Re: shapes-ISSUE-60 (Other Extension Languages): Shall SHACL support other extension languages beside SPARQL (like JavaScript)? [SHACL Spec]

Thinking a bit more about JavaScript support for SHACL, I believe the 
following syntax would be quite attractive and is easy to implement:

     sh:constraint [
         sh:message "The URL {?value} cannot be resolved for {?predicate}" ;
         sh:predicate ex:imageURL ;
         sh:jsExpression "helper.isResolvableMedia(value)" ;
         sh:jsLibrary "" ;
     ] .

If a constraint has a sh:jsExpression, then the system would walk 
through all values of the provided sh:predicate and invoke 
sh:jsExpression with the given object pre-assigned to the JavaScript 
variable "value". The example above would call a helper function, but 
this could be any JavaScript snippet that returns a boolean result. If 
false, a constraint violation is produced using the sh:message template. 
sh:jsLibrary would point at a required JavaScript file that the engine 
needs to use. I implemented something very similar with SPINx [1] and it 
works quite well with embedded JavaScript APIs such as Mozilla Rhino 
[2]. The example above could of course also be turned into a SHACL 
template, so that the actual JavaScript details get hidden, and people 
just instantiate

     sh:constraint [
         a lib:ResolvableMediaConstraint ;
         lib:predicate ex:imageURL ;
     ] .

This approach could be in addition to the JSON-LD approach suggested by 
Arthur (which has higher implementation costs but is more general). 
Maybe the IBM people who championed this topic could provide feedback.

In general I believe we have an immense opportunity here to create 
something that could propel Semantic Technology into much more 
mainstream use cases, as a schema language for JavaScript applications, 
and servers using JSON for data exchange and interface definitions. 
JavaScript also covers additional use cases that cannot be expressed in 



On 5/30/2015 11:48, RDF Data Shapes Working Group Issue Tracker wrote:
> shapes-ISSUE-60 (Other Extension Languages): Shall SHACL support other extension languages beside SPARQL (like JavaScript)? [SHACL Spec]
> Raised by: Holger Knublauch
> On product: SHACL Spec
> We have frequently discussed that there could be other extension languages beside SPARQL, but I don't think we ever formally closed this topic. The current spec would allow other languages such as JavaScript, identified through some property such as shjs:js. My impression from discussions in the WG was that most people would be in favour of allowing this flexibility, but I believe Peter was against that. In any case, we need a resolution.
> Once we do that, we could discuss whether we also want to do a JavaScript deliverable as part of the WG, but that would be a separate ticket.

Received on Sunday, 31 May 2015 05:16:41 UTC