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Re: Official response to RDF-ISSUE-132: JSON-LD/RDF Alignment -- Sub-issue on the relationship between JSON-LD and RDF

From: David Booth <david@dbooth.org>
Date: Tue, 11 Jun 2013 00:17:27 -0400
Message-ID: <51B6A4D7.5040004@dbooth.org>
CC: 'public-rdf-comments' <public-rdf-comments@w3.org>
Below is a specific proposal for resolving the issue that the normative 
relationship between JSON-LD and RDF is not clear, and the JSON-LD model 
is not fully aligned with the RDF model.  It clarifies that JSON-LD is a 
concrete syntax for RDF and ensures complete alignment with RDF while 
avoiding additional early mentions of RDF in the document.

For substantive changes:

1. In RDF conversion algorithms in JSON-LD 1.0 Processing Algorithms and 
API,
http://json-ld.org/spec/latest/json-ld-api/#rdf-conversion-algorithms
specify that **when JSON-LD is interpreted as RDF,** (i.e., when the 
JSON-LD model is converted to the RDF model) skolem IRIs MUST be 
generated using the well-known URI suffix "json-ld-genid" for any 
JSON-LD blank node that would otherwise be mapped to an RDF blank node 
in a position where an RDF blank node is not permitted.  Conversely, 
when RDF is serialized as JSON-LD (or when an RDF model is converted to 
a JSON-LD model), skolem IRIs having the well-known URI suffix 
"json-ld-genid" SHOULD be serialized as JSON-LD blank nodes.  Finally, 
register the well-known URI suffix "json-ld-genid", in accordance with 
RFC5785:
http://tools.ietf.org/html/rfc5785
BACKGROUND NOTE: The existing well-known URI suffix "genid" is for 
converting to/from RDF blank nodes (in positions where blank nodes are 
*permitted* in RDF), whereas "json-ld-genid" will be used for *avoiding* 
blank nodes (in positions where they are not allowed in RDF).

2. Make any other changes needed to ensure that JSON-LD is a normative 
concrete syntax for RDF.  (Are any other changes needed?)

For editorial changes:

3. In section 1
https://dvcs.w3.org/hg/json-ld/raw-file/default/spec/latest/json-ld/index.html#introduction
make the following editorial change to clarify and move the mention of 
RDF slightly later in the document.  Delete the sentence: "Developers 
that require any of the facilities listed above or need to serialize an 
RDF graph or dataset [RDF11-CONCEPTS] in a JSON-based syntax will find 
JSON-LD of interest.".  Instead, add the following bullet item to the 
existing bullet list in section 1.1:

  - "Software developers who want to generate or consume Linked
    Data, an RDF graph or an RDF Dataset in a JSON syntax."

4. Without adding any earlier mention of RDF than the JSON-LD spec 
already contains, make other editorial changes as needed to avoid 
implying that JSON-LD is not necessarily RDF.  (However it is fine to 
say that JSON-LD does not need to be *processed* as RDF.)  Some examples:

  - Change "Converting JSON-LD to RDF" to either "Interpreting JSON-LD 
as RDF" or "Converting a JSON-LD model to an RDF model".

  - Change "Convert to RDF Algorithm" to "Interpret as RDF Algorithm" or 
"Algorithm for Interpreting JSON-LD as RDF".

  - Change "Convert from RDF Algorithm" to "Serialize from RDF 
Algorithm" or "Algorithm for Serializing RDF as JSON-LD".

  - Change "This algorithms converts a JSON-LD document to an RDF 
dataset" to "This algorithm interprets a JSON-LD document as an RDF 
dataset".

  - Change "This algorithm converts an RDF dataset" to "This algorithm 
serializes an RDF dataset".

  - Change "turning a JSON-LD document" to "interpreting a JSON-LD 
document as RDF".

There are many other instances in the JSON-LD document, and I would be 
happy to help find and fix them.  Most of them can be found by searching 
for the verb "convert" and changing it to "interpret" or "serialize". 
Alternatively you could say "deserialize" instead of "interpret".

5. At the beginning of appendix C insert: "JSON-LD is a _concrete RDF 
syntax_ as described in [RDF11_CONCEPTS].  Hence, a JSON-LD document is 
both an RDF document and a JSON document and correspondingly represents 
both an instance of the RDF data model and an instance of the JSON-LD 
data model."

6. In appendix C change the following paragraph in accordance with #1 above:
[[
Summarized these differences mean that JSON-LD is capable of serializing 
any RDF graph or dataset and most, but not all, JSON-LD documents can be 
directly transformed to RDF. It is possible to work around this 
restriction, when converting JSON-LD to RDF, by converting blank nodes 
used as graph names or properties to IRIs, minting new "Skolem IRIs" as 
per Replacing Blank Nodes with IRIs of [RDF11-CONCEPTS]. A complete 
description of the algorithms to convert from RDF to JSON-LD and from 
JSON-LD to RDF is included in the JSON-LD Processing Algorithms and API 
specification [JSON-LD-API].
]]

to:
[[
The algorithm for interpreting JSON-LD as RDF is specified in the 
JSON-LD Processing Algorithms and API specification [JSON-LD-API], which 
is hereby normatively included by reference.
]]

7. In section C.1
https://dvcs.w3.org/hg/json-ld/raw-file/default/spec/latest/json-ld/index.html#transformation-from-json-ld-to-rdf
make the following changes:

a. Change the title from "Transformation from JSON-LD to RDF" to "Brief 
Overview of Interpreting JSON-LD as RDF".

b. After "This section is non-normative." add: "The complete, normative 
algorithm for interpreting JSON-LD as RDF is defined in the JSON-LD 
Processing Algorithms and API specification [JSON-LD-API] secion 10."

Thanks,
David
Received on Tuesday, 11 June 2013 04:18:00 UTC

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