------------ IHMC
>> (850)434 8903 or (650)494 3973 40 South Alcaniz St.
>> (850)202 4416   office Pensacola
>> (850)202 4440   fax FL 32502                              (850)291
>> 0667   mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
> ------------------------------------------------------------ IHMC
> (850)434 8903 or (650)494 3973 40 South Alcaniz St.
> (850)202 4416   office Pensacola                            (850)202
> 4440   fax FL 32502                              (850)291 0667
> mobile phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
Received on Thursday, 4 July 2013 04:04:19 UTC

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