Re: Schema Salad

* Peter Amstutz <peter.amstutz@curoverse.com> [2015-09-08 13:31-0400]
> Neat!  I haven't seen much in the way of technologies for strict
> validation for RDF structures so it is useful to see work on this
> problem.  Salad is intended as a higher level source document from
> which concrete schemas are derived, so Shape Expressions could be a
> transformation target to use a salad schema to validate data directly
> as triples.

ShEx has a JSON representation. ShEx compact syntax files
  https://github.com/shexSpec/shexTest/tree/master/schemas
translate the corresponding JSON files:
  https://github.com/shexSpec/shexTest/tree/master/parsedSchemas

I wonder if you could generate JSON from your python code and invoke
an external ShEx validator. I put together a validate scripe for you
to try out:

  npm install shex
  ./node_modules/shex/bin/validate -n http://a.example/s myPersonSchema.shex somePerson.ttl

That says to validate the node <http://a.example/s> in somePerson.ttl
as whatever the start rule is in myPersonSchema.shex. This is not
really ready for release as it gives 0 error messages, but unless you
tell it to be quiet (-q), you'll get output that tells you how the
triples in the data matched the rules in ShEx. I've attached the two
input files myPersonSchema.shex and somePerson.ttl so you have a gentle
start.


> The use case for Salad is aimed at the problem of creating
> document/message formats that are usable as both idiomatic JSON and
> can be interpreted as JSON-LD to yield triples.  This turns out to be
> somewhat tricky since JSON-LD has some quirks and limitations that
> prevent it from being used to mark up totally arbitrary idiomatic
> JSON, so Salad is designed to facilitate a design that ensures the two
> interpretations are consistent, no relevant information is lost during
> conversion, and are the resulting format is convenient for humans to
> read and write.

I note that your work is in python. Perhaps Harold Solbrig's RDFLib
ShEx stuff will be useful to you.


> Thanks,
> Peter
> 
> On Tue, Sep 8, 2015 at 1:04 PM, David Booth <david@dbooth.org> wrote:
> > On 09/07/2015 09:33 PM, Peter Amstutz wrote:
> >>
> >> I wanted to introduce a project I am working on, "Schema Salad":
> >> https://github.com/common-workflow-language/schema_salad
> >
> >
> > Sounds very interesting!   You might want to look at Shape Expressions
> > (ShEx) also, if you haven't seen it:
> > http://www.w3.org/2013/ShEx/Primer
> >
> > ShEx is not JSON-specific, but can validate RDF or even transform it.
> >
> > David Booth
> >
> >
> >>
> >> Salad is a schema language for describing structured linked data
> >> documents in JSON or YAML documents. A Salad schema provides rules for
> >> preprocessing, structural validation, and link checking for documents
> >> described by a Salad schema. Salad builds on JSON-LD and the Apache
> >> Avro data serialization system, and extends Avro with features for
> >> rich data modeling such as inheritance, template specialization,
> >> object identifiers, and object references. Salad was developed to
> >> provide a bridge between the record oriented data modeling supported
> >> by Apache Avro and the Semantic Web.
> >>
> >> The JSON data model is an extremely popular way to represent
> >> structured data. It is attractive because of it's relative simplicity
> >> and is a natural fit with the standard types of many programming
> >> languages. However, this simplicity means that basic JSON lacks
> >> expressive features useful for working with complex data structures
> >> and document formats, such as schemas, object references, and
> >> namespaces.
> >>
> >> JSON-LD is a W3C standard providing a way to describe how to interpret
> >> a JSON document as Linked Data by means of a "context". JSON-LD
> >> provides a powerful solution for representing object references and
> >> namespaces in JSON based on standard web URIs, but is not itself a
> >> schema language. Without a schema providing a well defined structure,
> >> it is difficult to process an arbitrary JSON-LD document as idiomatic
> >> JSON because there are many ways to express the same data that are
> >> logically equivalent but structurally distinct.
> >>
> >> Several schema languages exist for describing and validating JSON
> >> data, such as the Apache Avro data serialization system, however none
> >> understand linked data. As a result, to fully take advantage of
> >> JSON-LD to build the next generation of linked data applications, one
> >> must maintain separate JSON schema, JSON-LD context, RDF schema, and
> >> human documentation, despite significant overlap of content and
> >> obvious need for these documents to stay synchronized.
> >>
> >> Schema Salad is designed to address this gap. It provides a schema
> >> language and processing rules for describing structured JSON content
> >> permitting URI resolution and strict document validation. The schema
> >> language supports linked data through annotations that describe the
> >> linked data interpretation of the content, enables generation of
> >> JSON-LD context and RDF schema, and production of RDF triples by
> >> applying the JSON-LD context. The schema language also provides for
> >> robust support of inline documentation.
> >>
> >> This is a work in progress, and any comments, suggestions, or pointers
> >> to related/similar technologies would be very much appreciated.  Here
> >> are a couple of example schemas:
> >>
> >>
> >> https://github.com/common-workflow-language/schema_salad/blob/master/schema_salad/metaschema.yml
> >>
> >>
> >> https://github.com/common-workflow-language/common-workflow-language/blob/salad_schema/schemas/draft-3/cwl-avro.yml
> >>
> >> Thanks,
> >> Peter
> >>
> >>
> >>
> >>
> >

-- 
-ericP

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