W3C home > Mailing lists > Public > public-linked-json@w3.org > August 2015

Trailing content in JSON-LD

From: Andy Seaborne <andy@seaborne.org>
Date: Sun, 23 Aug 2015 11:15:42 +0100
Message-ID: <55D99D4E.5050702@seaborne.org>
To: Linked JSON <public-linked-json@w3.org>
I'm having trouble pinning down what the spec status is of this input 
(this is for an issue in jsonld-java).

Does the trailing content mean it is illegal JSON-LD or not or is it 
outside the spec altogether in some cases?

----------------------
{
   "@id" : "http://example/s",
   "http://example/p" : "str"
}
xxxxxxxxx
----------------------

The question is whether the whole input is the "JSON Document" or 
whether the trailing junk is considered to be outside the JSON Document.

In the first case, it is a parse error, and any output is undefined.
In the second case, there would be triples and no parse error.

I currently think that the spec says this is illegal JSON-LD but the 
argument is convoluted and relies on the input coming from HTTP.  If it 
were some other source (a file with a non jsonld extension [tut, tut]), 
it is unstated.

The spec chase:

Section 8 =>

"""
A JSON-LD document MUST be a valid JSON document as described in [RFC4627].

A JSON-LD document MUST be a single node object or an array whose 
elements are each node objects at the top level.
"""

RFC4627 is the media type registration for JSON.

The definition link for "JSON-LD document" is descriptive:
"""
A JSON-LD document serializes a generalized RDF Dataset 
[RDF11-CONCEPTS], which is a collection of graphs that comprises exactly 
one default graph and zero or more named graphs.
"""

so it does not say, to my reading, that the "JSON-LD document" includes 
or excludes the content after the "}".

RFC4627 talks about a "JSON text" when defining the media type.
Because that is the whole of the HTTP body, I think it means that "JSON 
text" includes everything. Then "MUST be a single node object" applies 
=> it's a parse error.

Proposed spec fix 1:
If it said that
"""
A JSON-LD document MUST be a valid JSON *text* as described in [RFC4627].
"""

then it would be clearer but still only applies if the media type can be 
invoked and sometimes it can't (e.g a stream of chars from a non-HTTP 
stream).



A sentence in the grammar explicitly, making it a synatx isse, not a 
context issue, stating that no trailing content is permitted would cover 
all cases.

	Andy
Received on Sunday, 23 August 2015 10:16:13 UTC

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