Re: GraphQL and SHACL

Thanks Peter.

I see the “user friendliness” of the compact syntax as its main feature. Would you agree?

I looked at the paper and compact syntax that may be proposed in it was not clear to me. Can you provide some examples?

One issue that I see is that SHACL is very rich and expressive. There is typically a conflict between rich/expressive/comprehensive and simple/easy to use. 

It may be that the compact syntax optimized for ease of learning and use would not support full expressivity. In principle, multiple compact syntaxes could be supported - just like RDF has multiple serializations. However, if it was possible to define a syntax that is very user friendly, compact and has full expressivity, this would be great.

Here is what I mean by the user friendly syntax. 

Below is a pure, not extended GraphQL schema example:

# A user account
type User {
 name: String!
 age: Int             
 gender: Gender
 purchases: [Purchase]
}

type Purchase {
 # The internal ID
 productId: String!  
}

enum Gender {
 FEMALE
 MALE
}
The expressivity is less than SHACL - basically, one can describe datatypes and some aspects of cardinality constraints.

However, GraphQL has a “directives” extension point. Using it, we can define, for example,:

# A user account
type User {
 name: String!
 age: Int               @shape(minInclusive: 18)
 gender: Gender
 purchases: [Purchase]
}

type Purchase {
 # The internal ID
 productId: String!     @shape(minLength: 8, pattern: "[0-9]+")
}

enum Gender {
 FEMALE
 MALE
}
This would still be valid GraphQL syntax. The extension elements do not break standard GraphQL parsers and tools.

The definition above would then be equivalent to the following SHACL shapes in Turtle:
ex:User
 a sh:NodeShape ;
 rdfs:comment "A user account" ;
 sh:property [
  sh:path ex:name ;
  sh:datatype xsd:string ;
  sh:maxCount 1 ;
  sh:minCount 1 ;
  sh:order 0 ;
 ] ;
 sh:property [
  sh:path ex:age ;
  sh:datatype xsd:integer ;
  sh:maxCount 1 ;
  sh:minInclusive 18 ;
  sh:order 1 ;
 ] ;
 sh:property [
  sh:path ex:gender ;
  sh:maxCount 1 ;
  sh:node ex:Gender ;
  sh:order 2 ;
 ] ;
 sh:property [
  sh:path ex:purchases ;
  sh:node ex:Purchase ;
  sh:order 3 ;
 ] .

ex:Purchase
 a sh:NodeShape ;
 sh:property [
  sh:path ex:productId ;
  sh:datatype xsd:string ;
  sh:description "The internal ID" ;
  sh:maxCount 1 ;
  sh:minCount 1 ;
  sh:minLength 8 ;
  sh:pattern "[0-9]+" ;
  sh:order 0 ;
 ] .
 
ex:Gender
 a sh:NodeShape ;
 sh:in ( "FEMALE" "MALE" ) .
We have this working already and in use with extensive models that contain thousands of shapes.

Regards,

Irene

> On Jun 19, 2018, at 2:45 PM, Peter F. Patel-Schneider <pfpschneider@gmail.com> wrote:
> 
> The paper "Semantics and Validation of Recursive SHACL"
> by Julien Corman, Juan L. Reutter, and Ognjen Savković has the beginnings of a compact 
> syntax for SHACL.   It looks quite good to me.
> 
> An extended version of the paper is available at
> https://www.inf.unibz.it/krdb/KRDB%20files/tech-reports/KRDB18-01.pdf
> 
> peter
>  
> 
> 
> On 06/19/2018 07:36 AM, Irene Polikoff wrote:
>> One of the capabilities for SHACL that is not yet standardized is a compact
>> syntax. As part of the WG effort, a draft of the proposed compact syntax was
>> developed, but, due to the time constraints, finalizing this work was deemed
>> out of scope and to be addressed in the community group.
>> 
>> In the last 6 months or so we, at TopQuadrant, have been experimenting with
>> the use of GraphQL and GraphQL schemas. GraphQL is already widely used and
>> interest in it is rapidly growing. We see its design and capabilities as
>> well aligned with SHACL, making it possible (among other things) to use
>> GraphQL as a compact syntax for SHACL.
>> 
>> Results of our work will be presented in upcoming
>> webinars: https://www.topquadrant.com/graphql-webinar/ this Thursday June
>> 21st (9 am EDT) and also next week, Friday, June 29th (4pm EDT) - 2
>> timeslots are available to better accommodate different time zones. However,
>> both webinars will cover the same content.
>> 
>> If you are interested in this topic, please join the webinars and provide
>> feedback.
>> 
>> Regards,
>> 
>> Irene Polikoff
>