Re: FPWD comment - literals, data types and language tags

Hi Ivan, Jeff,

Firstly, I agree wholeheartedly with Jeff's position that we shouldn't be
mixing up model and serialization ... but that's exactly what the
requirement is for string literal bodies.

The model requirement would be:  I want to embed a textual comment within
the annotation as the body.  That's precisely what the EmbeddedContent
resource does (and ContentAsText used to do).  Indeed, when the requirement
was brought up at the CSV WG (for example) the negative reaction was not to
the model, but to the serialization as a JSON object instead of a string.

The requirement to have language associated with a string is also perfectly
reasonable, and already accounted for.   The requirement to have format
associated with a string, ditto.  And the clincher is having both format
and language is not possible with literals in RDF, and must be done with a
resource.

So, if we want to not talk about serialization, that's fine, but the answer
is to get rid of string literals and have a single, coherent model for
embedded content.

If value was mapped to @value and language to @language, that would work
until someone wanted to associate a format with the content. And then it
would break spectacularly.

If we allowed language tagged and (separately) data-typed literals we would
have the following possible combinations all being legal that clients would
have to take into account:

"body": "string"
"body": {"@value": "string"}
"body": {"value": "string"}
"body": {"@value": "string", "@language": "en"}
"body": {"value": "string", "language": "en"}
"body": {"@value": "<b>string</b>", "@type": "rdf:HTML"}
"body": {"value": "<b>string</b>", "format": "text/html"}
// Not @value, @language, @type !
"body: {"value": "<b>string</b>", "language": "en", "format": "text/html"}

Are you SURE that is preferable to a single consistent model?  Do you
REALLY want us to have to explain that the @value/@language/@type
combination is not allowed because RDF (oh oh, warning bells!) doesn't
allow it and hence developers need to deal with lots of special cases?
That is the consequence of going down this route.

I am strongly against it.

Rob


On Sun, Dec 14, 2014 at 1:18 AM, Ivan Herman <ivan@w3.org> wrote:
>
> Jeff
>
> I think this can be mitigated, actually. We need again a JSON-LD expert
> but I would expect the @context to be able to map a "value" to "@value" and
> "language" to "@language", if we really do not want to impose the usage of
> "@" signs for special properties. Ie, we do not have a different JSON
> serialization.
>
> If this is so, then, in fact, we solve both issues. The JSON-LD idiom
>
> "body" : {"value": "hi", "language": "en"}
>
> would, in fact, be equivalent to
>
> "body" : {"@value": "hi", "@language": "en"}
>
> which means that the value of "body" is a language string, not a separate
> resource. Which is exactly what Antoine wants. In fact, this is one of the
> cases where the Turtle serialization is way more readable, because it would
> be
>
> <> oa:body "hi"@en .
>
> _If_ the @context cannot be used for the mapping above, then I fully agree
> with Jeff's reaction. We should then use the "@value" and "@en" terminology
> in JSON-LD (I do not think that would really create major issues of
> acceptance, frankly), and thereby avoid a duplication of concepts. As a
> bonus, we also solve Antoine's issue for free:-)
>
>
> Ivan
>
>
> > On 14 Dec 2014, at 04:05 , Young,Jeff (OR) <jyoung@OCLC.ORG> wrote:
> >
> > The serialization may look "the same" to human eyes, but here's the spec
> for JSON-LD:
> >
> > http://www.w3.org/TR/json-ld/#string-internationalization
> >
> > It would be a shame if Web Annotations invented another JSON
> serialization. What would that one be called?
> >
> >
> http://blog.ldodds.com/2010/12/02/rdf-and-json-a-clash-of-model-and-syntax/
> >
> > On Dec 13, 2014, at 8:21 PM, Robert Sanderson <azaroth42@gmail.com>
> wrote:
> >
> >>
> >> Hi Antoine, all,
> >>
> >> To me the only value of literal bodies is to enable a simple string.
> As soon as you add data types or language tags, the complexity and even
> serialization is the same as using a full resource, almost character for
> character:
> >>
> >> Language tagged string:
> >>     {"@value": "hi", "@language": "en"}
> >>
> >> Real (blank node) resource:
> >>     {"value": "hi", "language": "en"}
> >>
> >> The argument against always using a resource, and thereby enabling full
> OWL reasoning and a consistent model that respects the web architecture, is
> that people want to have only a string without anything else ... so that's
> all we allowed.
> >>
> >> As the model allows for language (and format and other metadata) to be
> associated with the body using the (preferred) resource method, and we
> don't want to create multiple ways to do the same thing, I'm against (as
> you might imagine) allowing language tagged literals.
> >>
> >> Rob
> >>
> >>
> >> On Sat, Dec 13, 2014 at 7:46 AM, Antoine Isaac <aisaac@few.vu.nl>
> wrote:
> >> Dear all,
> >>
> >> Congrats for the WD!
> >>
> >> I'm looking at it now, and I'm really happy with simple bodies.
> >> I am not so happy however with the fact that the spec does forbid the
> use of language tags on simple text bodies.
> >>
> >> In the OA community, several months ago, there was a discussion about
> XML-datatypes vs plain-literals-with-language-tags. As Rob reminded me in
> private mail:
> >> [
> >> The issue with datatypes and language tags is:
> >>
> >> * You can't have both at once in RDF, so we need to allow:
> >>     {"value": "hi", "language": "en", "format": "text/plain"}
> >>
> >> * In JSON-LD, the difference between a language tagged literal, and the
> resource is very confusing:
> >> "hi"@en is:  {"@value": "hi", "@language" : "en"}
> >> Whereas the blank node just drops the @s:   {"value": "hi", "language":
> "en"}
> >> If we allowed both patterns, we'd be losing any simplicity and
> understandability gains by having them at all.  So if there's more
> information than just the value, including format, language, creator, etc,
> then it has to be a resource following the web architecture.
> >>
> >> * If the body data type isn't fixed, you would end up with the same
> situation as language tags, just with @type and format.  So to prevent it
> we require it to be an xsd:string, which will serialize to just the string
> in JSON-LD compaction.
> >> ]
> >>
> >> At the time I accepted these arguments. But I think what convinced me
> then is that there were cases mentioned for literal bodies that would have
> a different (XML) datatype.
> >> Now the FPWD mentions only simple text bodies. So this makes the case
> for not using plain literals a lot weaker.
> >>
> >> If I was a fresh reader, it would puzzle me a lot to find the sentence
> >> "The string body MUST be an xsd:string and MUST NOT have a language
> associated with it."
> >> And as someone with a key interest in multilingual scenarios, I want to
> raise again the issue!
> >> In fact the current solution makes annotations-with-literals useless in
> many of the Europeana cases, so I'd rather see a very good case for not
> enabling language tags.
> >>
> >> Best regards,
> >>
> >> Antoine
> >>
> >>
> >>
> >> --
> >> Rob Sanderson
> >> Information Standards Advocate
> >> Digital Library Systems and Services
> >> Stanford, CA 94305
>
>
> ----
> Ivan Herman, W3C
> Digital Publishing Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> ORCID ID: http://orcid.org/0000-0003-0782-2704
>
>
>
>
>

-- 
Rob Sanderson
Information Standards Advocate
Digital Library Systems and Services
Stanford, CA 94305