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JSON-LD Telecon Minutes for 2011-11-01

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Tue, 01 Nov 2011 13:29:52 -0400
Message-ID: <4EB02C90.1060003@digitalbazaar.com>
To: Linked JSON <public-linked-json@w3.org>
Many thanks to Tom for scribing! The minutes for today's call are now
available here:

http://json-ld.org/minutes/2011-11-01/

Full text of the discussion follows, as well as a link to the complete
audio transcript:

JSON-LD Community Group Telecon
Minutes for 2011-11-01
Agenda:
    http://lists.w3.org/Archives/Public/public-linked-json/2011Oct/0096.html
Chair:
    Manu Sporny
Scribe:
    Thomas Steiner
Present:
    Thomas Steiner, Manu Sporny, Markus Lanthaler, Gregg Kellogg,
    Niklas Lindström, David I. Lehn

Thomas Steiner is scribing.

Topic: ISSUE-37: Clarify prefix expansion

Manu Sporny: https://github.com/json-ld/json-ld.org/issues/37
Manu Sporny:  This was been mostly discussed via e-mail
Manu Sporny:  You split on a colon and attempt to expand the
    first item returned based on entries in the @context.
Markus Lanthaler:  nothing else needs to be added to the spec?
Manu Sporny:  only thing we need to do: make sure we add some
    text to the spec and detail the spec
Gregg Kellogg:  I'll take that action

ACTION: Gregg to add language to the JSON-LD spec, clarifying prefix 
expansion.

Manu Sporny:  Anything else we need to clarify?

Topic: ISSUE-38: Prefix location clarification

Manu Sporny: https://github.com/json-ld/json-ld.org/issues/38
Markus Lanthaler:  most of this has been addressed, but needs to
    be in the syntax doc
Manu Sporny:  slight bit of miscommunication on the list
Manu Sporny:  not clear in the current spec where prefixes are
    allowed
Manu Sporny:  answer is: anywhere there is an IRI
Markus Lanthaler:  except for in the top-level of the @context
Manu Sporny:  correct
Manu Sporny:  not allowed in the top level of the @context
Gregg Kellogg: Having CURIEs in the @context is the topic of
    current discussion
Manu Sporny:  Gregg, are you ok with that?
Gregg Kellogg:  we use curies in the @coerce section
Gregg Kellogg:  in the prefixes, IRIs must be spelled out
Gregg Kellogg:  Niklas might have different ideas
Niklas Lindström:  no, I agree
Niklas Lindström:  I would be open to allow curies everywhere in
    @context
Manu Sporny:  the only objection would be that we don't want too
    many ways for people to hang themselves
Manu Sporny:  we don't want to assume that someone loads the
    entire doc and processes it. we rather expect people to treat it
    as a stream in some cases.
Manu Sporny:  prefixes everywhere make it more complicated w/o
    adding great benefits
Niklas Lindström:  I understand, although, w/ coerce I feel it
    might not be possible to "stream-parse" it
Niklas Lindström:  I feel it's too complex to parse at once
Manu Sporny:  the processors would end up storing the key value
    pairs
Manu Sporny:  in the worst case you'd have to process the entire
    doc
Manu Sporny:  we don't want to lose that simplicity right now
Niklas Lindström:  will people use the context to create full
    RDF?
Manu Sporny:  we don't know - good question
Manu Sporny:  maybe not full RDF, but they will process it in
    some way that is stream based
Manu Sporny:  maybe they are extracting some data that requires
    IRIs
Niklas Lindström:  I can see that, we need to weigh that vs. the
    option to use IRIs on the right hand side
Niklas Lindström:  it's quite difficult in certain implemetations
Manu Sporny:  you could still stream it if you had control over
    the publishing-side
Niklas Lindström:  you could put the unresolvable things in a
    queue... wouldn't know if things are unresolveable unless you
    have some heuristics
Niklas Lindström:  if you put the definitions of the prefixes
    first, implying you have control over the order, then people
    resolving over already resolved prefixes, wouldn't be a problem
Manu Sporny:  is it useful to have CURIEs on the right hand side
    then?
Manu Sporny:  typically prefix definitions use completely
    different URIs
Manu Sporny:  same for schema.org
Gregg Kellogg: If we do "prefix": {"@iri": "…", "@coerce":
    "xsd:date"}
Niklas Lindström:  I use like four or five different vocabs in my
    use case
Niklas Lindström:  I would like to make use of more compact
    prefixes
Manu Sporny:  is that a very strong need?
Niklas Lindström:  I could do without it
Niklas Lindström:  one thing: showed context to a colleague w/
    little RDF knowledge
Niklas Lindström:  used the json view plugin
Niklas Lindström:  made content navigation very nice
Manu Sporny:  would that be a counter argument?
Niklas Lindström:  the real counter argument is that it's less
    complex
Niklas Lindström:  I would like to discuss it further
Niklas Lindström:  it would make things for me very much more
    compact
Manu Sporny:  let's put back to the mailing list for now
Manu Sporny:  I could live w/ either
Manu Sporny:  pro: makes readibility better
Manu Sporny:  con: doesn't enable any new technical use cases
Manu Sporny:  that's a semi weak counter argument, but that's the
    most convincing one for me.
Gregg Kellogg:  I can see the usefulness
Gregg Kellogg:  an alternative way to do it would be to allow the
    absence of an IRI and have the prefix to be inferred
Gregg Kellogg:  given we can have multiple contexts, we could
    have the IRIs be inferred
Niklas Lindström:  hey, that's really interesting
Niklas Lindström:  using vocab for that is quite useful
Manu Sporny:  general consensus is: it's interesting - don't put
    it in yet, discuss further on mailing list.
Manu Sporny:  we can always leave it out in the first version,
    and add it later - it's a forwards-compatible change
Manu Sporny:  no time pressure to decide on this
Manu Sporny:  we can just let people do implementations, and wait
Niklas Lindström:  I agree
Manu Sporny:  let's move on, then
Niklas Lindström:  we might have to rediscuss were CURIEs are
    allowed
Manu Sporny:  looking back at the issue-38
Manu Sporny:  people have to be careful not to expand common
    prefixes like ftp:, or http:
Gregg Kellogg: If a prefix is defined and the key/value is
    expanded, it is also determined to be an IRI
Manu Sporny:  if there is a term specified, we check it in the
    prefix map
Manu Sporny:  doing anything more than that complicates the rules
    I think
Manu Sporny:  any feelings?
Niklas Lindström:  I used to have troubles, but I think now it is
    a good way to go
Niklas Lindström:  one question regarding terms vs. prefixes
Manu Sporny:  they are the same thing
Manu Sporny:  if there is a colon, you take the bit before the
    colon and expand
Markus Lanthaler:
    http://json-ld.org/spec/latest/json-ld-api/#iri-expansion is now
    clear when terms/prefixes are expanded
Manu Sporny:  you have to say how you expand
Niklas Lindström: TermOrCURIEorIRI
Gregg Kellogg:  I think in my recent revision I defined prefixes
    and terms as just "terms"
Gregg Kellogg:  when you always divide on colon, and take the
    first part of that - you just try expanding that and that's all
    you have to do.
Manu Sporny:  ok, that makes perfect sense
Manu Sporny:  anything that simplifies is great
Niklas Lindström: does this TermOrCURIEorIRI rule also implied
    for @coerce: @iri? I believe it is - yes it is.
Manu Sporny:  Niklas wanted to allow prefixes in @coerce
Markus Lanthaler:  by the data section I meant the main content
    of the document
Manu Sporny:  whenever the property is supposed to be an IRI, you
    do term processing
Markus Lanthaler:  do we say somewhere say that terms can't
    contain colons
Gregg Kellogg:  I think we say that they are NCNAMEs
Manu Sporny:  not sure
Manu Sporny:  thats a corner case
Niklas Lindström:  the way this works has to be aligned with how
    people should use @base
Niklas Lindström: './whatever' instead of 'whatever' - otherwise,
    you could accidentally expand what was meant to be an relative
    IRI as a term.

ACTION: Gregg to define term (and other 'terms') more formally within 
syntax spec.

Manu Sporny:  I don't know how I feel about that. if you're using
    base, you can shoot yourself in the foot
Niklas Lindström: or something "./curie:like"
Manu Sporny:  wondering if @base should be expanded first, no,
    that doesn't work... you have to do term processing first
Niklas Lindström:  colons are allowed in segments of IRIs
Niklas Lindström:  if you use @base, you have to know what you're
    doing
Manu Sporny:  might be a best practice to use dot slash

ACTION: Gregg to add as best practice, relative IRIs should begin with 
"./" or "#" or "/"


Topic: ISSUE-35: JSON Vocabulary / Data Round-tripping

Manu Sporny: https://github.com/json-ld/json-ld.org/issues/35
Manu Sporny:  Markus suggested that we create a JSON-LD
    vocabulary
Manu Sporny:  the reason presented would be that we could do
    roundtripping
Manu Sporny:  we do this so that the data roundtrips well from
    serializing to deserializing
Manu Sporny:  for converting to native types
Manu Sporny:  doubles will almost always be lossy because of the
    way JSON parsers are implemented
Manu Sporny:  the double that you publish will be different than
    the double in C/C++
Manu Sporny:  has to do with what happens with the number when
    you process the JSON doc
Niklas Lindström:  I think I follow
Niklas Lindström:  if you use coerce rules, than the context
    should ensure that
Manu Sporny:  the translation is not guaranteed to happen safely
Manu Sporny:  even if we create a JSON vocab, it doesn't address
    the issue of data round-tripping
Markus Lanthaler:  but it moves it to the implementations - away
    from the spec
Markus Lanthaler:  a boolean could be 1, and 0
Markus Lanthaler:  I don't expect JSON developers to look at the
    xml XSD schema
Manu Sporny:  let's assume we publish jsonld:number, no one else
    besides us is gonna use it
Manu Sporny:  we would create a parallel data space to
    xsd:integer and xsd:double and xsd:decimal
Manu Sporny:  that the range of a type is bigger, does not mean
    we can't use it
Manu Sporny:  everything that JSON can express fits in XSD value
    space
Manu Sporny:  Markus, do any of these arguments convince you?
Markus Lanthaler:  two double values might be different when
    compared in a triple store
Markus Lanthaler:  if you retrieve a JSON-LD doc from somewhere,
    then store it, then retrieve another one, the reretrieve the
    previously saved one, then the values might not be equal
Manu Sporny:  I disagree
Niklas Lindström:  when we convert to JSON, we try to use the
    most convenient JSON view
Niklas Lindström:  is that the problem?
Manu Sporny:  correct
Manu Sporny:  there are 2 parallel issues: one is losing the
    lexical space, the other is native language data representation
    for doubles
David I. Lehn: handling of native doubles in JSON is just going
    to be potentially lossy due to JSON implementation details. not
    much we can do about that. handling strings coerced asxsd:double
    would be an alternative if you require more strict behavior.
Manu Sporny:  ISO specifies how to convert doubles, I believe
David I. Lehn: i can't remember why we picked %1.6e. I think I
    might have picked that for no particular reason. I forget though.
    :)
Manu Sporny:  none of the other data types are lossy, except for
    doubles
Manu Sporny:  if we follow the native ISO spec, then we are fine
    because it specifies string representation for a double value - I
    think.
Manu Sporny:  If ISO doesn't specify it, we could use the native
    JSON represenation and add a warning to the spec that the
    conversion may be lossy
Niklas Lindström:  wanted to agree that this is excellent
    handling of the problem
Niklas Lindström:  if they want exactness, they can use the
    string represenation w/ @datatype
David I. Lehn: people are going to get bitten by this so
    documentation is our only hope. I see people doing things like
    using native doubles and signing a serialized stream and it fails
    between implementations.
Markus Lanthaler:  when someone creates a json-ld doc, the double
    doesn't have to be in ISO format
Manu Sporny:  they can use whatever native json way
Markus Lanthaler:  if I want to compare, I have to normalize
    first
Niklas Lindström: .. So, something like this? .. real json
    numbers are passed into and out of json accompanied by @datatype
    (or @coerce) *and* expressed lexically according to the JSON-LD
    datatype lexical canonicalization
Manu Sporny:  that's correct
Manu Sporny:  also, you should never do double equality
    comparsions - recipe for disaster
Manu Sporny:  if you want to be on the safe side, use strings w/
    @datatype
Manu Sporny:  in the spec, does it say decimal or double?
Markus Lanthaler:  it says "number"
Markus Lanthaler: http://www.ietf.org/rfc/rfc4627
Manu Sporny:  xsd:double is the only thing we can do automatic
    typing on
Manu Sporny:  the machine-level representation will almost always
    be a double
Manu Sporny:  anything that has a dot or an 'e' (exponent) in it,
    will be a double in json-ld when you normalize
Niklas Lindström: http://www.w3.org/TR/turtle/#abbrev
Niklas Lindström: to sum up my last bit: 1) ensure we know what
    xsd datatype (different) json numbers are automatically
    represented as, 2) define a canonical lexical representation for
    each xsd number type
Niklas Lindström: #2 will be used both for automatically
    interpreted json numbers, and for once explicitly cast by either
    @datatype or @coerce

-- manu

-- 
Manu Sporny (skype: msporny, twitter: manusporny)
President/CEO - Digital Bazaar, Inc.
Standardizing Payment Links
http://manu.sporny.org/2011/payment-links/
Received on Tuesday, 1 November 2011 17:30:31 GMT

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