CORS header not being set

[AlasdairGray]

This issue was discovered when adding JSON-LD support to the validation and is captured in issue ShEx-Validator #36.

To reproduce the error, deploy Validata with the Bioschems configuration file, or use the deployment at http://www.macs.hw.ac.uk/~ajg33/BioschemasValidata/

Click on one of the examples which will add JSON-LD into the Input Data box. Validata should convert this into turtle for validation. If you look in the error console you will see
Access to XMLHttpRequest at 'http://schema.org/' from origin 'http://www.macs.hw.ac.uk' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

What is going on is that when the Input Data box detects that the input is JSON-LD it tries to covert it to turtle. You can see this by entering the following

{
    "@type": "http://schema.org/Person",
    "name": "Jane Doe"
}

If you try the equivalent with an @context statement, then the system tries to pull in the context file dynamically. This fails with the CORS error

{
    "@context": "http://schema.org/",
    "@type": "http://schema.org/Person",
    "name": "Jane Doe"
  }

I have verified that schema.org is able to server the request properly. It is something in the request that is incorrect. I just can’t work out what.

[kcmcleod]

The CORS statement normally goes in the response header from the server and allows the data served to be used by applications from other sites.

Access to XMLHttpRequest at 'http://schema.org/' from origin 'http://www.macs.hw.ac.uk' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Reading the error it looks as though the server (http://schema.org) has no CORS statement in its response header. If this is true, it is a schema.org issue and not a Validator one.

The only to tell is to look at the response header. What is the URI that is being called?

[AlasdairGray]

There is something in the way that schema.org is set up that requires the client to send certain things in the header. There are some details at https://github.com/json-ld/json-ld.org/wiki/existing-contexts

When I use the Chrome CORS extension to inject the appropriate incantations it works. Just need to work out how to get the jQuery to inject them.