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comments on the json-ld document

From: Ivan Herman <ivan@w3.org>
Date: Tue, 30 Aug 2011 19:02:12 +0200
Cc: public-linked-json@w3.org
Message-Id: <D6640C5D-8EE1-4FB7-87A4-40D56B695C38@w3.org>
To: Manu Sporny <msporny@digitalbazaar.com>, Gregg Kellogg <gregg@kellogg-assoc.com>
Manu, Gregg,

I finally sat down to read the JSON-LD document. Unfortunately, I did not find the time to go to the very end. I have got as far (but not included) section 5. Here are my comments...

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"It is designed to be able to express key-value pairs, RDF data, RDFa [RDFA-CORE] data, Microformats [MICROFORMATS] data, and Microdata [MICRODATA]"

But... there is no such thing as RDFa data. RDFa is simply a serialization of RDF data... So I do not understand what is meant here for RDFa.

The same comment holds for the item on targeted audience ("Software developers that want to encode Microformats, RDFa, or Microdata in a way that is cross-language compatible via JSON."

--------

"Linked Data is a set of documents, each containing a representation of a linked data graph"

Is the word 'document' really good here? Most people, when seeing this term, would consider a web page, or a PDF page... I would use 'resources' here.

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So what is the relationship of the semantic web and linked data? Section 2.4 says "The semantic web, just like the document-based web, uses IRIs for unambiguous identification." which then comes a little bit out of the blue...

--------

It is the first time I see the term "Web Vocabulary" (later in 2.4). Why not simply "Vocabulary"?

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In 2.4.1: I presume it is correct that a context document is not exactly the same as a JSON-LD document, though it looks the same...

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Third example in 3.1 seems to be misleading in the text. This is not a prefix...

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Beginning of 3.1, it says "In the example above, the key http://xmlns.com/foaf/0.1/name is interpreted as an IRI, as opposed to being interpreted as a string." What are the rules to turn this into an IRI instead of a string? Is it based on the regexp for URI-s? But, if those are used, then why needing a coersion rule for the similar functionality in case of objects?

------

I was looking for some precise rules on the where the definition of a @context would apply. I would expect something like "the rules in @context are valid in the enclosing object and the other descendents of the enclosing object". For example

{
  @context { "a" : "http://..."}
  ...
  "a" : {
           "a" : "http://...."
        }
}

means that "a" is expanded in both the top and the enclosed object.

However, you have an example saying

{
  @context {
      "name": "http://xmlns.com/foaf/0.1/name",
      "homepage": "http://xmlns.com/foaf/0.1/homepage",
      "@coerce": 
      {
         "@iri": "homepage"
      }
  }
  ...
}

ie, the expansion of "homepage" is also valid in @coerce, which is not explained by the rule above.

This needs precise spec. Or, alternatively, the @coerce is out of the validity range... (though I think a better spec is better)

------

Reading 3.11, I do not understand it. What is the role of @subject in the outer object in the first example? 

In general, I do not understand what framing tries to achieve. There is no explanation in the text; more precisely, I do not understand the introductory text. I am asking the question that I am also asking below re other features: do we need it for the majority of users? 

------

Reading other emails, I must say I am begining to be in favour of dropping CURIE-s for the time being. It makes reading the document complicated for a non-expert (talking as somebody who uses prefixes all the time:-).

---- 

Section 4.6 I am fairly opposed the idea of overriding keywords. That is really a rope to hang ourselves in terms of readability of a dataset. Also, what are the consequences if the context file is read from the web as an external file? Doesn't it radically change the interpretation of a specific JSON-LD file with or without an access to that context?

----

Section 4.7 I of course understand what normalization is used for, but I seriously question whether this is something we should put into this document. The goal is to reach javascript/web developer people. I think only a very small percentage will make use of this normalization, for the rest this is a complicated noise. I would propose to remove normalization altogether and, if there is a clear view on it, then put it into a separate document.

So, in summary: I believe the spec _is_ a bit too complicated for what we want to achieve. There are features that are probably useful for a minority of users but, I am afraid, if this document is put forward to the non-SW, non-LD, non-RDF community, then it will be rejected as too complex. Normalization, possibly framing should be put into separate documents for niche users...

I am sorry if I sound negative:-(

Ivan

----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Tuesday, 30 August 2011 17:02:47 GMT

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