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Re: Structural validation with JSON-schema and JSON-LD Framing

From: Brent Shambaugh <brent.shambaugh@gmail.com>
Date: Sat, 14 Mar 2015 13:13:29 -0500
Message-ID: <CACvcBVqeb9aex-GpYr3caX34KDfaRf5R3KuFRboYSkuG-NE6Ow@mail.gmail.com>
To: Nate Otto <nate@ottonomy.net>
Cc: Linked JSON <public-linked-json@w3.org>, Credentials Community Group <public-credentials@w3.org>
Nate,

Here is another response that I got when digging into Agent.js. @ahdinosaur
claimed that he wrote an extension for linked data for json-schema (
https://github.com/openvocab/ovn/issues/13#issuecomment-79457550). Elf
Palvik may be participating in this too. I've seen both of them in and
around this community.

-Brent Shambaugh

Website: bshambaugh.org

On Thu, Mar 12, 2015 at 9:01 PM, Brent Shambaugh <brent.shambaugh@gmail.com>
wrote:

> Fun! I was just looking at some JSON that I wanted to write JSON-LD for
> and I turned to a JavaScript Developer wondering what "$ref:
> "Relationship"" meant. It turned out that he thought I was reading JSON
> Schema. Maybe we'll intersect someday. FWIW it was here (
> https://github.com/openvocab/ovn/blob/master/vocab/Agent.js).
>
> -Brent Shambaugh
>
> Website: bshambaugh.org
>
> On Mon, Mar 9, 2015 at 5:16 PM, Nate Otto <nate@ottonomy.net> wrote:
>
>> JSON-LD community,
>> (CC Credentials Community Group & Badge Alliance)
>>
>> In the Badge Alliance, we've been preparing a new draft of our Open
>> Badges spec that uses JSON-LD. We are experimenting with the idea of
>> "extensions", where badge issuers may collaborate on sets of additional
>> properties to add to badges. An extension is more than just adding new
>> linked data properties to a badge; it's about making sure that many issuers
>> can add the same type of data to a badge for a purpose, in a consistent
>> manner, to make it more likely that consumers would implement understanding
>> those additions in their products. See our draft here:
>> http://specification.openbadges.org/#Extensions
>>
>> For example, a badge assertion itself would have a context at the top,
>> and an issuer may add an extension as an embedded JSON object (blank node)
>> with its own context link:
>>
>> {
>>   "@context": "http://specification.openbadges.org/1.1/context.json",
>>
>>   .... badges properties ....
>>
>>   "extension:exampleExtension": {
>>     "@context":"
>> http://standard.openbadges.org/extensions/exampleExtension/context.json",
>>     "@type": ["extension", "extension:ExampleExtension"],
>>     "exampleProperty": "I'm a property, short and sweet."
>>   }
>> }
>>
>> We wanted to be able to answer the question "did the issuer implement the
>> extension how the extension author intended?" For that, we turned to
>> JSON-schema (http://json-schema.org/), which allows authors to set out
>> what the structure of an extension should be so that implementers know what
>> properties must be includes, what data types are permitted, and have a
>> built-in validation method to ensure that they have correctly implemented
>> the specification.
>>
>> Within the context for an extension, there is a obi:validation array that
>> contains references to different JSON-schema validators relevant to
>> documents that use the context.
>>
>> {
>>   "@context": {
>>     "obi": "http://standard.openbadges.org/",
>>     "exampleProperty": "http://schema.org/text"
>>   },
>>   "obi:validation": [
>>     {
>>       "obi:validatesType": "obi:extensions/#ExampleExtension",
>>       "obi:validationSchema": "http://standard.openbadges.org/extensions/exampleExtension/schema.json"
>>     }
>>   ]
>> }
>>
>> The obi:validatesType property provides a key to what objects within an
>> Open Badge the obi:validationSchema applies to. Processors who want to take
>> advantage of the optional JSON-schema features would be instructed to
>> extract the JSON object(s) corresponding to the type from the input badge
>> object and process them against the schema.
>>
>> The current approach (not finalized) instructed extension authors to
>> write JSON-schema based on the compact JSON input they expected to see.
>> Manu Sporny provided us some feedback that I'd like to discuss a little
>> more here, that we should use a JSON-LD frame to process the input JSON
>> into a compact form to be used as input to a JSON-schema validation process.
>>
>> JSON-LD framing is powerful for a case like this. A simple frame like:
>>
>> {
>> "@context:" "http://appropriatecontext.com",
>>   "@type":"extension:ExampleExtension"
>> }
>>
>> ...could pull out just the extensions that apply and test them.
>>
>> The downsides of this approach are mostly around the difficulty of
>> learning JSON-LD and JSON-LD framing for developers. Without adding a
>> JSON-LD framing step to the validation process, implementations don't
>> necessarily need a JSON-LD processor as part of their Open Badges
>> processing stack, but if we add Framing, they will be required to include
>> JSON-LD processing. In addition, extension authors will need to learn
>> Framing in order to write validation features of extensions, and there are
>> precious few examples of JSON-LD frames in the wild, most from late 2011,
>> and I don't know if they are up-to-date. I've struggled to write any frame
>> more complex than the above, for instance, after 7 months of casually
>> studying JSON-LD. While some of the core Badge Alliance members may be able
>> to provide some support to extension authors, I don't want this to become a
>> major impediment to the growth of the specification.
>>
>> However, what is more important is that we find a beautiful combination
>> of technologies that gives Open Badges and open credentials a productive
>> long future life. I'd love some feedback on connecting JSON-LD with
>> JSON-schema, and particularly about whether Framing should be included as a
>> step in this process.
>>
>> *Nate Otto, Developer*
>> concentricsky.com
>>
>
>
Received on Saturday, 14 March 2015 18:13:58 UTC

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